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Digital cameras at low temperatures

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Anonymous
May 24, 2005 7:31:49 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Some time back there was a thread about using digital cameras below
zero, and IIRC the consensus was that - 20C was about the limit, for
batteries as well.

Last night the local camera club invited a guest to show us his images
of his 2004 Everest climb. He used a Sony (I think) compact, no model
mentioned, but he chose it because it used AA batteries, and he took a
supply of AA lithiums.

Apart from the breathtaking scenery, projected with a high-end digital
projector, the gradation and detail in the snow textures had me thinking
at first that these were scanned film shots, but he assured us that they
were digital images, beautifully - if automatically - exposed.

He remarked that at the higher altitudes, it was all he could do to
remember to take the shots, let alone think about exposures, and he
mentioned several shots that he just didn't think to take, like himself
on the summit.

But, as the subject line mentions, he said the temperatures above 8,000
metres were between -35C to -40C, and the camera continued to function,
except that at the very coldest, the focusing froze, and some of the
shots were out of focus.

So it appears that -20C is certainly not the limit for digital cameras.

Colin.
May 24, 2005 7:31:50 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

If you keep the camera close to your body and take it out for a few shots,
they will work OK. The electronics are much tougher than the batteries.
Last winter in a cold -30°C windy day, the batteries in our 10D would only
last a few shots and then the camera would die. The camera would stay up
about 15 minutes outside at the most. When we brought the camera in from
the cold, the battery would recover as it warmed up.

Jean

"Colin D" <ColinD@killspam.127.0.0.1> a écrit dans le message de
news:4292A025.19B1EA40@killspam.127.0.0.1...
> Some time back there was a thread about using digital cameras below
> zero, and IIRC the consensus was that - 20C was about the limit, for
> batteries as well.
>
> Last night the local camera club invited a guest to show us his images
> of his 2004 Everest climb. He used a Sony (I think) compact, no model
> mentioned, but he chose it because it used AA batteries, and he took a
> supply of AA lithiums.
>
> Apart from the breathtaking scenery, projected with a high-end digital
> projector, the gradation and detail in the snow textures had me thinking
> at first that these were scanned film shots, but he assured us that they
> were digital images, beautifully - if automatically - exposed.
>
> He remarked that at the higher altitudes, it was all he could do to
> remember to take the shots, let alone think about exposures, and he
> mentioned several shots that he just didn't think to take, like himself
> on the summit.
>
> But, as the subject line mentions, he said the temperatures above 8,000
> metres were between -35C to -40C, and the camera continued to function,
> except that at the very coldest, the focusing froze, and some of the
> shots were out of focus.
>
> So it appears that -20C is certainly not the limit for digital cameras.
>
> Colin.
Anonymous
May 24, 2005 7:31:50 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Colin D wrote:
> Some time back there was a thread about using digital cameras below
> zero, and IIRC the consensus was that - 20C was about the limit, for
> batteries as well.
>
> Last night the local camera club invited a guest to show us his images
> of his 2004 Everest climb. He used a Sony (I think) compact, no model
> mentioned, but he chose it because it used AA batteries, and he took a
> supply of AA lithiums.
>
> Apart from the breathtaking scenery, projected with a high-end digital
> projector, the gradation and detail in the snow textures had me thinking
> at first that these were scanned film shots, but he assured us that they
> were digital images, beautifully - if automatically - exposed.
>
> He remarked that at the higher altitudes, it was all he could do to
> remember to take the shots, let alone think about exposures, and he
> mentioned several shots that he just didn't think to take, like himself
> on the summit.
>
> But, as the subject line mentions, he said the temperatures above 8,000
> metres were between -35C to -40C, and the camera continued to function,
> except that at the very coldest, the focusing froze, and some of the
> shots were out of focus.
>
> So it appears that -20C is certainly not the limit for digital cameras.
>
> Colin.

No, in fact, digital cameras work BETTER when they get cold as noise
levels drop dramatically. The issues are the focusing mechanism, as you
mentioned, and the batteries. If the batteries are kept warm, and
focusing isn't a problem (a fixed focus camera might be better under
such hostile conditions), then the digital camera will get BETTER
pictures in cold conditions.


--
Ron Hunter rphunter@charter.net
Related resources
Anonymous
May 24, 2005 7:31:50 PM

Archived from groups: rec.photo.digital (More info?)

On Tue, 24 May 2005 15:31:49 +1200, Colin D wrote:

> But, as the subject line mentions, he said the temperatures above 8,000
> metres were between -35C to -40C, and the camera continued to function,
> except that at the very coldest, the focusing froze, and some of the
> shots were out of focus.
>
> So it appears that -20C is certainly not the limit for digital cameras.

If you check the Energizer Lithium AA packages, you'll see that
they state that their operating temperature range is as low as 40
below (ºF or ºC). Different cameras may have different temperature
tolerances. As such low temperatures might cause problems with LCD
displays (it might make them extremely sluggish at best) it may be
best to use cameras with optical viewfinders rather than those with
EVF's or no viewfinders at all.
Anonymous
May 24, 2005 7:31:50 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

On Tue, 24 May 2005 04:31:49 +0100, Colin D wrote:
>
> So it appears that -20C is certainly not the limit for digital cameras.
>
During high altitude climbing people don't hang the cameras around their
neck. Usually they are kept in one of the inside pockets of the down-suite
where it remains close to the body temperature. People will get their
camera out, get a few shots in quick succession and put the camera back
again. During climbing one of the high peaks, you are struggling to get
breath and avoid fall, thought of taking an artistic picture does not come
to mind. Once the camera is out, it will function for 10-20 minutes,
depending on the ambient temperature & more importantly the wind chill
factor. Quite often when the actual temperature is -20C, wind chill factor
would make it more like -70C. Focusing motor may function for a while but
the lens barrel, being exposed directly to the elements, would freeze very
quickly. Around the high peaks on a decent day the air is so clear & free
of dust that very ordinary cameras can take excellent pictures. I doubt
very much that cooling of the sensor has anything to do with it. By the
time the sensor is cooling down to a noise-suppressing level, the rest of
the camera, including its shutter mechanism would probably be frozen.

--

Gautam Majumdar

Please send e-mails to gmajumdar@freeuk.com
Anonymous
May 24, 2005 7:31:50 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"Colin D" <ColinD@killspam.127.0.0.1> wrote in message
news:4292A025.19B1EA40@killspam.127.0.0.1...
> Apart from the breathtaking scenery, projected with a high-end digital
> projector, the gradation and detail in the snow textures had me thinking
> at first that these were scanned film shots, but he assured us that they
> were digital images, beautifully - if automatically - exposed.

Don't be silly anyone knows that the only way to view quality photos is with
slide film. Just ask duncan j murray and co.

> He remarked that at the higher altitudes, it was all he could do to
> remember to take the shots, let alone think about exposures, and he
> mentioned several shots that he just didn't think to take, like himself
> on the summit.
>
> But, as the subject line mentions, he said the temperatures above 8,000
> metres were between -35C to -40C, and the camera continued to function,
> except that at the very coldest, the focusing froze, and some of the
> shots were out of focus.
>
> So it appears that -20C is certainly not the limit for digital cameras.
>
> Colin.

Not so much the camera as the battery technology.
Anonymous
May 24, 2005 7:31:50 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Colin D wrote:


> But, as the subject line mentions, he said the temperatures above 8,000
> metres were between -35C to -40C, and the camera continued to function,
> except that at the very coldest, the focusing froze, and some of the
> shots were out of focus.
>
> So it appears that -20C is certainly not the limit for digital cameras.

A human being will die fairly quickly at -35 to -40C. How did
these people survive :-)

I think we can be certain he wasn't carrying the camera out in
the open at these temperatures. Keeping it tucked under many
layers of warm clothing would guarantee the core of the camera
never got much below freezing.

It does get down to -40C where I live.. I've had my Canon 10D out
on a tripod for 1/2 an hour at -32C (-24F) taking snowy landscape
shots illuminated by the full moon).

The camera was so cold, icy frost crystals would form on
the body from my breath. It worked fine and suffered
no ill effects.
Anonymous
May 24, 2005 7:31:51 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"Gautam Majumdar" <gmajumdar@XSPAMfreeuk.com> wrote in message
news:2gAke.120360$Cq2.61723@fe2.news.blueyonder.co.uk...
> On Tue, 24 May 2005 04:31:49 +0100, Colin D wrote:
>>
>> So it appears that -20C is certainly not the limit for digital cameras.
>>
> During high altitude climbing people don't hang the cameras around their
> neck. Usually they are kept in one of the inside pockets of the down-suite
> where it remains close to the body temperature. People will get their
> camera out, get a few shots in quick succession and put the camera back
> again. During climbing one of the high peaks, you are struggling to get
> breath and avoid fall, thought of taking an artistic picture does not come
> to mind. Once the camera is out, it will function for 10-20 minutes,
> depending on the ambient temperature & more importantly the wind chill
> factor. Quite often when the actual temperature is -20C, wind chill factor
> would make it more like -70C. Focusing motor may function for a while but
> the lens barrel, being exposed directly to the elements, would freeze very
> quickly. Around the high peaks on a decent day the air is so clear & free
> of dust that very ordinary cameras can take excellent pictures. I doubt
> very much that cooling of the sensor has anything to do with it. By the
> time the sensor is cooling down to a noise-suppressing level, the rest of
> the camera, including its shutter mechanism would probably be frozen.

I thought the wind chill factor only affected something coated in water or
something generating heat. Its the ability of air to conduct heat away from
the body and the gradient. The steeper the temp difference the faster heat
will transfer. As transference occurs the medium (this case air) heats up,
thus the temp differential is reduced and thus thermal conductivity is
reduced. The greater the air movement basically means the more changes of
air in a given space of time. The other part of windchill is water
evapouration. Water evapourating draws energy. So now you have relative
moisture levels included that behave the same way as relative temperature
levels.

So where is all this going? Well consider this last fact, a fan isn't
moving "cool air" for the most part the air is the same temperature it
doesn't magically become cooler as it passes through a fan as such, its
evapouration of sweat. Water does not cool, evapourating water does. So
humid conditions tend to feel hotter as there is less evapouration. Water
is actually a good insulator, ask any wetsuit owner.

"So what?" i hear you ask. Well the camera will remain at the ambient
temperature. It is not losing heat, it is not generating any to lose. Nor
does it sweat. Condensation freezing is the most likely cause of a jammed
auto focus. Then of course any lubricants. So whatever the ambient
temperature is that the the temp of the camera or any other inanimate
object. Windchill is irrelevant.
Anonymous
May 24, 2005 7:31:51 PM

Archived from groups: rec.photo.digital (More info?)

