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DSLR "ISO"

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Anonymous
February 7, 2005 6:49:29 AM

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

I'm confused.

I understand what the ISO number means when it comes to film, but what
about a digital sensor? Is it just a change in electronic brightness
"gain"? If so, can I assume there is more "noise" associated with the
higher numbers? If I choose a higher number will I have gained
anything over processing the photo with image editing software later?

Let me ask it another way: I assume that if you choose a higher number
you'll get a shorter shutter speed and/or wider aperture for a given
amount of light, but since the physical sensor is the same what has
actually changed?

A related question:

In general terms how well do entry-level DSLRs do in low light
compared with film? If I "choose" ISO 800 do I end up with roughly the
same shutter/aperture combination that I would get with 800 speed
film? How is the "noise"?

What about long exposures? Reciprocity failure notwithstanding, I've
gotten some of my nicer travel shots at night with exposures of 5
seconds or more on film. How does a DSLR compare?

I am of course asking for "general case" answers. I assume different
models have different characteristics.

Greg Guarino

More about : dslr iso

Anonymous
February 7, 2005 6:49:30 AM

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

Greg G wrote:
>
> I'm confused.
>
> I understand what the ISO number means when it comes to film, but what
> about a digital sensor? Is it just a change in electronic brightness
> "gain"? If so, can I assume there is more "noise" associated with the
> higher numbers? If I choose a higher number will I have gained
> anything over processing the photo with image editing software later?
>
> Let me ask it another way: I assume that if you choose a higher number
> you'll get a shorter shutter speed and/or wider aperture for a given
> amount of light, but since the physical sensor is the same what has
> actually changed?
>
> A related question:
>
> In general terms how well do entry-level DSLRs do in low light
> compared with film? If I "choose" ISO 800 do I end up with roughly the
> same shutter/aperture combination that I would get with 800 speed
> film? How is the "noise"?

your light meter reads light for either film or digital.
iso 800 is iso 800.

>
> What about long exposures? Reciprocity failure notwithstanding, I've
> gotten some of my nicer travel shots at night with exposures of 5
> seconds or more on film. How does a DSLR compare?
>
> I am of course asking for "general case" answers. I assume different
> models have different characteristics.
>
> Greg Guarino
Anonymous
February 7, 2005 6:49:30 AM

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

"Greg G" <gdguarino@verizon.net> wrote in message
news:5fod01t780v12sklq4migrokmpamufv4mq@4ax.com...
> I'm confused.
>
> I understand what the ISO number means when it comes to film, but what
> about a digital sensor? Is it just a change in electronic brightness
> "gain"? If so, can I assume there is more "noise" associated with the
> higher numbers? If I choose a higher number will I have gained
> anything over processing the photo with image editing software later?
>
> Let me ask it another way: I assume that if you choose a higher number
> you'll get a shorter shutter speed and/or wider aperture for a given
> amount of light, but since the physical sensor is the same what has
> actually changed?
>
> A related question:
>
> In general terms how well do entry-level DSLRs do in low light
> compared with film? If I "choose" ISO 800 do I end up with roughly the
> same shutter/aperture combination that I would get with 800 speed
> film? How is the "noise"?
>
> What about long exposures? Reciprocity failure notwithstanding, I've
> gotten some of my nicer travel shots at night with exposures of 5
> seconds or more on film. How does a DSLR compare?
>
> I am of course asking for "general case" answers. I assume different
> models have different characteristics.
>
> Greg Guarino

ISO is ISO, the sensitivity of the sensor at any given ISO is equivalent to
the sensitivity of film at the same ISO.
Noise from digital tends to be less than grain from the same ISO film,
however.
Entry level cameras are fairly good in low light, depending on what you mean
by "low light." And they're better now than the midrange ones were just a
couple of years ago.
Digital will certainly get you good shots at shutters speeds as long or
longer than you went with film.
--
Skip Middleton
http://www.shadowcatcherimagery.com
Related resources
Anonymous
February 7, 2005 6:49:30 AM

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

Greg G commented courteously ...

