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to UV or not to UV?

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Anonymous
January 11, 2005 9:07:54 PM

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

I have always had a UV filter on my lenses. It was always with the mind set
of protecting the front element. I have read different points of view on
this and many believe you degrade the optical quality by placing such a
filter on. I guess it might make a difference if you buy a cheap filter or a
multi-coated type? I have never scratched one of my UV filters so I guess my
front element would be pretty safe without a filter in place. If you have
quality glass (i.e. Canon L or Nikkor) are you defeating your good glass by
putting a UV filter in front? I'm just curious what other 'photoheads'
think.

thanks...mitch

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Anonymous
January 11, 2005 9:42:35 PM

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

Mitch wrote:
> I have always had a UV filter on my lenses. It was always with the mind set
> of protecting the front element. I have read different points of view on
> this and many believe you degrade the optical quality by placing such a
> filter on. I guess it might make a difference if you buy a cheap filter or a
> multi-coated type? I have never scratched one of my UV filters so I guess my
> front element would be pretty safe without a filter in place. If you have
> quality glass (i.e. Canon L or Nikkor) are you defeating your good glass by
> putting a UV filter in front? I'm just curious what other 'photoheads'
> think.
>
> thanks...mitch
>
>

are you defeating your good glass by putting a UV filter in front?

No, in my opinion. I use Hoya super coated UV filters
on all my lenses (except 500 mm f/4), including large
format lenses. I have found the need to use
the top anti-reflection coated filters, as many modern
lenses have a pretty flat front lens element. This results
in a reflection off of filters with more reflective coatings.
This becomes most obvious if you photograph the moon in twilight,
or lightning, or similar high intensity objects on a dark
background. Other than the reflection, a good quality filter
will not degrade quality. I did purchase a circular
polarizer filter once and the glass was not parallel.
It produced soft images and I returned it.

I find filters get dirty in the harsh environments
I work in (the outdoors), and after a few years I throw
them away and put on new ones after a number of cleanings.

Roger
Photos at: http://www.clarkvision.com
Anonymous
January 12, 2005 9:31:37 AM

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

I also use hood and put UV on only when on small boats, at the beach or
shooting snow shots.

Jim


*----------------------------------------------------------------*
* Check out my website at: http://SwensonStudio.com *
* travel and landscape photography featuring beautiful sunsets *
*----------------------------------------------------------------*

Joseph Meehan wrote:
> Mitch wrote:
> > I have always had a UV filter on my lenses. It was always with the
> > mind set of protecting the front element. I have read different
> > points of view on this and many believe you degrade the optical
> > quality by placing such a filter on. I guess it might make a
> > difference if you buy a cheap filter or a multi-coated type? I have
> > never scratched one of my UV filters so I guess my front element
> > would be pretty safe without a filter in place. If you have quality
> > glass (i.e. Canon L or Nikkor) are you defeating your good glass by
> > putting a UV filter in front? I'm just curious what other
> > 'photoheads' think.
> > thanks...mitch
>
> I believe you are on the right path. While it is true that a
filter may
> help protect a lens, for most of us that is a rather small need. It
is
> unlikely that most of us will ever damage a lens. I have not damaged
one in
> over 40 years. Of course I have been doing photography for more than
40
> years.
>
> Most lens damage is not material and can be further reduced by
the
> application of a little black ink in the scratch.
>
> Lens hoods offer better protection IMO.
>
> If you are going to be in an area that is likely to damage you
camera, I
> suggest using such a filter. (area like a windy beach or an
industrial
> area.)
>
> In short, life is far too short to worry about it either way.
>
> --
> Joseph Meehan
>
> 26 + 6 = 1 It's Irish Math
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Anonymous
January 12, 2005 1:47:26 PM

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

Roger:
Have you found that digital sensors are as sensitive to UV light as film?
i..e. do digital images have that bluish cast in higher altitudes?
thanks....MTB