ASAAR wrote:


> If you check the Energizer Lithium AA packages, you'll see that
> they state that their operating temperature range is as low as 40
> below (ºF or ºC).

I have a wireless outdoor thermometer.. It uses a sensor/transmitter
placed outdoors powered by lithium AA cells. It transmits the
temperature to a receiver/display in the house.

It reported -40C a couple of times last winter and never
quit working..
Anonymous
May 24, 2005 7:31:52 PM

Archived from groups: rec.photo.digital (More info?)

On Tue, 24 May 2005 12:45:58 GMT, ian lincoln wrote:

> "So what?" i hear you ask. Well the camera will remain at the ambient
> temperature. It is not losing heat, it is not generating any to lose. Nor
> does it sweat. Condensation freezing is the most likely cause of a jammed
> auto focus. Then of course any lubricants. So whatever the ambient
> temperature is that the the temp of the camera or any other inanimate
> object. Windchill is irrelevant.

Well, not really. You're correct that windchill measurements are
based on evaporation of water and as you note, cameras don't sweat,
so there's no "windchill" effect occuring. But the camera is much
warmer than the ambient temperature, having been kept near the body.
And if there's any wind at all, the camera is bound to reach ambient
temperature quicker than if there's no wind. That's why air is
usually forced over radiator fins, even though as far as I'm aware,
none have ever been observed sweating. :) 
Anonymous
May 24, 2005 7:31:52 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

ian lincoln wrote:
> "Gautam Majumdar" <gmajumdar@XSPAMfreeuk.com> wrote in message
> news:2gAke.120360$Cq2.61723@fe2.news.blueyonder.co.uk...
>
>>On Tue, 24 May 2005 04:31:49 +0100, Colin D wrote:
>>
>>>So it appears that -20C is certainly not the limit for digital cameras.
>>>
>>
>>During high altitude climbing people don't hang the cameras around their
>>neck. Usually they are kept in one of the inside pockets of the down-suite
>>where it remains close to the body temperature. People will get their
>>camera out, get a few shots in quick succession and put the camera back
>>again. During climbing one of the high peaks, you are struggling to get
>>breath and avoid fall, thought of taking an artistic picture does not come
>>to mind. Once the camera is out, it will function for 10-20 minutes,
>>depending on the ambient temperature & more importantly the wind chill
>>factor. Quite often when the actual temperature is -20C, wind chill factor
>>would make it more like -70C. Focusing motor may function for a while but
>>the lens barrel, being exposed directly to the elements, would freeze very
>>quickly. Around the high peaks on a decent day the air is so clear & free
>>of dust that very ordinary cameras can take excellent pictures. I doubt
>>very much that cooling of the sensor has anything to do with it. By the
>>time the sensor is cooling down to a noise-suppressing level, the rest of
>>the camera, including its shutter mechanism would probably be frozen.
>
>
> I thought the wind chill factor only affected something coated in water or
> something generating heat. Its the ability of air to conduct heat away from
> the body and the gradient. The steeper the temp difference the faster heat
> will transfer. As transference occurs the medium (this case air) heats up,
> thus the temp differential is reduced and thus thermal conductivity is
> reduced. The greater the air movement basically means the more changes of
> air in a given space of time. The other part of windchill is water
> evapouration. Water evapourating draws energy. So now you have relative
> moisture levels included that behave the same way as relative temperature
> levels.
>
> So where is all this going? Well consider this last fact, a fan isn't
> moving "cool air" for the most part the air is the same temperature it
> doesn't magically become cooler as it passes through a fan as such, its
> evapouration of sweat. Water does not cool, evapourating water does. So
> humid conditions tend to feel hotter as there is less evapouration. Water
> is actually a good insulator, ask any wetsuit owner.
>
> "So what?" i hear you ask. Well the camera will remain at the ambient
> temperature. It is not losing heat, it is not generating any to lose. Nor
> does it sweat. Condensation freezing is the most likely cause of a jammed
> auto focus. Then of course any lubricants. So whatever the ambient
> temperature is that the the temp of the camera or any other inanimate
> object. Windchill is irrelevant.
>
>
If that were true, then there would be no point in putting a fan in a
freezer, would there? Of COURSE wind chill matters!


--
Ron Hunter rphunter@charter.net
Anonymous
May 24, 2005 7:31:53 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Ron Hunter wrote:

> ian lincoln wrote:
>
>> "Gautam Majumdar" <gmajumdar@XSPAMfreeuk.com> wrote in message
>> news:2gAke.120360$Cq2.61723@fe2.news.blueyonder.co.uk...
>>
>>> On Tue, 24 May 2005 04:31:49 +0100, Colin D wrote:
>>>
>>>> So it appears that -20C is certainly not the limit for digital cameras.
>>>>
>>>
>>> During high altitude climbing people don't hang the cameras around their
>>> neck. Usually they are kept in one of the inside pockets of the
>>> down-suite
>>> where it remains close to the body temperature. People will get their
>>> camera out, get a few shots in quick succession and put the camera back
>>> again. During climbing one of the high peaks, you are struggling to get
>>> breath and avoid fall, thought of taking an artistic picture does not
>>> come
>>> to mind. Once the camera is out, it will function for 10-20 minutes,
>>> depending on the ambient temperature & more importantly the wind chill
>>> factor. Quite often when the actual temperature is -20C, wind chill
>>> factor
>>> would make it more like -70C. Focusing motor may function for a while
>>> but
>>> the lens barrel, being exposed directly to the elements, would freeze
>>> very
>>> quickly. Around the high peaks on a decent day the air is so clear &
>>> free
>>> of dust that very ordinary cameras can take excellent pictures. I doubt
>>> very much that cooling of the sensor has anything to do with it. By the
>>> time the sensor is cooling down to a noise-suppressing level, the
>>> rest of
>>> the camera, including its shutter mechanism would probably be frozen.
>>
>>
>>
>> I thought the wind chill factor only affected something coated in
>> water or something generating heat. Its the ability of air to conduct
>> heat away from the body and the gradient. The steeper the temp
>> difference the faster heat will transfer. As transference occurs the
>> medium (this case air) heats up, thus the temp differential is reduced
>> and thus thermal conductivity is reduced. The greater the air
>> movement basically means the more changes of air in a given space of
>> time. The other part of windchill is water evapouration. Water
>> evapourating draws energy. So now you have relative moisture levels
>> included that behave the same way as relative temperature levels.
>>
>> So where is all this going? Well consider this last fact, a fan isn't
>> moving "cool air" for the most part the air is the same temperature it
>> doesn't magically become cooler as it passes through a fan as such,
>> its evapouration of sweat. Water does not cool, evapourating water
>> does. So humid conditions tend to feel hotter as there is less
>> evapouration. Water is actually a good insulator, ask any wetsuit owner.
>>
>> "So what?" i hear you ask. Well the camera will remain at the ambient
>> temperature. It is not losing heat, it is not generating any to
>> lose. Nor does it sweat. Condensation freezing is the most likely
>> cause of a jammed auto focus. Then of course any lubricants. So
>> whatever the ambient temperature is that the the temp of the camera or
>> any other inanimate object. Windchill is irrelevant.
>>
> If that were true, then there would be no point in putting a fan in a
> freezer, would there? Of COURSE wind chill matters!
>
>
Wind chill will only get things cold faster as it provides a fresh
supply of cold air. So, over long period of time, wind chill has no
effect on objects.
Anonymous
May 24, 2005 7:31:54 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Paul Bielec wrote:

> Ron Hunter wrote:
>
>> ian lincoln wrote:
>>
>>> "Gautam Majumdar" <gmajumdar@XSPAMfreeuk.com> wrote in message
>>> news:2gAke.120360$Cq2.61723@fe2.news.blueyonder.co.uk...
>>>
>>>> On Tue, 24 May 2005 04:31:49 +0100, Colin D wrote:
>>>>
>>>>> So it appears that -20C is certainly not the limit for digital
>>>>> cameras.
>>>>>
>>>>
>>>> During high altitude climbing people don't hang the cameras around
>>>> their
>>>> neck. Usually they are kept in one of the inside pockets of the
>>>> down-suite
>>>> where it remains close to the body temperature. People will get their
>>>> camera out, get a few shots in quick succession and put the camera back
>>>> again. During climbing one of the high peaks, you are struggling to get
>>>> breath and avoid fall, thought of taking an artistic picture does
>>>> not come
>>>> to mind. Once the camera is out, it will function for 10-20 minutes,
>>>> depending on the ambient temperature & more importantly the wind chill
>>>> factor. Quite often when the actual temperature is -20C, wind chill
>>>> factor
>>>> would make it more like -70C. Focusing motor may function for a
>>>> while but
>>>> the lens barrel, being exposed directly to the elements, would
>>>> freeze very
>>>> quickly. Around the high peaks on a decent day the air is so clear &
>>>> free
>>>> of dust that very ordinary cameras can take excellent pictures. I doubt
>>>> very much that cooling of the sensor has anything to do with it. By the
>>>> time the sensor is cooling down to a noise-suppressing level, the
>>>> rest of
>>>> the camera, including its shutter mechanism would probably be frozen.
>>>
>>>
>>>
>>>
>>> I thought the wind chill factor only affected something coated in
>>> water or something generating heat. Its the ability of air to
>>> conduct heat away from the body and the gradient. The steeper the
>>> temp difference the faster heat will transfer. As transference
>>> occurs the medium (this case air) heats up, thus the temp
>>> differential is reduced and thus thermal conductivity is reduced.
>>> The greater the air movement basically means the more changes of air
>>> in a given space of time. The other part of windchill is water
>>> evapouration. Water evapourating draws energy. So now you have
>>> relative moisture levels included that behave the same way as
>>> relative temperature levels.
>>>
>>> So where is all this going? Well consider this last fact, a fan
>>> isn't moving "cool air" for the most part the air is the same
>>> temperature it doesn't magically become cooler as it passes through a
>>> fan as such, its evapouration of sweat. Water does not cool,
>>> evapourating water does. So humid conditions tend to feel hotter as
>>> there is less evapouration. Water is actually a good insulator, ask
>>> any wetsuit owner.
>>>
>>> "So what?" i hear you ask. Well the camera will remain at the
>>> ambient temperature. It is not losing heat, it is not generating any
>>> to lose. Nor does it sweat. Condensation freezing is the most
>>> likely cause of a jammed auto focus. Then of course any lubricants.
>>> So whatever the ambient temperature is that the the temp of the
>>> camera or any other inanimate object. Windchill is irrelevant.
>>>
>> If that were true, then there would be no point in putting a fan in a
>> freezer, would there? Of COURSE wind chill matters!
>>
>>
> Wind chill will only get things cold faster as it provides a fresh
> supply of cold air. So, over long period of time, wind chill has no
> effect on objects.