> Let me ask it another way: I assume that if you
> choose a higher number you'll get a shorter shutter
> speed and/or wider aperture for a given amount of light,

Yes. But its higher shutter or *smaller* aperture, or some
combination of both, since each controls steps of 1/2 the
light coming into the "focal plane" - i.e., the sensors.

> but since the physical sensor is the same what has
> actually changed?
[snip]

Short answer with my limited knowledge, it's called
"signal amplification". The sensors don't get any more
sensitive but you can boost the signal to do more with a
given amount of photons or lumens (whichever you like).
All other factors being equal, but they seldom are, more
boost - i.e., higher digital ISO - the more noise.

OK, everyone, fair game on Jerry for being a twit! <grin>

--
ATM, aka Jerry
Anonymous
February 7, 2005 6:49:31 AM

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

Skip M commented courteously ...

> ISO is ISO,the sensitivity of the sensor at any given
> ISO is equivalent to the sensitivity of film at the
> same ISO.

By definition of ISO, right? Right.

> Noise from digital tends to be less than grain
> from the same ISO film, however. Entry level cameras are
> fairly good in low light, depending on what you mean by
> "low light." And they're better now than the midrange
> ones were just a couple of years ago. Digital will
> certainly get you good shots at shutters speeds as
> long or longer than you went with film.

I don't have nearly enough modern-day film or digital
experience to dispute you, and I'm not. But I'm usually
suspicious of blanket statements that "noise fromdigital
tends to be less than grain from the same ISO film".

I'll make my assertion as a question: aren't there
sometimes significant differences from one film
manufacturer to another at any given ISO? And, aren't
there sometimes significant differences when moving
between ISO ranges even within the same film manufacturer?

And, for digital, doesn't noise as well as image quality
have quite a bit to do with the quality of the sensors (as
measured by their cost), as well as if you always want to
be at the bleeding mega pixel edge, you're going to suffer
the most noise until a given manufacturer "catches up" and
builds "quieter" sensors? I didn't expect my wife's $150
Kodak to be as noise free, nor have as good image quality
as my $700 (retail) Nikon 5700 (of course, the 5700 also
has superior features).

--
ATM, aka Jerry
Anonymous
February 7, 2005 6:49:32 AM

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

"All Things Mopar" <usenetMAPS123@comcast.net> wrote in message
news:Xns95F634E4EA8EReplyToken@216.196.97.131...
> Skip M commented courteously ...
>
>> ISO is ISO,the sensitivity of the sensor at any given
>> ISO is equivalent to the sensitivity of film at the
>> same ISO.
>
> By definition of ISO, right? Right.
>
>> Noise from digital tends to be less than grain
>> from the same ISO film, however. Entry level cameras are
>> fairly good in low light, depending on what you mean by
>> "low light." And they're better now than the midrange
>> ones were just a couple of years ago. Digital will
>> certainly get you good shots at shutters speeds as
>> long or longer than you went with film.
>
> I don't have nearly enough modern-day film or digital
> experience to dispute you, and I'm not. But I'm usually
> suspicious of blanket statements that "noise fromdigital
> tends to be less than grain from the same ISO film".

That's why I said "tends" not the narrower "is." Earlier digitals, like the
D30, had very high levels of noise at high ISOs, especially 1600, much
higher than, say, Ilford Delta 3200.
>
> I'll make my assertion as a question: aren't there
> sometimes significant differences from one film
> manufacturer to another at any given ISO? And, aren't
> there sometimes significant differences when moving
> between ISO ranges even within the same film manufacturer?