"Roger N. Clark (change username to rnclark)" <username@qwest.net> wrote in
message news:41E4808B.7050600@qwest.net...
> Mitch wrote:
> > I have always had a UV filter on my lenses. It was always with the mind
set
> > of protecting the front element. I have read different points of view on
> > this and many believe you degrade the optical quality by placing such a
> > filter on. I guess it might make a difference if you buy a cheap filter
or a
> > multi-coated type? I have never scratched one of my UV filters so I
guess my
> > front element would be pretty safe without a filter in place. If you
have
> > quality glass (i.e. Canon L or Nikkor) are you defeating your good glass
by
> > putting a UV filter in front? I'm just curious what other 'photoheads'
> > think.
> >
> > thanks...mitch
> >
> >
>
> are you defeating your good glass by putting a UV filter in front?
>
> No, in my opinion. I use Hoya super coated UV filters
> on all my lenses (except 500 mm f/4), including large
> format lenses. I have found the need to use
> the top anti-reflection coated filters, as many modern
> lenses have a pretty flat front lens element. This results
> in a reflection off of filters with more reflective coatings.
> This becomes most obvious if you photograph the moon in twilight,
> or lightning, or similar high intensity objects on a dark
> background. Other than the reflection, a good quality filter
> will not degrade quality. I did purchase a circular
> polarizer filter once and the glass was not parallel.
> It produced soft images and I returned it.
>
> I find filters get dirty in the harsh environments
> I work in (the outdoors), and after a few years I throw
> them away and put on new ones after a number of cleanings.
>
> Roger
> Photos at: http://www.clarkvision.com
>
Anonymous
January 12, 2005 2:36:50 PM

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

Mitch wrote:
> I have always had a UV filter on my lenses. It was always with the
> mind set of protecting the front element. I have read different
> points of view on this and many believe you degrade the optical
> quality by placing such a filter on. I guess it might make a
> difference if you buy a cheap filter or a multi-coated type? I have
> never scratched one of my UV filters so I guess my front element
> would be pretty safe without a filter in place. If you have quality
> glass (i.e. Canon L or Nikkor) are you defeating your good glass by
> putting a UV filter in front? I'm just curious what other
> 'photoheads' think.
> thanks...mitch

I believe you are on the right path. While it is true that a filter may
help protect a lens, for most of us that is a rather small need. It is
unlikely that most of us will ever damage a lens. I have not damaged one in
over 40 years. Of course I have been doing photography for more than 40
years.

Most lens damage is not material and can be further reduced by the
application of a little black ink in the scratch.

Lens hoods offer better protection IMO.

If you are going to be in an area that is likely to damage you camera, I
suggest using such a filter. (area like a windy beach or an industrial
area.)

In short, life is far too short to worry about it either way.

--
Joseph Meehan

26 + 6 = 1 It's Irish Math
January 12, 2005 3:34:15 PM

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

Is a Quantaray DMC-UV a poor choice? I forget, I think it was about $20.
Anonymous
January 12, 2005 3:55:29 PM

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

On Tue, 11 Jan 2005 18:42:35 -0700, "Roger N. Clark (change
username to rnclark)" <username@qwest.net> wrote:

>Other than the reflection, a good quality filter
>will not degrade quality.

Roger,

the trouble is that the reflection is also there when you take
normal photos in, for example, diffuse daylight. The effect is
just not as conspicuous, but the stray light will reduce the
achievable contrast by lightening very dark areas.

In fact, the additional stray light from a filter overlays
everything in the picture, but its effect is most pronounced in
very dark areas.

I would not use a UV filter just for lens protection. The lens
is well enough protected by not protruding. When you mistreat
your camera enough to bang the front lens against hard objects,
it will probably break anyway, before you manage to break the
lens, but I think you shouldn't be a photographer then anyway.
(:-)

Hans-Georg

--
No mail, please.
Anonymous
January 12, 2005 3:55:30 PM

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

Hans-Georg Michna wrote:
> On Tue, 11 Jan 2005 18:42:35 -0700, "Roger N. Clark (change
> username to rnclark)" <username@qwest.net> wrote:
>
>
>>Other than the reflection, a good quality filter
>>will not degrade quality.
>
>
> Roger,
>
> the trouble is that the reflection is also there when you take
> normal photos in, for example, diffuse daylight. The effect is
> just not as conspicuous, but the stray light will reduce the
> achievable contrast by lightening very dark areas.