.... except for the effect of thermal shock.

A couple years ago while shooting:
http://www.photo.net/photodb/photo?photo_id=1231417&siz...
it was -17°C and very windy (25 - 30 kts) plus I was under the downwash
of the AS-350 doing a series of closeups.

The film transport (or film canister?) jammed at about frame 20 or so in
about 15 minutes, and I reverted to my backup camera. I had to unload
the film in the dark. Camera worked fine ever since.

OTOH, the same camera has been outside all day at -28°C without a hickup
through several rolls.

Cheers,
Alan




--
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-- e-meil: Remove FreeLunch.
Anonymous
May 24, 2005 11:28:53 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Ron Hunter <rphunter@charter.net> writes:

>If that were true, then there would be no point in putting a fan in a
>freezer, would there? Of COURSE wind chill matters!

Perhaps we need to distinguish between different types of wind chill.

Anything that isn't at ambient temperature already will be affected by
a wind chill effect of some sort. It will lose heat faster when there's
a wind than in still air, because the wind strips away the heated air
next to the object faster than simple convection in still air.

But the effect of the wind will be different for self-heated objects
(like people) than for things that have no heat source and are merely
above ambient temperature. It's also different for things that have
surface moisture to evaporate (again, people) than if no moisture is
present.

The "wind chill factor" reported by the weather office is an attempt to
calculate the effect of these things on the subjective perception of
cold felt by *people*. If the temperature is -10 but the wind chill
factor is -40, that says that in the current wind it *feels*
approximately like -40 in still air. This does *not* mean that a camera
outside in these conditions will cool down as fast as if the outside
temperature was -40. The human-oriented wind chill factor doesn't apply
if you're not human.

On the other hand, a camera outdoors will be affected by some wind chill
effect - it just needs a different table to calculate it than the human
wind chill factor.

Dave
Anonymous
May 24, 2005 11:42:52 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

> If that were true, then there would be no point in putting a fan in a
> freezer, would there? Of COURSE wind chill matters!

In that instance it is to ensure that the whole freezer has air at the same
temperature not just the air at the base of the freezer. Cold air sinks hot
air rises. Fan assisted ovens work the same way and are supposed to reduce
the need to turn your food so that it is cooked evenly. Pretty much why
most microwaves rotate. Even coverage. When you touch metal outdoors it is
not colder than the air. It is merely conducting heat away from you far
more efficiently. The metal will be the same as the ambient temperature.
If you are not generating heat, and are not wet wind chill is not a factor.
Anonymous
May 24, 2005 11:42:53 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

ian lincoln wrote:
>>If that were true, then there would be no point in putting a fan in a
>>freezer, would there? Of COURSE wind chill matters!
>
>
> In that instance it is to ensure that the whole freezer has air at the same
> temperature not just the air at the base of the freezer. Cold air sinks hot
> air rises. Fan assisted ovens work the same way and are supposed to reduce
> the need to turn your food so that it is cooked evenly. Pretty much why
> most microwaves rotate. Even coverage. When you touch metal outdoors it is
> not colder than the air. It is merely conducting heat away from you far
> more efficiently. The metal will be the same as the ambient temperature.
> If you are not generating heat, and are not wet wind chill is not a factor.
>
>
Wrong. There is some benefit as to the distribution of the air, but
that fast is that moving cold air cools faster than still, cold air
because a warm object warms the air near it, and that warm air tends to
move only slowly upward due to heat convection. Fan forced cooling (or
heating) markedly reduces the time needed to cool a warm object, or to
warm a cold one. Ever blow on your soup spoon?


--
Ron Hunter rphunter@charter.net
Anonymous
May 25, 2005 1:35:41 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"Paul Bielec" <no@spam.com> wrote in message
news:D 6vi5l$edb$3@dns3.cae.ca...
> So, over long period of time, wind chill has no effect on objects.

I beg to disagree here Paul, it all depends what object you're talking
about. A camera? Maybe! But if that object happens to be hanging between
your legs, WELL THEN.....

I'm sorry, I just couldn't help it. :p 

Juan
Anonymous
May 25, 2005 2:09:24 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"Dave Martindale" <davem@cs.ubc.ca> wrote in message
news:D 6vv9l$kke$1@mughi.cs.ubc.ca...
SNIP
> The "wind chill factor" reported by the weather office is an
> attempt to calculate the effect of these things on the
> subjective perception of cold felt by *people*.

Keywords being; subjective and perception.

SNIP
> On the other hand, a camera outdoors will be affected by
> some wind chill effect - it just needs a different table to
> calculate it than the human wind chill factor.

Indeed, although it will not cool down below wind temperature. The
lowest ambient temperature is the limit, heat exchange is just faster
in air flow (at moderate air speed (!) ).
I've been told that the Concorde "grew" something like up to 5-10
inches in length due to air resistance while in flight, causing the
need for frequent inspection for metal fatigue.

Bart
Anonymous
May 25, 2005 2:42:24 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"Ron Hunter" <rphunter@charter.net> wrote in message
news:KYLke.522$fe2.177@fe02.lga...
> ian lincoln wrote:
>>>If that were true, then there would be no point in putting a fan in a
>>>freezer, would there? Of COURSE wind chill matters!
>>
>>
>> In that instance it is to ensure that the whole freezer has air at the
>> same temperature not just the air at the base of the freezer. Cold air
>> sinks hot air rises. Fan assisted ovens work the same way and are
>> supposed to reduce the need to turn your food so that it is cooked
>> evenly. Pretty much why most microwaves rotate. Even coverage. When
>> you touch metal outdoors it is not colder than the air. It is merely
>> conducting heat away from you far more efficiently. The metal will be
>> the same as the ambient temperature. If you are not generating heat, and
>> are not wet wind chill is not a factor.
> Wrong. There is some benefit as to the distribution of the air, but that
> fast is that moving cold air cools faster than still, cold air because a
> warm object warms the air near it, and that warm air tends to move only
> slowly upward due to heat convection. Fan forced cooling (or heating)
> markedly reduces the time needed to cool a warm object, or to warm a cold
> one. Ever blow on your soup spoon?

yes as the soup is generating heat. It has stored energy that the frequent
air changes carry away more efficiently. When an object reaches the ambient
temperature it will cool no more. A metal pole will feel cold but it is not
colder than surrounding air. As for fan forced cooling or heating i made
that point myself. As other posters have said chill factor is subjective.
Anonymous
May 25, 2005 2:42:25 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

ian lincoln wrote:
> "Ron Hunter" <rphunter@charter.net> wrote in message
> news:KYLke.522$fe2.177@fe02.lga...
>
>>ian lincoln wrote:
>>
>>>>If that were true, then there would be no point in putting a fan in a
>>>>freezer, would there? Of COURSE wind chill matters!
>>>
>>>
>>>In that instance it is to ensure that the whole freezer has air at the
>>>same temperature not just the air at the base of the freezer. Cold air
>>>sinks hot air rises. Fan assisted ovens work the same way and are
>>>supposed to reduce the need to turn your food so that it is cooked
>>>evenly. Pretty much why most microwaves rotate. Even coverage. When
>>>you touch metal outdoors it is not colder than the air. It is merely
>>>conducting heat away from you far more efficiently. The metal will be
>>>the same as the ambient temperature. If you are not generating heat, and
>>>are not wet wind chill is not a factor.
>>
>>Wrong. There is some benefit as to the distribution of the air, but that
>>fast is that moving cold air cools faster than still, cold air because a
>>warm object warms the air near it, and that warm air tends to move only
>>slowly upward due to heat convection. Fan forced cooling (or heating)
>>markedly reduces the time needed to cool a warm object, or to warm a cold
>>one. Ever blow on your soup spoon?
>
>
> yes as the soup is generating heat. It has stored energy that the frequent
> air changes carry away more efficiently. When an object reaches the ambient
> temperature it will cool no more. A metal pole will feel cold but it is not
> colder than surrounding air. As for fan forced cooling or heating i made
> that point myself. As other posters have said chill factor is subjective.
>
>
The point is that moving air will cool (or heat) faster than still air,
so wind DOES matter.


--
Ron Hunter rphunter@charter.net
Anonymous
May 25, 2005 5:55:39 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

For most of the right gender that would be "objects"

For winter outdoor types they make underwear with nice windbreaker
protection



"Juan Aranda" <juanaranda@securenet.net> wrote in message
news:D 70ll4$1c3g$1@news.securenet.net...
>
> "Paul Bielec" <no@spam.com> wrote in message
> news:D 6vi5l$edb$3@dns3.cae.ca...
>> So, over long period of time, wind chill has no effect on objects.
>
> I beg to disagree here Paul, it all depends what object you're talking
> about. A camera? Maybe! But if that object happens to be hanging
> between your legs, WELL THEN.....
>
> I'm sorry, I just couldn't help it. :p 
>
> Juan
>
Anonymous
May 25, 2005 7:48:58 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"Bart van der Wolf" <bvdwolf@no.spam> writes:

>I've been told that the Concorde "grew" something like up to 5-10
>inches in length due to air resistance while in flight, causing the
>need for frequent inspection for metal fatigue.

Yes, and the speed limit for the Concorde is not set by the engines, or
control issues - it's set by the maximum temperature allowed for things
like the nose that get the hottest due to this.

The SR-71 Blackbird goes a lot faster than the Concorde, but it uses
lots of titanium in the skin and frame where the Concorde uses mostly
stainless steel in hot spots.

Dave
Anonymous
May 25, 2005 1:13:34 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

ian lincoln wrote:

> I thought the wind chill factor only affected something coated in water or
> something generating heat. Its the ability of air to conduct heat away from
> the body and the gradient.

Wind chill means cool something quicker. It doesn't matter if it is
something live or heat generating. It is used in weather reports to
give an idea of how cold one will feel.

http://observe.arc.nasa.gov/nasa/earth/wind_chill/chill...

Water on a body at almost any temperature (and without wind) will make
you feel cooler as it absorb heat for evaporation. Wind helps the
evaporation, and takes even more heat from you. (BTW: Wool is a very
good insulator when wet, whereas most other natural fibres become heat
conductors).

The original wind chill "model" is based on the cooling rate of water in
a moderately insulated vessel at various temperatures and wind speeds.
The model is not particuarly accurate at all with respect to how people
feel. It's generally good enough to get people to put on gloves and a
warm hat and a scarf or whatever more they might need.