Yes, there are, again why I tried to avoid using dogmatic phraseology.
>
> And, for digital, doesn't noise as well as image quality
> have quite a bit to do with the quality of the sensors (as
> measured by their cost), as well as if you always want to
> be at the bleeding mega pixel edge, you're going to suffer
> the most noise until a given manufacturer "catches up" and
> builds "quieter" sensors? I didn't expect my wife's $150
> Kodak to be as noise free, nor have as good image quality
> as my $700 (retail) Nikon 5700 (of course, the 5700 also
> has superior features).
Yes, but. The Canon 16mp 1Ds mkII has a pretty low level of noise, probably
one reason is costs so much. And the OP was asking about DSLRs, which
eliminates much discussion of noise vs. sensor dimensions, since, with the
exception of the Olympus 4/3 system, sensors range between APS and 35mm
size, and most of the sensors are of comparable quality.
>
> --
> ATM, aka Jerry

--
Skip Middleton
http://www.shadowcatcherimagery.com
Anonymous
February 7, 2005 2:37:44 PM

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

Greg G wrote:
> I'm confused.
>
> I understand what the ISO number means when it comes to film, but what
> about a digital sensor?

There is a discussion about this very topic over on rec.photo.digital

It seems that either the definition or the concept is not appropriate for
digital cameras because the image quality isn't taken into account. I can
have a point-and-shoot camera and a DLSR both work at ISO 800, but the
image quality will likely be much better from the DLSR.

If you take image quality into account, then you could perhaps say that a
point-and-shoot has a usable sensitivity of ISO 50 - 200, but that the
DSLR has a sensitivity up to ISO 1600, for example. Alternatively I guess
you could say that DSLRs at ISO 1600 were like ISO 200 film.

What I'm getting at is that although from the point of view of calculating
exposure ISO is useful, it doesn't reflect the image quality of different
cameras.

Cheers,
David
Anonymous
February 7, 2005 2:59:02 PM

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

On Mon, 07 Feb 2005 03:49:29 GMT, Greg G <gdguarino@verizon.net> wrote:

>I'm confused.
>
>I understand what the ISO number means when it comes to film, but what
>about a digital sensor? Is it just a change in electronic brightness
>"gain"? If so, can I assume there is more "noise" associated with the
>higher numbers? If I choose a higher number will I have gained
>anything over processing the photo with image editing software later?
>
>Let me ask it another way: I assume that if you choose a higher number
>you'll get a shorter shutter speed and/or wider aperture for a given
>amount of light, but since the physical sensor is the same what has
>actually changed?
>
>A related question:
>
>In general terms how well do entry-level DSLRs do in low light
>compared with film? If I "choose" ISO 800 do I end up with roughly the
>same shutter/aperture combination that I would get with 800 speed
>film? How is the "noise"?

Yes, it's electronic gain of the analogue sensor signals before they are
digitised. Yes, increasing ISO will increase noise: on small-sensored P&S
cameras, this can be a major problem, but for dSLRs, with physically larger
sensors, it's generally not too bad (and _generally_ better than high ISO
films).

The advantage of doing it in-camera with an ISO boost is that the gain
happens before digitisation. To illustrate the benefit, suppose the
(analogue) sensors generate from 0V (black) to 1V (light) and that this is
digitised to 0..100 (numbers are made up to make it easy to understand).

If you shoot a low-light shot with no ISO-boost, then the sensors might
only produce values between 0 and 0.1V, which will be digitised into pixel
values 0..10 (out of 100). If you post-process by scaling pixels by a
factor of 10, then while the brightest pixel will now be 100, you will ONLY
have pixels with values 0, 10, 20, ..., 80, 90, 100 -- there will be no
values "in between", so the image will show "banding".

If, however, you bump the ISO so that the analogue signal is boosted 10x,
then the 0 to 0.1V signal becomes a full-range 0 to 1.0V signal. When this
is digitised, you get a full-range 0..100 pixel range, with (potentially)
all shades in-between (plus some more noise).

>
>What about long exposures? Reciprocity failure notwithstanding, I've
>gotten some of my nicer travel shots at night with exposures of 5
>seconds or more on film. How does a DSLR compare?