Yes, this is true, and that is why I use the hoya
super coated Hoya UV filters.

This page shows a test target with 10.6 stops of dynamic range,
and all images were taken with a Hoya UV filter on the lens:
http://clarkvision.com/imagedetail/dynamicrange2

This page shows an image with a dynamic range of 2300 to
one, over 10 stops, and there are no identifiable problems
from reflections from the filter.
http://clarkvision.com/imagedetail/dynamicrange

The fact that DSLR digital
cameras record a much higher dynamic range than film
and this urban legend about filters has been around before
DSLRs, indicates it is simply not an issue with a good filter.
After all, it is simply one piece of glass in lenses that
typically have 9 or more elements.

Roger
Anonymous
January 12, 2005 3:55:31 PM

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

Roger N. Clark (change username to rnclark) wrote:

> Hans-Georg Michna wrote:

>> the trouble is that the reflection is also there when you take
>> normal photos in, for example, diffuse daylight. The effect is
>> just not as conspicuous, but the stray light will reduce the
>> achievable contrast by lightening very dark areas.
>
>
> Yes, this is true, and that is why I use the hoya
> super coated Hoya UV filters.
>

Here is another stringent test: sunsets with the sun in
the frame: These images were all done with a Hoya UV filter:

http://clarkvision.com/galleries/gallery.NEW/web/hawaii...

http://clarkvision.com/galleries/gallery.NEW/web/hawaii...

http://clarkvision.com/galleries/gallery.NEW/web/hawaii...

I have seen no issues with reflections

Roger
Anonymous
January 12, 2005 3:55:31 PM

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

Roger:
Thanks for the links...took a quick look.
Could you clarify a few points for me..
1. when you refer to the dynamic range of film, are you referring to the
range captured on the negative or transparency, or to the range possible on
a custom print?
2. how does the dymanic range on a transparency viewed by transmitted
light..i.e. projected...compare to a digital image viewed on a PC monitor?
3. what would be the maximum dynamic range for a properly exposed print ?
Would the print be the limiting factor regardless of the source?
4. what would be the maximum dynamic range for a properly exposed TIFF image
on a calibrated PC monitor? Would the monitor be the limiting factor?
thanks again....MTB


"Roger N. Clark (change username to rnclark)" <username@qwest.net> wrote in
message news:41E539E2.1060108@qwest.net...
> Hans-Georg Michna wrote:
> > On Tue, 11 Jan 2005 18:42:35 -0700, "Roger N. Clark (change
> > username to rnclark)" <username@qwest.net> wrote:
> >
> >
> >>Other than the reflection, a good quality filter
> >>will not degrade quality.
> >
> >
> > Roger,
> >
> > the trouble is that the reflection is also there when you take
> > normal photos in, for example, diffuse daylight. The effect is
> > just not as conspicuous, but the stray light will reduce the
> > achievable contrast by lightening very dark areas.
>
> Yes, this is true, and that is why I use the hoya
> super coated Hoya UV filters.
>
> This page shows a test target with 10.6 stops of dynamic range,
> and all images were taken with a Hoya UV filter on the lens:
> http://clarkvision.com/imagedetail/dynamicrange2
>
> This page shows an image with a dynamic range of 2300 to
> one, over 10 stops, and there are no identifiable problems
> from reflections from the filter.
> http://clarkvision.com/imagedetail/dynamicrange
>
> The fact that DSLR digital
> cameras record a much higher dynamic range than film
> and this urban legend about filters has been around before
> DSLRs, indicates it is simply not an issue with a good filter.
> After all, it is simply one piece of glass in lenses that
> typically have 9 or more elements.
>
> Roger
>
Anonymous
January 12, 2005 9:50:49 PM

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

On Wed, 12 Jan 2005 10:59:06 -0500, "MTBike1970"
<NOSPAMmtbike1970@yahoo.ca> wrote:

>1. when you refer to the dynamic range of film, are you referring to the
>range captured on the negative or transparency, or to the range possible on
>a custom print?