A year or so ago the Canadian miltary developed a more accurate wind
chill model. I have no idea if the weather service has adopted it.

IAC, on a cold day, in a stiff wind, your camera will cool much quicker,
especially an all metal mody.

Cheers,
Alan


--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.
Anonymous
May 25, 2005 7:53:42 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

ian lincoln wrote:
>
> "Ron Hunter" <rphunter@charter.net> wrote in message
> news:KYLke.522$fe2.177@fe02.lga...
> > ian lincoln wrote:
> >>>If that were true, then there would be no point in putting a fan in a
> >>>freezer, would there? Of COURSE wind chill matters!
> >>
> >>
> >> In that instance it is to ensure that the whole freezer has air at the
> >> same temperature not just the air at the base of the freezer. Cold air
> >> sinks hot air rises. Fan assisted ovens work the same way and are
> >> supposed to reduce the need to turn your food so that it is cooked
> >> evenly. Pretty much why most microwaves rotate. Even coverage. When
> >> you touch metal outdoors it is not colder than the air. It is merely
> >> conducting heat away from you far more efficiently. The metal will be
> >> the same as the ambient temperature. If you are not generating heat, and
> >> are not wet wind chill is not a factor.
> > Wrong. There is some benefit as to the distribution of the air, but that
> > fast is that moving cold air cools faster than still, cold air because a
> > warm object warms the air near it, and that warm air tends to move only
> > slowly upward due to heat convection. Fan forced cooling (or heating)
> > markedly reduces the time needed to cool a warm object, or to warm a cold
> > one. Ever blow on your soup spoon?
>
> yes as the soup is generating heat. It has stored energy that the frequent
> air changes carry away more efficiently. When an object reaches the ambient
> temperature it will cool no more. A metal pole will feel cold but it is not
> colder than surrounding air. As for fan forced cooling or heating i made
> that point myself. As other posters have said chill factor is subjective.

Has anyone made the point that windchill, or air movement, will cool an
object faster than in still air, but the temperature will bottom out at
the wind or air temp. But in the case of soup (if you blow long
enough!) or a moist object, the final temperature will be *lower* than
ambient due to the latent heat of evaporation of the liquid. This is
why fast-evaporating liquids like isopropyl alcohol or methylated
spirits will feel very cold on your skin, and why dry ice can give you
frostbite.

Colin
Anonymous
May 25, 2005 7:53:43 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Colin D wrote:
>
> ian lincoln wrote:
>
>>"Ron Hunter" <rphunter@charter.net> wrote in message
>>news:KYLke.522$fe2.177@fe02.lga...
>>
>>>ian lincoln wrote:
>>>
>>>>>If that were true, then there would be no point in putting a fan in a
>>>>>freezer, would there? Of COURSE wind chill matters!
>>>>
>>>>
>>>>In that instance it is to ensure that the whole freezer has air at the
>>>>same temperature not just the air at the base of the freezer. Cold air
>>>>sinks hot air rises. Fan assisted ovens work the same way and are
>>>>supposed to reduce the need to turn your food so that it is cooked
>>>>evenly. Pretty much why most microwaves rotate. Even coverage. When
>>>>you touch metal outdoors it is not colder than the air. It is merely
>>>>conducting heat away from you far more efficiently. The metal will be
>>>>the same as the ambient temperature. If you are not generating heat, and
>>>>are not wet wind chill is not a factor.
>>>
>>>Wrong. There is some benefit as to the distribution of the air, but that
>>>fast is that moving cold air cools faster than still, cold air because a
>>>warm object warms the air near it, and that warm air tends to move only
>>>slowly upward due to heat convection. Fan forced cooling (or heating)
>>>markedly reduces the time needed to cool a warm object, or to warm a cold
>>>one. Ever blow on your soup spoon?
>>
>>yes as the soup is generating heat. It has stored energy that the frequent
>>air changes carry away more efficiently. When an object reaches the ambient
>>temperature it will cool no more. A metal pole will feel cold but it is not
>>colder than surrounding air. As for fan forced cooling or heating i made
>>that point myself. As other posters have said chill factor is subjective.
>
>
> Has anyone made the point that windchill, or air movement, will cool an
> object faster than in still air, but the temperature will bottom out at
> the wind or air temp. But in the case of soup (if you blow long
> enough!) or a moist object, the final temperature will be *lower* than
> ambient due to the latent heat of evaporation of the liquid. This is
> why fast-evaporating liquids like isopropyl alcohol or methylated
> spirits will feel very cold on your skin, and why dry ice can give you
> frostbite.
>
> Colin

Dry ice (CO2) is quite cold enough to damage skin tissue even if it
didn't extract head by sublimation.


--
Ron Hunter rphunter@charter.net
Anonymous
May 25, 2005 7:53:43 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"Colin D" <ColinD@killspam.127.0.0.1> wrote in message
news:4293F6C6.1A17B259@killspam.127.0.0.1...
>
>
> ian lincoln wrote:
>>
>> "Ron Hunter" <rphunter@charter.net> wrote in message
>> news:KYLke.522$fe2.177@fe02.lga...
>> > ian lincoln wrote:
>> >>>If that were true, then there would be no point in putting a fan in a
>> >>>freezer, would there? Of COURSE wind chill matters!
>> >>
>> >>
>> >> In that instance it is to ensure that the whole freezer has air at the
>> >> same temperature not just the air at the base of the freezer. Cold
>> >> air
>> >> sinks hot air rises. Fan assisted ovens work the same way and are
>> >> supposed to reduce the need to turn your food so that it is cooked
>> >> evenly. Pretty much why most microwaves rotate. Even coverage. When
>> >> you touch metal outdoors it is not colder than the air. It is merely
>> >> conducting heat away from you far more efficiently. The metal will be
>> >> the same as the ambient temperature. If you are not generating heat,
>> >> and
>> >> are not wet wind chill is not a factor.
>> > Wrong. There is some benefit as to the distribution of the air, but
>> > that
>> > fast is that moving cold air cools faster than still, cold air because
>> > a
>> > warm object warms the air near it, and that warm air tends to move only
>> > slowly upward due to heat convection. Fan forced cooling (or heating)
>> > markedly reduces the time needed to cool a warm object, or to warm a
>> > cold
>> > one. Ever blow on your soup spoon?
>>
>> yes as the soup is generating heat. It has stored energy that the
>> frequent
>> air changes carry away more efficiently. When an object reaches the
>> ambient
>> temperature it will cool no more. A metal pole will feel cold but it is
>> not
>> colder than surrounding air. As for fan forced cooling or heating i made
>> that point myself. As other posters have said chill factor is
>> subjective.
>
> Has anyone made the point that windchill, or air movement, will cool an
> object faster than in still air, but the temperature will bottom out at
> the wind or air temp.

Yes I have.
But in the case of soup (if you blow long
> enough!) or a moist object, the final temperature will be *lower* than
> ambient due to the latent heat of evaporation of the liquid.

No but i have pointed out as cameras don't sweat that isn't an issue.

This is
> why fast-evaporating liquids like isopropyl alcohol or methylated
> spirits will feel very cold on your skin, and why dry ice can give you
> frostbite.

Dry ice is usually super cooled. It is rapidly conducting the heat out of
your body faster than blood can carry more to that area.
Anonymous
May 25, 2005 11:03:43 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"Alan Browne" <alan.browne@FreeLunchVideotron.ca> wrote in message
news:_R_ke.68194$3R6.2855375@weber.videotron.net...
> ian lincoln wrote:
>
>> I thought the wind chill factor only affected something coated in water
>> or something generating heat. Its the ability of air to conduct heat
>> away from the body and the gradient.
>
> Wind chill means cool something quicker. It doesn't matter if it is
> something live or heat generating. It is used in weather reports to give
> an idea of how cold one will feel.
>
> http://observe.arc.nasa.gov/nasa/earth/wind_chill/chill...
>
> Water on a body at almost any temperature (and without wind) will make you
> feel cooler as it absorb heat for evaporation. Wind helps the
> evaporation, and takes even more heat from you. (BTW: Wool is a very good
> insulator when wet, whereas most other natural fibres become heat
> conductors).
>
> The original wind chill "model" is based on the cooling rate of water in a
> moderately insulated vessel at various temperatures and wind speeds. The
> model is not particuarly accurate at all with respect to how people feel.
> It's generally good enough to get people to put on gloves and a warm hat
> and a scarf or whatever more they might need.
>
> A year or so ago the Canadian miltary developed a more accurate wind chill
> model. I have no idea if the weather service has adopted it.
>
> IAC, on a cold day, in a stiff wind, your camera will cool much quicker,
> especially an all metal mody.

I don't have a problem with that.

This actually fits my model. still air ambient temperature= -40c.
Wind chill factor = equivalent still air ambient temperature-70 (as quoted
in OP).
This doesn't mean the wind is -70. As my other posts state it allows you to
cool things quicker as if you were in a -70 environment. The actual
temperature of the camera will be the ambient temperature. If the ambient
temperature is -40 then that is the temp it will drop to. It may drop
quicker than that with the air moving but it will not drop to -70.

AS i mentioned before the rate of temp change is actually governed by the
temperature difference. This is known as the gradient. some call this the
differential. If you plotted the temp drop on a graph of a beaker of water
and its temp dropping to the ambient temp you would get a steep curve to
begin with but as the temps become closer the temp drop diminishes. Now
circulating the air with a fan would improve the temp drop but the temp
would not drop below ambient temp.

Now if you repeat the experiment at a lower ambient temperature the temp
will drop faster. Keep lowering the ambient temp until the temp drop
matches that of circulating the air then. Lets say for this experiment the
first ambient temp was 20C. Now when you plot the temp drop of the fan
assisted cooling with the repeatedly lower ambient temps without circulating
you will finally get a matching graph. you now have calculated the wind
chill for that particular fan.

so now you have a plotted temperature drop down to the ambient temp. you
have your fan assisted temp drop and you have a lower than ambient temp
drop. Lets say for argument sake this required the ambient temp to be 15C
to match the rate of temperature drop of the 20C fan assisted drop. Then
your fan had a chill factor of 15C. However you will find the fan doesn't
drop the temp below the ambient temp 20C. The fast moving air in the
windchill factor is still only at -40C in the OP post so my assertion is
still that a dry camera will not drop below-40C the ambient temperature.
The slightly moist human fighting to retain a core temp of 37.5C will be far
more affected by the windchill of factor of -70C.