Digital sensors don't suffer from the reciprocity failure that film does,
which makes long exposure shots easier to work with (as I understand; I've
never done this type of shot [yet]).

As well as "amplifier noise" (above, from high ISOs), digital sensors can
suffer from noise at long exposures. Many cameras will offer an option to
perform "dark frame subtraction" for long exposures (an equivalent length
"dark" shot is taken after the real shot and subtracted from the first).

>
>I am of course asking for "general case" answers. I assume different
>models have different characteristics.
>
>Greg Guarino


Regards,
Graham Holden (g-holden AT dircon DOT co DOT uk)
--
There are 10 types of people in the world;
those that understand binary and those that don't.
Anonymous
February 7, 2005 3:35:19 PM

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

Greg G wrote:

> I'm confused.

Enjoy it for a while.

>
> I understand what the ISO number means when it comes to film, but what
> about a digital sensor? Is it just a change in electronic brightness
> "gain"? If so, can I assume there is more "noise" associated with the
> higher numbers? If I choose a higher number will I have gained
> anything over processing the photo with image editing software later?

As others have replied, ISO is ISO.

However film and digital *are* different in many ways so a side by side will
have some differences.
Notably, as film ISO goes up, grain noise AND size increases.
Digital, only the noise increases. The pixels remain the same size.

>
> Let me ask it another way: I assume that if you choose a higher number
> you'll get a shorter shutter speed and/or wider aperture for a given
> amount of light, but since the physical sensor is the same what has
> actually changed?

Yep. Reciprocity rules as always. (you meant 'smaller' aperture above as IOS
rises, all other things being equal).

What changed? At lower ISO's (say up to 1600), the gain prior to digitization
is increased. Above that, simply shift the bits to the left (mult by 2) to get
3200, 6400... beginning at that point there is a drastic quantization noise
increase, however.... (better than no photo at all).

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: there's no such thing as a FreeLunch.
February 7, 2005 9:41:10 PM

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

On Mon, 07 Feb 2005 03:49:29 GMT, Greg G <gdguarino@verizon.net> wrote:

>I'm confused.

we all are... sometimes!

>I understand what the ISO number means when it comes to film, but what
>about a digital sensor? Is it just a change in electronic brightness
>"gain"?

That's it! Gain, just like any video signal in any amplifier.

> If so, can I assume there is more "noise" associated with the
>higher numbers?

Yes you can.

> If I choose a higher number will I have gained
>anything over processing the photo with image editing software later?

That's an interesting question! I'd say get as close as you can with the camera
first, since you may not be able to extract data in your software. It's like a
negative, you can go one way several stops over, but only about one stop the
wrong way, since there would be no emulsion left. Once you start 'clipping' the
electric image, there is no return. So stay towards the shadows where you can
recover. As to whether or not the camera or the external software is better -
I'd bet on the camera. But there are usually 'highlight' warnings on cameras,
so stay below that and fix the gamma in your external software.

>Let me ask it another way: I assume that if you choose a higher number
>you'll get a shorter shutter speed and/or wider aperture for a given
>amount of light, but since the physical sensor is the same what has
>actually changed?

The gain of the signal amplifier.

>A related question:
>
>In general terms how well do entry-level DSLRs do in low light
>compared with film? If I "choose" ISO 800 do I end up with roughly the
>same shutter/aperture combination that I would get with 800 speed
>film?

yes, that is how they calibrated the system. there is no such thing as ISO in a
sensor since it is amplified as a system. The 'ISO' number is just to let us
know what the camera would do if it were film.

Now I have a question - why no 'ISO 100" on the D70??

> How is the "noise"?

Going by my memory of when I shot film (decades ago I think...) I'd say I get
less noise with the digital. I remember shooting 400 color film and it being at
the edge of quality, but now I shoot at 800 all the time... and 1600 to get to
the edge.

Or course, different film and cameras - it depends!