Prints always have a low dynamic range, I think about 2 1/2
orders of magnitude, while film captures about 4. A good CMOS
sensor captures 6 orders of magnitude, quite a bit better than
CCD sensors.

>4. what would be the maximum dynamic range for a properly exposed TIFF image
>on a calibrated PC monitor? Would the monitor be the limiting factor?

In theory, a monitor in a darkened room can have an almost
limitless dynamic range, but in practice there is always some
residual light on the screen, and also a very large dynamic
range cannot be calibrated properly.

But anyway, monitors can have a fairly large dynamic range.

However, this holds only for electron beam tubes, not for LCD
monitors. Those have difficulties beyond 3 orders of magnitude.
I doubt that any of the current ones can reach 4.

Hans-Georg

--
No mail, please.
Anonymous
January 12, 2005 9:50:50 PM

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

On Wed, 12 Jan 2005 18:50:49 +0100, Hans-Georg Michna
<hans-georgNoEmailPlease@michna.com> wrote:

>On Wed, 12 Jan 2005 10:59:06 -0500, "MTBike1970"
><NOSPAMmtbike1970@yahoo.ca> wrote:
>
>>1. when you refer to the dynamic range of film, are you referring to the
>>range captured on the negative or transparency, or to the range possible on
>>a custom print?
>
>Prints always have a low dynamic range, I think about 2 1/2
>orders of magnitude, while film captures about 4. A good CMOS
>sensor captures 6 orders of magnitude, quite a bit better than
>CCD sensors.

...but at the cost of more noise:

http://www.dalsa.com/shared/content/OE_Magazine_Dueling...


--
Owamanga!
Anonymous
January 12, 2005 10:03:49 PM

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

MTBike1970 wrote:

> Roger:
> Have you found that digital sensors are as sensitive to UV light as film?
> i..e. do digital images have that bluish cast in higher altitudes?
> thanks....MTB

At higher elevation, the light is always bluer, regardless
of UV. So you do need to compensate. But this is
easy with digital (at least DSLRs). Now days, I
do not carry 81A or 81B filters with my digital cameras,
like I did with film.
I just change white balance, or shoot raw then adjust
white balance later.

Roger
Anonymous
January 12, 2005 11:16:33 PM

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

Hans-Georg Michna wrote:

> On Wed, 12 Jan 2005 10:59:06 -0500, "MTBike1970"
> <NOSPAMmtbike1970@yahoo.ca> wrote:
>
>
>>1. when you refer to the dynamic range of film, are you referring to the
>>range captured on the negative or transparency, or to the range possible on
>>a custom print?
>
>
> Prints always have a low dynamic range, I think about 2 1/2
> orders of magnitude,

2.5 orders of magnitude? 10^2.5 = 316. If the paper had
95% reflectance, and very dark ink (pure carbon lamp black
is ~1.5% reflectance, one gets (0.95-0.015)/0.015 = 62,
or 6 stops. More typical is maybe 5 stops. The 2.5 orders of
magnitude would require reflectance of 0.3%. I've never
seen such a material.

> while film captures about 4.

4 orders of magnitude, 10,000, is beyond even the wildest claims
I have ever heard. Commonly cited is 7 stops for print film,
and 5 stops for slide film. 7 stops = 2^7 = 128, 5 stops = 32.

On this page:
http://clarkvision.com/imagedetail/dynamicrange2
I show Kodak Gold 200 has about 7 stops (a consumer print film), and
Fujichrome Velvia has about 4 stops (a professional slide film)
of dynamic range.

> A good CMOS
> sensor captures 6 orders of magnitude, quite a bit better than
> CCD sensors.

If you read my pages already cited, and this page:
http://clarkvision.com/imagedetail/digital.signal.to.no...
you would see that DSLR sensors, including Nikon with CCDs
have over 10 stops. Typical full well capacities
are 45,000 to 52,00 electrons, with read noise
of 10 to 15 electrons. That works out to a max signal divided
read noise = dynamic range = 3,000 (11.5 stops) to 5200
(12.3 stops), thus limited by the 12-bit A to Ds.
These are current consumer and pro models working at
normal temperatures.