I do hope that finally clears up any misunderstandings by all.
Anonymous
May 25, 2005 11:03:44 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

ian lincoln wrote:

> I do hope that finally clears up any misunderstandings by all.


I don't think anyone implied [too lazy to go look at the OP] that wind
chill equals the final rest temperature, it just accelerates the cooling
_rate_ to faster than what a standalone difference in temperature will do.

With evaporation, you can very easilly go below ambient temperature.

When crossing the desert, travellers used to put a bladder of water on
the hood of the truck. The bladder would seep, and the evaporation
(acclerated by the airflow) would cool the water to well below ambient,
in some cases forming ice inside the bladder. Thus a cold glass of
water was available at regular stops.

Such is also the condition when ice forms in a carburator (remember
those?). Ice forms in a carburator very well up to +15C ambient at high
humidity, as the evaporating gasoline chills the air rapidly. The
Volkswagen Beetle V 1.0 was quite susceptible to this. Carburator
engined aircraft always require carb heat in some operating conditions,
injectioned aircraft much less so (they have a heated air bypass in case
induction icing, however).

Cheers,
Alan

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.
Anonymous
May 25, 2005 11:03:45 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Alan Browne wrote:
> ian lincoln wrote:
>
>> I do hope that finally clears up any misunderstandings by all.
>
>
>
> I don't think anyone implied [too lazy to go look at the OP] that wind
> chill equals the final rest temperature, it just accelerates the cooling
> _rate_ to faster than what a standalone difference in temperature will do.
>
> With evaporation, you can very easilly go below ambient temperature.
>
> When crossing the desert, travellers used to put a bladder of water on
> the hood of the truck. The bladder would seep, and the evaporation
> (acclerated by the airflow) would cool the water to well below ambient,
> in some cases forming ice inside the bladder. Thus a cold glass of
> water was available at regular stops.
>
> Such is also the condition when ice forms in a carburator (remember
> those?). Ice forms in a carburator very well up to +15C ambient at high
> humidity, as the evaporating gasoline chills the air rapidly. The
> Volkswagen Beetle V 1.0 was quite susceptible to this. Carburator
> engined aircraft always require carb heat in some operating conditions,
> injectioned aircraft much less so (they have a heated air bypass in case
> induction icing, however).
>
> Cheers,
> Alan
>
A friend back at university ended up crash landing her Cessna in a field
after the air intake froze. She said that she forgot to action a lever
that sends hot air at the intake to warm it up.
Anonymous
May 26, 2005 12:45:26 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"Colin D" <ColinD@killspam.127.0.0.1> wrote in message
news:4292A025.19B1EA40@killspam.127.0.0.1...
> Some time back there was a thread about using digital cameras below
> zero, and IIRC the consensus was that - 20C was about the limit, for
> batteries as well.
>
> Last night the local camera club invited a guest to show us his images
> of his 2004 Everest climb. He used a Sony (I think) compact, no model
> mentioned, but he chose it because it used AA batteries, and he took a
> supply of AA lithiums.
>
> Apart from the breathtaking scenery, projected with a high-end digital
> projector, the gradation and detail in the snow textures had me thinking
> at first that these were scanned film shots, but he assured us that they
> were digital images, beautifully - if automatically - exposed.
>
> He remarked that at the higher altitudes, it was all he could do to
> remember to take the shots, let alone think about exposures, and he
> mentioned several shots that he just didn't think to take, like himself
> on the summit.
>
> But, as the subject line mentions, he said the temperatures above 8,000
> metres were between -35C to -40C, and the camera continued to function,
> except that at the very coldest, the focusing froze, and some of the
> shots were out of focus.
>
> So it appears that -20C is certainly not the limit for digital cameras.
>
> Colin.

Interesting.
What I'd like to know is how he kept it warm via his body without seriously
fogging the lens, both externally and perhaps even internally. Unless he
kept it in some sort of insulated pocket that disallowed any moisture from
his body to enter, this would be a real problem. -And once a lens gets
fogged in that environment, it's nearly impossible to clear it--since you're
heavily gloved, etc.
-Mark
Anonymous
May 26, 2005 12:49:21 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Ron Hunter wrote:
>
> Colin D wrote:
> >
> > ian lincoln wrote:
> >
> >>"Ron Hunter" <rphunter@charter.net> wrote in message
> >>news:KYLke.522$fe2.177@fe02.lga...
> >>
> >>>ian lincoln wrote:
> >>>
> >>>>>If that were true, then there would be no point in putting a fan in a
> >>>>>freezer, would there? Of COURSE wind chill matters!
> >>>>
> >>>>
> >>>>In that instance it is to ensure that the whole freezer has air at the
> >>>>same temperature not just the air at the base of the freezer. Cold air
> >>>>sinks hot air rises. Fan assisted ovens work the same way and are
> >>>>supposed to reduce the need to turn your food so that it is cooked
> >>>>evenly. Pretty much why most microwaves rotate. Even coverage. When
> >>>>you touch metal outdoors it is not colder than the air. It is merely
> >>>>conducting heat away from you far more efficiently. The metal will be
> >>>>the same as the ambient temperature. If you are not generating heat, and
> >>>>are not wet wind chill is not a factor.
> >>>
> >>>Wrong. There is some benefit as to the distribution of the air, but that
> >>>fast is that moving cold air cools faster than still, cold air because a
> >>>warm object warms the air near it, and that warm air tends to move only
> >>>slowly upward due to heat convection. Fan forced cooling (or heating)
> >>>markedly reduces the time needed to cool a warm object, or to warm a cold
> >>>one. Ever blow on your soup spoon?
> >>
> >>yes as the soup is generating heat. It has stored energy that the frequent
> >>air changes carry away more efficiently. When an object reaches the ambient
> >>temperature it will cool no more. A metal pole will feel cold but it is not
> >>colder than surrounding air. As for fan forced cooling or heating i made
> >>that point myself. As other posters have said chill factor is subjective.
> >
> >
> > Has anyone made the point that windchill, or air movement, will cool an
> > object faster than in still air, but the temperature will bottom out at
> > the wind or air temp. But in the case of soup (if you blow long
> > enough!) or a moist object, the final temperature will be *lower* than
> > ambient due to the latent heat of evaporation of the liquid. This is
> > why fast-evaporating liquids like isopropyl alcohol or methylated
> > spirits will feel very cold on your skin, and why dry ice can give you
> > frostbite.
> >
> > Colin
>
> Dry ice (CO2) is quite cold enough to damage skin tissue even if it
> didn't extract head by sublimation.
>
> --
> Ron Hunter rphunter@charter.net

It only gets that way - cold - because of sublimation. Dry ice
contained in a fire extinguisher or CO2 'bomb' for carbonated drinks is
at ambient temperature.

Colin
Anonymous
May 26, 2005 12:49:22 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Colin D wrote:
>
> Ron Hunter wrote:
>
>>Colin D wrote:
>>
>>>ian lincoln wrote:
>>>
>>>
>>>>"Ron Hunter" <rphunter@charter.net> wrote in message
>>>>news:KYLke.522$fe2.177@fe02.lga...
>>>>
>>>>
>>>>>ian lincoln wrote:
>>>>>
>>>>>
>>>>>>>If that were true, then there would be no point in putting a fan in a
>>>>>>>freezer, would there? Of COURSE wind chill matters!
>>>>>>
>>>>>>
>>>>>>In that instance it is to ensure that the whole freezer has air at the
>>>>>>same temperature not just the air at the base of the freezer. Cold air
>>>>>>sinks hot air rises. Fan assisted ovens work the same way and are
>>>>>>supposed to reduce the need to turn your food so that it is cooked
>>>>>>evenly. Pretty much why most microwaves rotate. Even coverage. When
>>>>>>you touch metal outdoors it is not colder than the air. It is merely
>>>>>>conducting heat away from you far more efficiently. The metal will be
>>>>>>the same as the ambient temperature. If you are not generating heat, and
>>>>>>are not wet wind chill is not a factor.
>>>>>
>>>>>Wrong. There is some benefit as to the distribution of the air, but that
>>>>>fast is that moving cold air cools faster than still, cold air because a
>>>>>warm object warms the air near it, and that warm air tends to move only
>>>>>slowly upward due to heat convection. Fan forced cooling (or heating)
>>>>>markedly reduces the time needed to cool a warm object, or to warm a cold
>>>>>one. Ever blow on your soup spoon?
>>>>
>>>>yes as the soup is generating heat. It has stored energy that the frequent
>>>>air changes carry away more efficiently. When an object reaches the ambient
>>>>temperature it will cool no more. A metal pole will feel cold but it is not
>>>>colder than surrounding air. As for fan forced cooling or heating i made
>>>>that point myself. As other posters have said chill factor is subjective.
>>>
>>>
>>>Has anyone made the point that windchill, or air movement, will cool an
>>>object faster than in still air, but the temperature will bottom out at
>>>the wind or air temp. But in the case of soup (if you blow long
>>>enough!) or a moist object, the final temperature will be *lower* than
>>>ambient due to the latent heat of evaporation of the liquid. This is
>>>why fast-evaporating liquids like isopropyl alcohol or methylated
>>>spirits will feel very cold on your skin, and why dry ice can give you
>>>frostbite.
>>>
>>>Colin
>>
>>Dry ice (CO2) is quite cold enough to damage skin tissue even if it
>>didn't extract head by sublimation.
>>
>>--
>>Ron Hunter rphunter@charter.net
>
>
> It only gets that way - cold - because of sublimation. Dry ice
> contained in a fire extinguisher or CO2 'bomb' for carbonated drinks is
> at ambient temperature.
>
> Colin

Colin,
You CAN'T be that dense. CO2 in a solid form at STP is about 75
degrees F. below zero. Compressing itallows it to exist at room temp.

When the pressure is released, it expands, and adsorbs heat.