>
>What about long exposures? Reciprocity failure notwithstanding, I've
>gotten some of my nicer travel shots at night with exposures of 5
>seconds or more on film. How does a DSLR compare?

It depends on the camera... I've seen long times that were great. Go to the
review site...

>I am of course asking for "general case" answers. I assume different
>models have different characteristics.

yup...

>Greg Guarino
Anonymous
February 7, 2005 9:44:12 PM

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

In article <36p289F53idhrU1@individual.net>,
David J Taylor <david-taylor@invalid.com> wrote:
>Greg G wrote:
>> I'm confused.
>>
>> I understand what the ISO number means when it comes to film, but what
>> about a digital sensor?
>
>There is a discussion about this very topic over on rec.photo.digital
>
>It seems that either the definition or the concept is not appropriate for
>digital cameras because the image quality isn't taken into account.

It wasn't taken into account on film cameras, either. Nor was sensor size.
If I put a sheet of slide film in a large-format camera, and a roll of the
same emulsion in a half-frame 35mm camera, I'd end up with a much better
quality image from the large-format. But, in each case, I'd need to set
the exposure based on the sensitivity of the film. That, and only that,
is what ISO measures.
Anonymous
February 8, 2005 2:19:21 AM

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

On Sun, 06 Feb 2005 23:13:42 -0600, All Things Mopar
<usenetMAPS123@comcast.net> wrote:

>Greg G commented courteously ...
>
>> Let me ask it another way: I assume that if you
>> choose a higher number you'll get a shorter shutter
>> speed and/or wider aperture for a given amount of light,
>
>Yes. But its higher shutter or *smaller* aperture, or some
>combination of both, since each controls steps of 1/2 the
>light coming into the "focal plane" - i.e., the sensors.

Of course. That's what happens when I don't proofread.

Greg
Anonymous
February 8, 2005 3:30:53 AM

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

In article <h3uf01df9a3nrlsk45bcpc0nah49j2gqhm@4ax.com>,
Bob <FlintsTone@Valve.Amps> wrote:
>On Mon, 07 Feb 2005 03:49:29 GMT, Greg G <gdguarino@verizon.net> wrote:
>
>>I'm confused.
>
>we all are... sometimes!

[ ... ]

>yes, that is how they calibrated the system. there is no such thing as ISO in a
>sensor since it is amplified as a system. The 'ISO' number is just to let us
>know what the camera would do if it were film.
>
>Now I have a question - why no 'ISO 100" on the D70??

At a guess, it is because the CCD saturates and starts
distorting or clipping the exposure curve with that much light.

And which came first -- ISO or ASA? I knew the ASA long before
I heard of ISO in film speeds. The only European film speed which I
knew back then was the DIN rating, which certainly did *not* match the
ASA of the time.

I would *really* like to have ASA/ISO 100 (or even down to ISO
50) for my old "Medical Nikkor" at the really close focal distances.
(Yes, it does work on the D70 with the flash sync adaptor module in the
shoe.)

Or -- I would like the necessary information to make a
"resistor" cord from the flash power supply to the head in the lens.

I'm rather reluctant to add a neutral density filter to the
(potential) stack of close-up lenses which are part of that system.
When using only a single close-up lens, I guess that I would be all
right, but some of the particularly close ones are a stack of two, and
the closest one has no secondary filter threads, so the filter would
have to be closer to the prime lens than at least one of the close-up
lenses.

As it is, I have gotten some interesting close-ups to a funnel
weaver spider (lion spider) who took up residence between the storm
window and the main window of our bathroom. s/he got enough to eat
because of the bugs which were attracted to the lights and got through
the crack left at the top of the storm window.