Look at figure 5 on this page:
http://clarkvision.com/imagedetail/dynamicrange2
where you can see the digital camera records much more than
the either print or slide film, over 10 stops in the one test
scene. Even the DSLR JPEG does that.

>>4. what would be the maximum dynamic range for a properly exposed TIFF image
>>on a calibrated PC monitor? Would the monitor be the limiting factor?
>
>
> In theory, a monitor in a darkened room can have an almost
> limitless dynamic range, but in practice there is always some
> residual light on the screen, and also a very large dynamic
> range cannot be calibrated properly.
>
> But anyway, monitors can have a fairly large dynamic range.
>
> However, this holds only for electron beam tubes, not for LCD
> monitors. Those have difficulties beyond 3 orders of magnitude.
> I doubt that any of the current ones can reach 4.

Take a look at LCD projectors, LCD TVs, and Plasma TVs.
They usually cite the contrast ratio in their specs.
You can probably find that for info for CRT now too.
I recall seeing 2000 to 4000 to one for plasma tvs.

Roger
Anonymous
January 12, 2005 11:55:27 PM

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

Hans-Georg Michna <hans-georgNoEmailPlease@michna.com> writes:

> I would not use a UV filter just for lens protection. The lens
> is well enough protected by not protruding. When you mistreat
> your camera enough to bang the front lens against hard objects,
> it will probably break anyway, before you manage to break the
> lens, but I think you shouldn't be a photographer then anyway.
> (:-)

People are generally more worried about scratch/gouge than they are
about break. I, on the other hand, had an unpleasant experience with
pineapple punch that made me quite glad there was a filter on the
front of my lens.

B>
Anonymous
January 12, 2005 11:55:28 PM

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

"Bruce Murphy" <pack-news@rattus.net> wrote in message
news:m2wtuiolhc.fsf@greybat.rattus.net...
> Hans-Georg Michna <hans-georgNoEmailPlease@michna.com> writes:
>
>> I would not use a UV filter just for lens protection. The lens
>> is well enough protected by not protruding. When you mistreat
>> your camera enough to bang the front lens against hard objects,
>> it will probably break anyway, before you manage to break the
>> lens, but I think you shouldn't be a photographer then anyway.
>> (:-)
>
> People are generally more worried about scratch/gouge than they are
> about break. I, on the other hand, had an unpleasant experience with
> pineapple punch that made me quite glad there was a filter on the
> front of my lens.
>
> B>

My camera is a tool to be used without worrying too much about getting it
moderately dirty. Salt spray at the beach during recent gales would be one
example. In such cases I prefer to be cleaning the dirt off the filter
rather than off the lens element. I can understand arguments for and
against the use of the UV filter as protection, but I prefer to keep the
filter on most of the time.

Dennis
Anonymous
January 13, 2005 7:59:03 AM

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

"Roger N. Clark (change username to rnclark)" <username@qwest.net> wrote:
>
> > while film captures about 4.
>
> 4 orders of magnitude, 10,000, is beyond even the wildest claims
> I have ever heard. Commonly cited is 7 stops for print film,
> and 5 stops for slide film. 7 stops = 2^7 = 128, 5 stops = 32.
>
> On this page:
> http://clarkvision.com/imagedetail/dynamicrange2
> I show Kodak Gold 200 has about 7 stops (a consumer print film), and
> Fujichrome Velvia has about 4 stops (a professional slide film)
> of dynamic range.

These numbers appear to be rather less than one would suppose
from looking at the manufacturers' H&D curves.

For instance Kodak Gold 200 -
www.kodak.com/global/images/en/consumer/products/techIn...

shows a log exposure range of at least 3.3 (11 stops) from the point
on the toe which shows at least 1/3 the average gamma up to the
point where they stop the curve where there is only the slightest
hint of a shoulder.

I'm puzzled how you only get seven stops exposure range. Even if
you insist on a minimum exposure a little further up the toe,
you should be getting at least 10 stops, not 7.