--
Ron Hunter rphunter@charter.net
Anonymous
May 26, 2005 12:52:28 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"ian lincoln" <jessops@sux.com> wrote in message
news:amFke.90417$a9.76717@fe3.news.blueyonder.co.uk...
>
> "Gautam Majumdar" <gmajumdar@XSPAMfreeuk.com> wrote in message
> news:2gAke.120360$Cq2.61723@fe2.news.blueyonder.co.uk...
>> On Tue, 24 May 2005 04:31:49 +0100, Colin D wrote:
>>>
>>> So it appears that -20C is certainly not the limit for digital cameras.
>>>
>> During high altitude climbing people don't hang the cameras around their
>> neck. Usually they are kept in one of the inside pockets of the
>> down-suite
>> where it remains close to the body temperature. People will get their
>> camera out, get a few shots in quick succession and put the camera back
>> again. During climbing one of the high peaks, you are struggling to get
>> breath and avoid fall, thought of taking an artistic picture does not
>> come
>> to mind. Once the camera is out, it will function for 10-20 minutes,
>> depending on the ambient temperature & more importantly the wind chill
>> factor. Quite often when the actual temperature is -20C, wind chill
>> factor
>> would make it more like -70C. Focusing motor may function for a while but
>> the lens barrel, being exposed directly to the elements, would freeze
>> very
>> quickly. Around the high peaks on a decent day the air is so clear & free
>> of dust that very ordinary cameras can take excellent pictures. I doubt
>> very much that cooling of the sensor has anything to do with it. By the
>> time the sensor is cooling down to a noise-suppressing level, the rest of
>> the camera, including its shutter mechanism would probably be frozen.
>
> I thought the wind chill factor only affected something coated in water or
> something generating heat. Its the ability of air to conduct heat away
> from the body and the gradient. The steeper the temp difference the
> faster heat will transfer. As transference occurs the medium (this case
> air) heats up, thus the temp differential is reduced and thus thermal
> conductivity is reduced. The greater the air movement basically means the
> more changes of air in a given space of time. The other part of windchill
> is water evapouration. Water evapourating draws energy. So now you have
> relative moisture levels included that behave the same way as relative
> temperature levels.
>
> So where is all this going? Well consider this last fact, a fan isn't
> moving "cool air" for the most part the air is the same temperature it
> doesn't magically become cooler as it passes through a fan as such, its
> evapouration of sweat. Water does not cool, evapourating water does. So
> humid conditions tend to feel hotter as there is less evapouration. Water
> is actually a good insulator, ask any wetsuit owner.
>
> "So what?" i hear you ask. Well the camera will remain at the ambient
> temperature. It is not losing heat, it is not generating any to lose.
> Nor does it sweat. Condensation freezing is the most likely cause of a
> jammed auto focus. Then of course any lubricants. So whatever the
> ambient temperature is that the the temp of the camera or any other
> inanimate object. Windchill is irrelevant.

There's more to wind-chill that just evaporation.
Still air allows the formation of temperature "zones" around objects, where
they tend to form a buffer, of sorts, of air that remains effected by the
objects temperature difference compared with ambient temps. I don't think
the argumen that the camera is already at the ambient temp (and therefore
stays teh same) holds water in this case, because if it were really -40C, it
wouldn't operate at all.
Anonymous
May 26, 2005 6:23:23 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

In rec.photo.digital Ron Hunter <rphunter@charter.net> wrote:
>Colin D wrote:
>> Some time back there was a thread about using digital cameras below
>> zero, and IIRC the consensus was that - 20C was about the limit, for
>> batteries as well.
>>
>> Last night the local camera club invited a guest to show us his images
>> of his 2004 Everest climb. He used a Sony (I think) compact, no model
>> mentioned, but he chose it because it used AA batteries, and he took a
>> supply of AA lithiums.
>>
>> Apart from the breathtaking scenery, projected with a high-end digital
>> projector, the gradation and detail in the snow textures had me thinking
>> at first that these were scanned film shots, but he assured us that they
>> were digital images, beautifully - if automatically - exposed.
>>
>> He remarked that at the higher altitudes, it was all he could do to
>> remember to take the shots, let alone think about exposures, and he
>> mentioned several shots that he just didn't think to take, like himself
>> on the summit.
>>
>> But, as the subject line mentions, he said the temperatures above 8,000
>> metres were between -35C to -40C, and the camera continued to function,
>> except that at the very coldest, the focusing froze, and some of the
>> shots were out of focus.
>>
>> So it appears that -20C is certainly not the limit for digital cameras.
>>
>> Colin.

>No, in fact, digital cameras work BETTER when they get cold as noise
>levels drop dramatically. The issues are the focusing mechanism, as you
>mentioned, and the batteries. If the batteries are kept warm, and
>focusing isn't a problem (a fixed focus camera might be better under
>such hostile conditions), then the digital camera will get BETTER
>pictures in cold conditions.

Digital cameras do NOT work better at temperatures below
freezing. The sensor might, but the rest doesn't.

My Canon 300D manual claims that one should not operate
the camera below 32F.

I have, of course. But there are well-known problems with
the focussing mechanism, the diaphram closure, and shutter
operation the colder the camera.

I know you know all this, but don't confuse newbies by
saying that the *camera* works better. It doesn't.

---- Paul J. Gans
Anonymous
May 26, 2005 6:30:32 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

In rec.photo.digital Ron Hunter <rphunter@charter.net> wrote:
>ian lincoln wrote:
>> "Gautam Majumdar" <gmajumdar@XSPAMfreeuk.com> wrote in message
>> news:2gAke.120360$Cq2.61723@fe2.news.blueyonder.co.uk...
>>
>>>On Tue, 24 May 2005 04:31:49 +0100, Colin D wrote:
>>>
>>>>So it appears that -20C is certainly not the limit for digital cameras.
>>>>
>>>
>>>During high altitude climbing people don't hang the cameras around their
>>>neck. Usually they are kept in one of the inside pockets of the down-suite
>>>where it remains close to the body temperature. People will get their
>>>camera out, get a few shots in quick succession and put the camera back
>>>again. During climbing one of the high peaks, you are struggling to get
>>>breath and avoid fall, thought of taking an artistic picture does not come
>>>to mind. Once the camera is out, it will function for 10-20 minutes,
>>>depending on the ambient temperature & more importantly the wind chill
>>>factor. Quite often when the actual temperature is -20C, wind chill factor
>>>would make it more like -70C. Focusing motor may function for a while but
>>>the lens barrel, being exposed directly to the elements, would freeze very
>>>quickly. Around the high peaks on a decent day the air is so clear & free
>>>of dust that very ordinary cameras can take excellent pictures. I doubt
>>>very much that cooling of the sensor has anything to do with it. By the
>>>time the sensor is cooling down to a noise-suppressing level, the rest of
>>>the camera, including its shutter mechanism would probably be frozen.
>>
>>
>> I thought the wind chill factor only affected something coated in water or
>> something generating heat. Its the ability of air to conduct heat away from
>> the body and the gradient. The steeper the temp difference the faster heat
>> will transfer. As transference occurs the medium (this case air) heats up,
>> thus the temp differential is reduced and thus thermal conductivity is
>> reduced. The greater the air movement basically means the more changes of
>> air in a given space of time. The other part of windchill is water
>> evapouration. Water evapourating draws energy. So now you have relative
>> moisture levels included that behave the same way as relative temperature
>> levels.
>>
>> So where is all this going? Well consider this last fact, a fan isn't
>> moving "cool air" for the most part the air is the same temperature it
>> doesn't magically become cooler as it passes through a fan as such, its
>> evapouration of sweat. Water does not cool, evapourating water does. So
>> humid conditions tend to feel hotter as there is less evapouration. Water
>> is actually a good insulator, ask any wetsuit owner.
>>
>> "So what?" i hear you ask. Well the camera will remain at the ambient
>> temperature. It is not losing heat, it is not generating any to lose. Nor
>> does it sweat. Condensation freezing is the most likely cause of a jammed
>> auto focus. Then of course any lubricants. So whatever the ambient
>> temperature is that the the temp of the camera or any other inanimate
>> object. Windchill is irrelevant.
>>
>>
>If that were true, then there would be no point in putting a fan in a
>freezer, would there? Of COURSE wind chill matters!

Good grief! You *are* kidding, aren't you?

Wind chill depends on water evaporation.

The fan in the freezer is to make sure that there are no
"dead spots" in the freezer. It doesn't run all the time
but just for a while when you open the freezer door. It
ensures that cold air is mixed with any warm that has crept
in.

---- Paul J. Gans
Anonymous
May 26, 2005 6:36:06 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

In rec.photo.digital Ron Hunter <rphunter@charter.net> wrote:
>ian lincoln wrote:
>> "Ron Hunter" <rphunter@charter.net> wrote in message
>> news:KYLke.522$fe2.177@fe02.lga...
>>
>>>ian lincoln wrote:
>>>
>>>>>If that were true, then there would be no point in putting a fan in a
>>>>>freezer, would there? Of COURSE wind chill matters!
>>>>
>>>>
>>>>In that instance it is to ensure that the whole freezer has air at the
>>>>same temperature not just the air at the base of the freezer. Cold air
>>>>sinks hot air rises. Fan assisted ovens work the same way and are
>>>>supposed to reduce the need to turn your food so that it is cooked
>>>>evenly. Pretty much why most microwaves rotate. Even coverage. When
>>>>you touch metal outdoors it is not colder than the air. It is merely
>>>>conducting heat away from you far more efficiently. The metal will be
>>>>the same as the ambient temperature. If you are not generating heat, and
>>>>are not wet wind chill is not a factor.
>>>
>>>Wrong. There is some benefit as to the distribution of the air, but that
>>>fast is that moving cold air cools faster than still, cold air because a
>>>warm object warms the air near it, and that warm air tends to move only
>>>slowly upward due to heat convection. Fan forced cooling (or heating)
>>>markedly reduces the time needed to cool a warm object, or to warm a cold
>>>one. Ever blow on your soup spoon?
>>
>>
>> yes as the soup is generating heat. It has stored energy that the frequent
>> air changes carry away more efficiently. When an object reaches the ambient
>> temperature it will cool no more. A metal pole will feel cold but it is not
>> colder than surrounding air. As for fan forced cooling or heating i made
>> that point myself. As other posters have said chill factor is subjective.
>>
>>
>The point is that moving air will cool (or heat) faster than still air,
>so wind DOES matter.

Not much on Everest. Or anyplace else at -40.

---- Paul J. Gans
Anonymous
May 26, 2005 2:14:37 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Paul J Gans wrote:

> Wind chill depends on water evaporation.

No. It does not "depend" on evaporation. Wind chill simply provides
for more heat removing capacity. Evaporation (if there is something to
evaporate) increases the rate of cooling further (see my other post).

Take a solid dry object and place it outdoors on a -10C day. It will
take some time to cool.
Same on a windy day, it will cool much quicker. (All this depends on
the internal heat capacity and resistance, surface area and smoothness.
Smooth objects cool more slowly than textured objects).

Your car radiator is a "wind chill" device (for which, if there is
insufficient cooling, the fan will turn on to increase the cooling. No
evaporation. Likewise computer fans.

Cheers,
Alan.

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.
Anonymous
May 26, 2005 2:21:03 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Paul J Gans wrote:

>>The point is that moving air will cool (or heat) faster than still air,
>>so wind DOES matter.
>
>
> Not much on Everest. Or anyplace else at -40.