The spider has now passed on, and the webs are cleaned out. And,
the storm window is fully closed this time. :-)

Enjoy,
DoN.
--
Email: <dnichols@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
Anonymous
February 8, 2005 3:57:02 AM

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

"Greg G" <gdguarino@verizon.net> wrote in message
news:5fod01t780v12sklq4migrokmpamufv4mq@4ax.com...
> > snip stuff covvered well by others < <
> In general terms how well do entry-level DSLRs do in low light
> compared with film? If I "choose" ISO 800 do I end up with roughly the
> same shutter/aperture combination that I would get with 800 speed
> film? How is the "noise"?
>
> What about long exposures? Reciprocity failure notwithstanding, I've
> gotten some of my nicer travel shots at night with exposures of 5
> seconds or more on film. How does a DSLR compare?
>
> I am of course asking for "general case" answers. I assume different
> models have different characteristics.

Yes, long exposures are possible with all DSLRs currently on the new market.
Long has to be defined though. In general long is (for digitals anyway) 8
seconds to many minutes. And they can all do that to some degree.

If you are looking at doing up to about 30 seconds or so don't worry about
it, pick the one you like for other reasons, because they are all pretty
much OK to this point, some slightly better than others. If you want times
of over 5 minutes shutter then you need to look at each one on a case by
case basis. I think the current long exposure champ is probably the Canon
20D.

Here is a 10 minute Canon 20D exposure, at 400 ISO. The originator of the
this shot claims it is right out of the camera, and was originally shot as a
small fine jpg.
http://www.pbase.com/token/image/39340025/original.jpg

C
February 8, 2005 12:49:35 PM

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

Graham Holden wrote:
>
> The advantage of doing it in-camera with an ISO boost is that the gain
> happens before digitisation. To illustrate the benefit, suppose the
> (analogue) sensors generate from 0V (black) to 1V (light) and that this is
> digitised to 0..100 (numbers are made up to make it easy to understand).
>
> If you shoot a low-light shot with no ISO-boost, then the sensors might
> only produce values between 0 and 0.1V, which will be digitised into pixel
> values 0..10 (out of 100). If you post-process by scaling pixels by a
> factor of 10, then while the brightest pixel will now be 100, you will ONLY
> have pixels with values 0, 10, 20, ..., 80, 90, 100 -- there will be no
> values "in between", so the image will show "banding".
>
> If, however, you bump the ISO so that the analogue signal is boosted 10x,
> then the 0 to 0.1V signal becomes a full-range 0 to 1.0V signal. When this
> is digitised, you get a full-range 0..100 pixel range, with (potentially)
> all shades in-between (plus some more noise).


Thanks for this excellent explanation. If I follow correctly, the way to
check this is to get a 'full' looking histogram in the original capture
rather than brighten it up later.

On a somewhat related note; does anyone know if the exposure adjustment
in PS CS RAW plugin amounts to a real change in exposure or more like
any other software brightness control?
Anonymous
February 8, 2005 9:54:17 PM

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

Graham Holden <look@bottom.of.post> wrote:
> On Mon, 07 Feb 2005 03:49:29 GMT, Greg G <gdguarino@verizon.net> wrote:


> The advantage of doing it in-camera with an ISO boost is that the gain
> happens before digitisation. To illustrate the benefit, suppose the
> (analogue) sensors generate from 0V (black) to 1V (light) and that this is
> digitised to 0..100 (numbers are made up to make it easy to understand).

> If you shoot a low-light shot with no ISO-boost, then the sensors might
> only produce values between 0 and 0.1V, which will be digitised into pixel
> values 0..10 (out of 100).

It's even worse. Eyes are logarithmic (and so is jpeg), but
the sensor are linear. Assuming you can record 5 steps of
brightness (zone 3 to 7 inclusive), zone 7 would be 0.5-1V,
zone 6 0.25-0.5V, zone 5 0.125-0.25V, zone 4 0.0625-0.125V and
zone 3 0.03125-0.0625V. (and not much discernible below)

Which would not be a problem, but for the fact that the sensor
will record 0.03125V as 3, not as 3.125 ... There currently is
no commercial viable way to make the sensor record 1..10000 for
making up for the low voltage differences.