Peter.
--
pirwin@ktb.net
Anonymous
January 13, 2005 7:59:04 AM

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

Peter Irwin wrote:
> "Roger N. Clark (change username to rnclark)" <username@qwest.net> wrote:
>
>>> while film captures about 4.
>>
>>4 orders of magnitude, 10,000, is beyond even the wildest claims
>>I have ever heard. Commonly cited is 7 stops for print film,
>>and 5 stops for slide film. 7 stops = 2^7 = 128, 5 stops = 32.
>>
>>On this page:
>>http://clarkvision.com/imagedetail/dynamicrange2
>>I show Kodak Gold 200 has about 7 stops (a consumer print film), and
>>Fujichrome Velvia has about 4 stops (a professional slide film)
>>of dynamic range.
>
>
> These numbers appear to be rather less than one would suppose
> from looking at the manufacturers' H&D curves.
>
> For instance Kodak Gold 200 -
> www.kodak.com/global/images/en/consumer/products/techIn...
>
> shows a log exposure range of at least 3.3 (11 stops) from the point
> on the toe which shows at least 1/3 the average gamma up to the
> point where they stop the curve where there is only the slightest
> hint of a shoulder.
>
> I'm puzzled how you only get seven stops exposure range. Even if
> you insist on a minimum exposure a little further up the toe,
> you should be getting at least 10 stops, not 7.
>
> Peter.

Look again at each curve:
Blue: flattens out just under 1 (about .9) to a little over 3 (~3.2).
that is an OD range of ~3.2-.9 = 2.3. 10^2.3 = 200, ~7.6 stops.

green: OD ~ 0.7 to 2.6 = range of 1.9, 10^1.9 = 79 = 6.3 stops

red: OD ~0.2 to 2.0 = range of 1.8, 10^1.8 = 63, 6.0 stops.

My results are in line with Kodak's published data.

Roger
Anonymous
January 13, 2005 11:06:33 AM

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

There is a difference between blue light and UV. Silicon chips are not
very sensitive to true UV. However, even to the eye the atmosphere has
a blue haze over far objects. But there are several standard filters
that can eliminate this blue coloration, such as a minus blue filter or
skylight filter. The so-called UV filter very necessary for film has
minimal effect on most colors but cuts down on the shorter blue
wavelengths. No reasonably priced (absorption) filter has a real sharp
cutoff with color, so that is why the UV filter may be useful. It is
really just a weaker type of minus-blue or skylight. Skylight has less
effect on other colors than minus-blue, whose effect does extend down
into other colors. Minus blue is fully useful for black and white
photography, but may be too strong for color (though with color hue
editing potential for digital, I think it is probably more useful than
for color film. It makes the color quite "warm."
Anonymous
January 13, 2005 3:46:07 PM

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

Roger,

thanks for your interesting data! I'll work through it over the
next weekend and try to verify.

Hans-Georg

--
No mail, please.
Anonymous
January 13, 2005 3:46:09 PM

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

On Wed, 12 Jan 2005 19:03:49 -0700, "Roger N. Clark (change
username to rnclark)" <username@qwest.net> wrote:

>MTBike1970 wrote:

>> Have you found that digital sensors are as sensitive to UV light as film?
>> i..e. do digital images have that bluish cast in higher altitudes?
>> thanks....MTB

>At higher elevation, the light is always bluer, regardless
>of UV. So you do need to compensate. But this is
>easy with digital (at least DSLRs). Now days, I
>do not carry 81A or 81B filters with my digital cameras,
>like I did with film.
>I just change white balance, or shoot raw then adjust
>white balance later.

Roger,

when you actually get high UV levels, don't you need a UV filter
to keep the pictures sharp? Or do the lenses or sensors already
filter out UV light?