More than enough. The air density at 30,000' is about 1/3 of sea level
density. And it is very windy. So a wind of 30 KTS (Calm for Everst)
would be as much cooling capacity as 10 KTS at sea level. At -40, that
would chill a person to hypothermia in minutes if not properly dressed.

A few hundred miles north of here, -40 is a regular occurance in winter,
at near sea level ... and people seem content to live and work there...

Cheers,
Alan

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.
Anonymous
May 26, 2005 2:47:47 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Ron Hunter wrote:
>
> Colin D wrote:
> >
> > Ron Hunter wrote:
> >
>
> >>>Has anyone made the point that windchill, or air movement, will cool an
> >>>object faster than in still air, but the temperature will bottom out at
> >>>the wind or air temp. But in the case of soup (if you blow long
> >>>enough!) or a moist object, the final temperature will be *lower* than
> >>>ambient due to the latent heat of evaporation of the liquid. This is
> >>>why fast-evaporating liquids like isopropyl alcohol or methylated
> >>>spirits will feel very cold on your skin, and why dry ice can give you
> >>>frostbite.
> >>>
> >>>Colin
> >>
> >>Dry ice (CO2) is quite cold enough to damage skin tissue even if it
> >>didn't extract head by sublimation.
> >>
> >>--
> >>Ron Hunter rphunter@charter.net
> >
> >
> > It only gets that way - cold - because of sublimation. Dry ice
> > contained in a fire extinguisher or CO2 'bomb' for carbonated drinks is
> > at ambient temperature.
> >
> > Colin
>
> Colin,
> You CAN'T be that dense. CO2 in a solid form at STP is about 75
> degrees F. below zero. Compressing itallows it to exist at room temp.
>
> When the pressure is released, it expands, and adsorbs heat.

I have no argument with that, except the 'dense' part {:-)

To amplify what I said, CO2 in solid form at STP is continuously
sublimating, that's what lowers its temp to about -75F (your figure). I
normally work in Celcius, and the boiling/sublimation point of CO2 at
STP is -79C, which is -110F, so the temperature of a block of dry ice at
STP will approach that value. So a piece of dry ice that has been
sublimating will give you frostbite. It's already cold because the heat
required to cause sublimation is being extracted from itself.

On the other hand, when it's contained in a gastight enclosure, it
cannot sublimate past the point where the internal pressure equals its
vapour pressure, therefore no sublimation, no heat extraction. Otherwise
CO2 fire extinguishers would be very cold, which they aren't.

Colin
Anonymous
May 26, 2005 3:26:32 PM

Archived from groups: rec.photo.digital (More info?)

On Thu, 26 May 2005 10:14:37 -0400, Alan Browne wrote:

>> Wind chill depends on water evaporation.
>
> No. It does not "depend" on evaporation. Wind chill simply provides
> for more heat removing capacity. Evaporation (if there is something to
> evaporate) increases the rate of cooling further (see my other post).

I think you're both right, but you're talking about two different
"wind chill"s. Yours is the chilling effect (or it could be the
warming effect with different temperatures) as air passes over an
object, which doesn't require evaporation. There's also a specific
way for "wind chill" measurements to be made that does utilize the
evaporation of water. The way measurements are made was modified
several years ago, but I believe that it it still utilizes the
evaporation of water.
Anonymous
May 26, 2005 7:56:36 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"Mark²" wrote:
>
> "Colin D" <ColinD@killspam.127.0.0.1> wrote in message
> news:4292A025.19B1EA40@killspam.127.0.0.1...
> > Some time back there was a thread about using digital cameras below
> > zero, and IIRC the consensus was that - 20C was about the limit, for
> > batteries as well.
> >
> > Last night the local camera club invited a guest to show us his images
> > of his 2004 Everest climb. He used a Sony (I think) compact, no model
> > mentioned, but he chose it because it used AA batteries, and he took a
> > supply of AA lithiums.
> >
> > Apart from the breathtaking scenery, projected with a high-end digital
> > projector, the gradation and detail in the snow textures had me thinking
> > at first that these were scanned film shots, but he assured us that they
> > were digital images, beautifully - if automatically - exposed.
> >
> > He remarked that at the higher altitudes, it was all he could do to
> > remember to take the shots, let alone think about exposures, and he
> > mentioned several shots that he just didn't think to take, like himself
> > on the summit.
> >
> > But, as the subject line mentions, he said the temperatures above 8,000
> > metres were between -35C to -40C, and the camera continued to function,
> > except that at the very coldest, the focusing froze, and some of the
> > shots were out of focus.
> >
> > So it appears that -20C is certainly not the limit for digital cameras.
> >
> > Colin.
>
> Interesting.
> What I'd like to know is how he kept it warm via his body without seriously
> fogging the lens, both externally and perhaps even internally. Unless he
> kept it in some sort of insulated pocket that disallowed any moisture from
> his body to enter, this would be a real problem. -And once a lens gets
> fogged in that environment, it's nearly impossible to clear it--since you're
> heavily gloved, etc.
> -Mark

He mentioned that the humidity was/is zero at that height, and at Camp
III I think, it snows overnight, and when the sun comes up the snow
sublimates directly to water vapour - no liquid water forms.

So, I guess no humidity, no fogging - unless you breathe on it!

Colin
Anonymous
May 26, 2005 7:56:37 PM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

"Colin D" <ColinD@killspam.127.0.0.1> wrote in message
news:429548F4.A48BB91C@killspam.127.0.0.1...
>
>
> "Mark²" wrote:
>>
>> "Colin D" <ColinD@killspam.127.0.0.1> wrote in message
>> news:4292A025.19B1EA40@killspam.127.0.0.1...
>> > Some time back there was a thread about using digital cameras below
>> > zero, and IIRC the consensus was that - 20C was about the limit, for
>> > batteries as well.
>> >
>> > Last night the local camera club invited a guest to show us his images
>> > of his 2004 Everest climb. He used a Sony (I think) compact, no model
>> > mentioned, but he chose it because it used AA batteries, and he took a
>> > supply of AA lithiums.
>> >
>> > Apart from the breathtaking scenery, projected with a high-end digital
>> > projector, the gradation and detail in the snow textures had me
>> > thinking
>> > at first that these were scanned film shots, but he assured us that
>> > they
>> > were digital images, beautifully - if automatically - exposed.
>> >
>> > He remarked that at the higher altitudes, it was all he could do to
>> > remember to take the shots, let alone think about exposures, and he
>> > mentioned several shots that he just didn't think to take, like himself
>> > on the summit.
>> >
>> > But, as the subject line mentions, he said the temperatures above 8,000
>> > metres were between -35C to -40C, and the camera continued to function,
>> > except that at the very coldest, the focusing froze, and some of the
>> > shots were out of focus.
>> >
>> > So it appears that -20C is certainly not the limit for digital cameras.
>> >
>> > Colin.
>>
>> Interesting.
>> What I'd like to know is how he kept it warm via his body without
>> seriously
>> fogging the lens, both externally and perhaps even internally. Unless he
>> kept it in some sort of insulated pocket that disallowed any moisture
>> from
>> his body to enter, this would be a real problem. -And once a lens gets
>> fogged in that environment, it's nearly impossible to clear it--since
>> you're
>> heavily gloved, etc.
>> -Mark
>
> He mentioned that the humidity was/is zero at that height, and at Camp
> III I think, it snows overnight, and when the sun comes up the snow
> sublimates directly to water vapour - no liquid water forms.
>
> So, I guess no humidity, no fogging - unless you breathe on it!

I know humidity is low in the air...but inside your jacket it is VERY high
due to your body's perspiration, etc.
-Then as soon as you take that humidified camera OUT...the moisture from
your body quickly freezes onto, or fogs the lens--perhaps even internally.
Anonymous
May 27, 2005 12:47:48 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Colin D wrote:
>
> Ron Hunter wrote:
>
>>Colin D wrote:
>>
>>>Ron Hunter wrote:
>>>
>>
>>>>>Has anyone made the point that windchill, or air movement, will cool an
>>>>>object faster than in still air, but the temperature will bottom out at
>>>>>the wind or air temp. But in the case of soup (if you blow long
>>>>>enough!) or a moist object, the final temperature will be *lower* than
>>>>>ambient due to the latent heat of evaporation of the liquid. This is
>>>>>why fast-evaporating liquids like isopropyl alcohol or methylated
>>>>>spirits will feel very cold on your skin, and why dry ice can give you
>>>>>frostbite.
>>>>>
>>>>>Colin
>>>>
>>>>Dry ice (CO2) is quite cold enough to damage skin tissue even if it
>>>>didn't extract head by sublimation.
>>>>
>>>>--
>>>>Ron Hunter rphunter@charter.net
>>>
>>>
>>>It only gets that way - cold - because of sublimation. Dry ice
>>>contained in a fire extinguisher or CO2 'bomb' for carbonated drinks is
>>>at ambient temperature.
>>>
>>>Colin
>>
>>Colin,
>> You CAN'T be that dense. CO2 in a solid form at STP is about 75
>>degrees F. below zero. Compressing itallows it to exist at room temp.
>>
>>When the pressure is released, it expands, and adsorbs heat.
>
>
> I have no argument with that, except the 'dense' part {:-)
>
> To amplify what I said, CO2 in solid form at STP is continuously
> sublimating, that's what lowers its temp to about -75F (your figure). I
> normally work in Celcius, and the boiling/sublimation point of CO2 at
> STP is -79C, which is -110F, so the temperature of a block of dry ice at
> STP will approach that value. So a piece of dry ice that has been
> sublimating will give you frostbite. It's already cold because the heat
> required to cause sublimation is being extracted from itself.
>
> On the other hand, when it's contained in a gastight enclosure, it
> cannot sublimate past the point where the internal pressure equals its
> vapour pressure, therefore no sublimation, no heat extraction. Otherwise
> CO2 fire extinguishers would be very cold, which they aren't.
>
> Colin
Not until you begin to release CO2, then the container becomes quite cold.