> If you post-process by scaling pixels by a
> factor of 10, then while the brightest pixel will now be 100, you will ONLY
> have pixels with values 0, 10, 20, ..., 80, 90, 100 -- there will be no
> values "in between", so the image will show "banding".

And that mostly in the darker part, not evenly distributed,
i.e. even more noticable.

> If, however, you bump the ISO so that the analogue signal is boosted 10x,
> then the 0 to 0.1V signal becomes a full-range 0 to 1.0V signal. When this
> is digitised, you get a full-range 0..100 pixel range, with (potentially)
> all shades in-between (plus some more noise).

.... thus bringing the sensor into a favourable working point,
where it can use it's whole resolution on the problem.

-Wolfgang
Anonymous
February 8, 2005 10:19:41 PM

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

DoN. Nichols <dnichols@d-and-d.com> wrote:

> And which came first -- ISO or ASA? I knew the ASA long before
> I heard of ISO in film speeds. The only European film speed which I
> knew back then was the DIN rating, which certainly did *not* match the
> ASA of the time.

DIN (Deutsche (German) Industrie Norm) is something you'll find
in many places, e.g. DIN A4 (paper size).
I assume the American Standards Association is similar in intent
as an organisation.

Pertaining to film:

DIN ASA ISO
15° 25 25/15°
18° 50 50/18°
21° 100 100/21°
24° 200 200/24°
27° 400 400/27°
30° 800 800/30°
33° 1600 1600/33°

So in DIN +1 is 1/3rd of a step.

-Wolfgang
Anonymous
February 8, 2005 10:19:42 PM

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

In article <tecnd2-fll.ln1@ID-52418.user.berlin.de>,
Wolfgang Weisselberg <ozcvgtt02@sneakemail.com> wrote:
>DoN. Nichols <dnichols@d-and-d.com> wrote:
>
>> And which came first -- ISO or ASA? I knew the ASA long before
>> I heard of ISO in film speeds. The only European film speed which I
>> knew back then was the DIN rating, which certainly did *not* match the
>> ASA of the time.
>
>DIN (Deutsche (German) Industrie Norm) is something you'll find
>in many places, e.g. DIN A4 (paper size).

I understand this, and am familiar with many DIN standards
(mostly from the fields of electronics and metalworking). And I realize
that many other exist of which I have no knowledge.

But I was in particular speaking of the standards for film
sensitivity. I grew up with ASA, and encountered DIN with certain
imported films, such as Isopan Record.

And I was then away from photography for many years, because I
worked for a US Government organization in which a security clearance
was necessary, and cameras were totally forbidden (even one just stored
in my car), so my standard practice of carrying at least one camera and
two lenses (50mm f1.4 and 135mm f3.5) was not possible, and photography
fell into disuse.

Now, I am retired. I still have too much to do to spend the
hours in the darkroom which I used to do, but the Digital cameras deal
with that quite nicely.

But -- when I came back to photography, I discovered that ASA
film speeds had been replaced with ISO film speeds, with apparently
identical values (for familiar films such as Tri-X and Ektrachrome, the
two which I used most often.)

>I assume the American Standards Association is similar in intent
>as an organisation.

Certainly. As is the ISO, which I know from computer language
standards and the such.

>Pertaining to film:
>
> DIN ASA ISO
> 15° 25 25/15°
> 18° 50 50/18°
> 21° 100 100/21°
> 24° 200 200/24°
> 27° 400 400/27°
> 30° 800 800/30°
> 33° 1600 1600/33°
>
>So in DIN +1 is 1/3rd of a step.

That table would save me a bit of looking up, if I still used
film instead of digital focal planes.

Thanks,
DoN.

--
Email: <dnichols@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
Anonymous
February 11, 2005 8:31:51 AM

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

Skip M wrote:

> Yes, there are, again why I tried to avoid using dogmatic phraseology.

oh, the irony...<g>







mike
!