Hans-Georg

--
No mail, please.
Anonymous
January 13, 2005 3:46:10 PM

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

Hans-Georg Michna wrote:
> On Wed, 12 Jan 2005 19:03:49 -0700, "Roger N. Clark (change
> username to rnclark)" <username@qwest.net> wrote:
>
>
>>MTBike1970 wrote:
>
>
>>>Have you found that digital sensors are as sensitive to UV light as film?
>>>i..e. do digital images have that bluish cast in higher altitudes?
>>>thanks....MTB
>
>
>>At higher elevation, the light is always bluer, regardless
>>of UV. So you do need to compensate. But this is
>>easy with digital (at least DSLRs). Now days, I
>>do not carry 81A or 81B filters with my digital cameras,
>>like I did with film.
>>I just change white balance, or shoot raw then adjust
>>white balance later.
>
>
> Roger,
>
> when you actually get high UV levels, don't you need a UV filter
> to keep the pictures sharp? Or do the lenses or sensors already
> filter out UV light?
>
> Hans-Georg
>

That is a good question. I do not know the answer because
I always have on my UV filters, except on my 500mm f/4 lens.
The 500 does not have a problem, and I've photographed
wildlife up to 14,000 feet in the Colorado Rockies.
But I have never tested UV versus no UV on the same lens.
I'll try and remember to do that the next time I am at
elevation.

With digital I do not think it is a problem because
the filter responses block out most UV (I'll try and
find the link and post it later). But there is
increased blue light at elevation which needs to be
corrected unless you like excess blue in your photos.
This is true whether or not you use a UV filter.

Roger
Anonymous
January 13, 2005 3:46:11 PM

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

Roger, thank you for your posts on this subject.... I'm looking forward to
seeing that link on digital sensors and UV light sensitivity.
....MTB

"Roger N. Clark (change username to rnclark)" <username@qwest.net> wrote in
message news:41E68C14.1080502@qwest.net...
> Hans-Georg Michna wrote:
> > On Wed, 12 Jan 2005 19:03:49 -0700, "Roger N. Clark (change
> > username to rnclark)" <username@qwest.net> wrote:
> >
> >
> >>MTBike1970 wrote:
> >
> >
> >>>Have you found that digital sensors are as sensitive to UV light as
film?
> >>>i..e. do digital images have that bluish cast in higher altitudes?
> >>>thanks....MTB
> >
> >
> >>At higher elevation, the light is always bluer, regardless
> >>of UV. So you do need to compensate. But this is
> >>easy with digital (at least DSLRs). Now days, I
> >>do not carry 81A or 81B filters with my digital cameras,
> >>like I did with film.
> >>I just change white balance, or shoot raw then adjust
> >>white balance later.
> >
> >
> > Roger,
>
Anonymous
January 13, 2005 6:54:10 PM

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

"Roger N. Clark (change username to rnclark)" <username@qwest.net> wrote:
> Peter Irwin wrote:
>> www.kodak.com/global/images/en/consumer/products/techIn...
>>
>> shows a log exposure range of at least 3.3 (11 stops) from the point
>> on the toe which shows at least 1/3 the average gamma up to the
>> point where they stop the curve where there is only the slightest
>> hint of a shoulder.

> Look again at each curve:
> Blue: flattens out just under 1 (about .9) to a little over 3 (~3.2).
> that is an OD range of ~3.2-.9 = 2.3. 10^2.3 = 200, ~7.6 stops.
>
> green: OD ~ 0.7 to 2.6 = range of 1.9, 10^1.9 = 79 = 6.3 stops
>
> red: OD ~0.2 to 2.0 = range of 1.8, 10^1.8 = 63, 6.0 stops.
>
> My results are in line with Kodak's published data.

Correct me if I'm wrong, but you seem to be looking at the
Y axis numbers which are for film density rather than the
x axis numbers which are for exposure.

On the x axis (exposure) the graph runs from -2.4 (which is
the speed point for ISO 200 film) up to +0.9 where the graph
stops with only a hint of a shoulder. I make that a log exposure
range of 3.3 which is 11 stops.