--
Ron Hunter rphunter@charter.net
Anonymous
May 27, 2005 12:48:27 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Paul J Gans wrote:
> In rec.photo.digital Ron Hunter <rphunter@charter.net> wrote:
>
>>Colin D wrote:
>>
>>>Some time back there was a thread about using digital cameras below
>>>zero, and IIRC the consensus was that - 20C was about the limit, for
>>>batteries as well.
>>>
>>>Last night the local camera club invited a guest to show us his images
>>>of his 2004 Everest climb. He used a Sony (I think) compact, no model
>>>mentioned, but he chose it because it used AA batteries, and he took a
>>>supply of AA lithiums.
>>>
>>>Apart from the breathtaking scenery, projected with a high-end digital
>>>projector, the gradation and detail in the snow textures had me thinking
>>>at first that these were scanned film shots, but he assured us that they
>>>were digital images, beautifully - if automatically - exposed.
>>>
>>>He remarked that at the higher altitudes, it was all he could do to
>>>remember to take the shots, let alone think about exposures, and he
>>>mentioned several shots that he just didn't think to take, like himself
>>>on the summit.
>>>
>>>But, as the subject line mentions, he said the temperatures above 8,000
>>>metres were between -35C to -40C, and the camera continued to function,
>>>except that at the very coldest, the focusing froze, and some of the
>>>shots were out of focus.
>>>
>>>So it appears that -20C is certainly not the limit for digital cameras.
>>>
>>>Colin.
>
>
>>No, in fact, digital cameras work BETTER when they get cold as noise
>>levels drop dramatically. The issues are the focusing mechanism, as you
>>mentioned, and the batteries. If the batteries are kept warm, and
>>focusing isn't a problem (a fixed focus camera might be better under
>>such hostile conditions), then the digital camera will get BETTER
>>pictures in cold conditions.
>
>
> Digital cameras do NOT work better at temperatures below
> freezing. The sensor might, but the rest doesn't.
>
> My Canon 300D manual claims that one should not operate
> the camera below 32F.
>
> I have, of course. But there are well-known problems with
> the focussing mechanism, the diaphram closure, and shutter
> operation the colder the camera.
>
> I know you know all this, but don't confuse newbies by
> saying that the *camera* works better. It doesn't.
>
> ---- Paul J. Gans

Moving parts may cause problems, but the electronics is MUCH happier.


--
Ron Hunter rphunter@charter.net
Anonymous
May 27, 2005 12:50:32 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Paul J Gans wrote:
> In rec.photo.digital Ron Hunter <rphunter@charter.net> wrote:
>
>>ian lincoln wrote:
>>
>>>"Gautam Majumdar" <gmajumdar@XSPAMfreeuk.com> wrote in message
>>>news:2gAke.120360$Cq2.61723@fe2.news.blueyonder.co.uk...
>>>
>>>
>>>>On Tue, 24 May 2005 04:31:49 +0100, Colin D wrote:
>>>>
>>>>
>>>>>So it appears that -20C is certainly not the limit for digital cameras.
>>>>>
>>>>
>>>>During high altitude climbing people don't hang the cameras around their
>>>>neck. Usually they are kept in one of the inside pockets of the down-suite
>>>>where it remains close to the body temperature. People will get their
>>>>camera out, get a few shots in quick succession and put the camera back
>>>>again. During climbing one of the high peaks, you are struggling to get
>>>>breath and avoid fall, thought of taking an artistic picture does not come
>>>>to mind. Once the camera is out, it will function for 10-20 minutes,
>>>>depending on the ambient temperature & more importantly the wind chill
>>>>factor. Quite often when the actual temperature is -20C, wind chill factor
>>>>would make it more like -70C. Focusing motor may function for a while but
>>>>the lens barrel, being exposed directly to the elements, would freeze very
>>>>quickly. Around the high peaks on a decent day the air is so clear & free
>>>>of dust that very ordinary cameras can take excellent pictures. I doubt
>>>>very much that cooling of the sensor has anything to do with it. By the
>>>>time the sensor is cooling down to a noise-suppressing level, the rest of
>>>>the camera, including its shutter mechanism would probably be frozen.
>>>
>>>
>>>I thought the wind chill factor only affected something coated in water or
>>>something generating heat. Its the ability of air to conduct heat away from
>>>the body and the gradient. The steeper the temp difference the faster heat
>>>will transfer. As transference occurs the medium (this case air) heats up,
>>>thus the temp differential is reduced and thus thermal conductivity is
>>>reduced. The greater the air movement basically means the more changes of
>>>air in a given space of time. The other part of windchill is water
>>>evapouration. Water evapourating draws energy. So now you have relative
>>>moisture levels included that behave the same way as relative temperature
>>>levels.
>>>
>>>So where is all this going? Well consider this last fact, a fan isn't
>>>moving "cool air" for the most part the air is the same temperature it
>>>doesn't magically become cooler as it passes through a fan as such, its
>>>evapouration of sweat. Water does not cool, evapourating water does. So
>>>humid conditions tend to feel hotter as there is less evapouration. Water
>>>is actually a good insulator, ask any wetsuit owner.
>>>
>>>"So what?" i hear you ask. Well the camera will remain at the ambient
>>>temperature. It is not losing heat, it is not generating any to lose. Nor
>>>does it sweat. Condensation freezing is the most likely cause of a jammed
>>>auto focus. Then of course any lubricants. So whatever the ambient
>>>temperature is that the the temp of the camera or any other inanimate
>>>object. Windchill is irrelevant.
>>>
>>>
>>
>>If that were true, then there would be no point in putting a fan in a
>>freezer, would there? Of COURSE wind chill matters!
>
>
> Good grief! You *are* kidding, aren't you?
>
> Wind chill depends on water evaporation.
>
> The fan in the freezer is to make sure that there are no
> "dead spots" in the freezer. It doesn't run all the time
> but just for a while when you open the freezer door. It
> ensures that cold air is mixed with any warm that has crept
> in.
>
> ---- Paul J. Gans
The fan runs because moving air cools more rapidly. And, yes it does
move the warm air across the cooling fins, cooling it. How fast do you
think it would cool if it were just allowed to sit on the top of the
freezer compartment...?


--
Ron Hunter rphunter@charter.net
Anonymous
May 27, 2005 12:54:43 AM

Archived from groups: rec.photo.equipment.35mm,rec.photo.digital (More info?)

Mark² wrote:
> "Colin D" <ColinD@killspam.127.0.0.1> wrote in message
> news:4292A025.19B1EA40@killspam.127.0.0.1...
>
>>Some time back there was a thread about using digital cameras below
>>zero, and IIRC the consensus was that - 20C was about the limit, for
>>batteries as well.
>>
>>Last night the local camera club invited a guest to show us his images
>>of his 2004 Everest climb. He used a Sony (I think) compact, no model
>>mentioned, but he chose it because it used AA batteries, and he took a
>>supply of AA lithiums.
>>
>>Apart from the breathtaking scenery, projected with a high-end digital
>>projector, the gradation and detail in the snow textures had me thinking
>>at first that these were scanned film shots, but he assured us that they
>>were digital images, beautifully - if automatically - exposed.
>>
>>He remarked that at the higher altitudes, it was all he could do to
>>remember to take the shots, let alone think about exposures, and he
>>mentioned several shots that he just didn't think to take, like himself
>>on the summit.
>>
>>But, as the subject line mentions, he said the temperatures above 8,000
>>metres were between -35C to -40C, and the camera continued to function,
>>except that at the very coldest, the focusing froze, and some of the
>>shots were out of focus.
>>
>>So it appears that -20C is certainly not the limit for digital cameras.
>>
>>Colin.
>
>
> Interesting.
> What I'd like to know is how he kept it warm via his body without seriously
> fogging the lens, both externally and perhaps even internally. Unless he
> kept it in some sort of insulated pocket that disallowed any moisture from
> his body to enter, this would be a real problem. -And once a lens gets
> fogged in that environment, it's nearly impossible to clear it--since you're
> heavily gloved, etc.
> -Mark
>
>
That is a problem, but I suspect those who routinely deal with such cold
temps have solutions, such as silica gel.


--
Ron Hunter rphunter@charter.net
Anonymous
May 27, 2005 2:16:01 AM

Archived from groups: rec.photo.digital (More info?)

On Thu, 26 May 2005 20:48:27 -0500, Ron Hunter wrote:

> Moving parts may cause problems, but the electronics is MUCH happier.

Which category would you put the EVF and LCD displays in? I have
a hunch that at 40 below they'd make you completely forget about
shutter lag. :) 
Anonymous
May 27, 2005 3:10:15 AM

Archived from groups: rec.photo.digital (More info?)

On Thu, 26 May 2005 20:48:27 -0500, Ron Hunter <rphunter@charter.net>
wrote:


>Moving parts may cause problems, but the electronics is MUCH happier.


Not the battery, though. And look out when
that cold camera comes back into the warmth,
that's when things (especially the electronics)
might get very unhappy.

BTW, you're wrong about wind chill in one regard;
the concept is intended to describe the effects
of cold + wind on humans, not inanimate objects.

Look it up in Wikipedia. Here's the first sentence:

"Wind chill is the apparent temperature felt on the
exposed human (or animal) body due to the combination
of air temperature and wind speed."

Later in the same article:

"Wind chill also affects animals, and wet, inanimate
objects, but different formulae apply to them."

From britannica.com, wind chill is

"a measure of the rate of heat loss
from skin that is exposed to the air."


rafe b.
http://www.terrapinphoto.com
Anonymous
May 27, 2005 3:43:45 AM

Archived from groups: rec.photo.digital (More info?)

On Thu, 26 May 2005 22:16:01 -0400, ASAAR <caught@22.com> wrote:

>On Thu, 26 May 2005 20:48:27 -0500, Ron Hunter wrote:
>
>> Moving parts may cause problems, but the electronics is MUCH happier.
>
> Which category would you put the EVF and LCD displays in? I have
>a hunch that at 40 below they'd make you completely forget about
>shutter lag. :) 


Good point, I forgot about the LCD.

I remember skiing in Maine last winter,
on a particularly cold day. At lunch
I remembered that my PDA and my Canon
G2 were still in the car.

Fortunately there was no permanent
damage to either one, but neither
was usable in that condition.


rafe b.
http://www.terrapinphoto.com
Anonymous
May 27, 2005 6:54:28 AM

Archived from groups: rec.photo.digital (More info?)

ASAAR wrote:
> On Thu, 26 May 2005 20:48:27 -0500, Ron Hunter wrote:
>
>
>>Moving parts may cause problems, but the electronics is MUCH happier.
>
>
> Which category would you put the EVF and LCD displays in? I have
> a hunch that at 40 below they'd make you completely forget about
> shutter lag. :) 
>
LCDs are a special problem at low and high temps. I don't like EVFs, at
all. I would prefer a good optical viewfinder. Certainly for use in
extremes of temperature, LCD/EVF is a problem. I suspect one
anticipating use in temp extremes would choose some other type of
viewfinder as the LCD display need not be turned on.


--
Ron Hunter rphunter@charter.net
!