Peter.
--
pirwin@ktb.net
Anonymous
January 13, 2005 8:09:22 PM

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

In article <1105628997.136905.73220@z14g2000cwz.googlegroups.com>,
stauffer@usfamily.net wrote:

> There is a difference between blue light and UV. Silicon chips are not
> very sensitive to true UV. However, even to the eye the atmosphere has
> a blue haze over far objects. But there are several standard filters
> that can eliminate this blue coloration, such as a minus blue filter or
> skylight filter. The so-called UV filter very necessary for film has
> minimal effect on most colors but cuts down on the shorter blue
> wavelengths. No reasonably priced (absorption) filter has a real sharp
> cutoff with color, so that is why the UV filter may be useful. It is
> really just a weaker type of minus-blue or skylight. Skylight has less
> effect on other colors than minus-blue, whose effect does extend down
> into other colors. Minus blue is fully useful for black and white
> photography, but may be too strong for color (though with color hue
> editing potential for digital, I think it is probably more useful than
> for color film. It makes the color quite "warm."

Not so.

UV filters come from a yellowish to yellow glass which is what you seem
to be saying.

However a skylight filter is made from salmon colored glass and acts as
a warming filter. At higher altitudes, beach and snow scenes a stronger
skylight like the KR3 is best. This is also known as an EF filter as it
also filters out excess blue in non UV flash tubes on electronic flash
(but will not prevent fluorescence in objects with brighteners or that
otherwise chance color from UV in flash systems. At higher altiitudes a
KR 6 is usually best. Otherwise the basic skylight is the KR 1.5. The KR
series is additive so if KR3 is too little warming and a KR6 too much a
KR 1.5 can be used with a KR3 for an intermediate strength between a KR
3 and a KR6.

--
To reply no_ HPMarketing Corp.
Anonymous
January 13, 2005 10:31:07 PM

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

"Mitch" <lawdoggys3@hotmail.com> wrote:

> If you have
>quality glass (i.e. Canon L or Nikkor) are you defeating your good glass by
>putting a UV filter in front?

I believe so. I don't put anything in front of the lens unless there's a
specific need to improve the image quality. I always use hard lens hoods on
all my lenses. Helps improve contrast *and* serves to protect the front
element.

It's a personal choice. I started off slapping one on every lens. Just to
be safe. The first time I went out in public with an expensive lens
"unprotected" was very nerve racking to me. I don't think about it anymore.

If having something on your lens makes you feel better, then don't worry.
If you buy quality filters, your image won't usually be degraded by that
much. You will almost certainly lose some contrast, especially if you're
shooting into the light.

--
Eric
http://canid.com/
Anonymous
January 14, 2005 1:30:45 AM

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

Peter Irwin wrote:

> "Roger N. Clark (change username to rnclark)" <username@qwest.net> wrote:
>
>>Peter Irwin wrote:
>>
>>>www.kodak.com/global/images/en/consumer/products/techIn...
>>>
>>>shows a log exposure range of at least 3.3 (11 stops) from the point
>>>on the toe which shows at least 1/3 the average gamma up to the
>>>point where they stop the curve where there is only the slightest
>>>hint of a shoulder.
>
>
>>Look again at each curve:
>>Blue: flattens out just under 1 (about .9) to a little over 3 (~3.2).
>> that is an OD range of ~3.2-.9 = 2.3. 10^2.3 = 200, ~7.6 stops.
>>
>>green: OD ~ 0.7 to 2.6 = range of 1.9, 10^1.9 = 79 = 6.3 stops
>>
>>red: OD ~0.2 to 2.0 = range of 1.8, 10^1.8 = 63, 6.0 stops.
>>
>>My results are in line with Kodak's published data.
>
>
> Correct me if I'm wrong, but you seem to be looking at the
> Y axis numbers which are for film density rather than the
> x axis numbers which are for exposure.
>
> On the x axis (exposure) the graph runs from -2.4 (which is
> the speed point for ISO 200 film) up to +0.9 where the graph
> stops with only a hint of a shoulder. I make that a log exposure
> range of 3.3 which is 11 stops.
>
> Peter.

OOPS! That was stupid of me. You are correct.
I guess that's what I get for trying to hurry.
I'll look at it again and get back to you after the Cassini
Titan landing. I had planned to overlay the published
curve with mine to see the difference. I'll do that
as soon as I have time.

Roger
Anonymous
January 14, 2005 10:17:55 AM

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

I guess, in reading my post, that I wasn't real clear. It is not the
UV light per se that is the problem it is the blue stuff. If one used
a perfect cutoff UV filter (very expensive- not readily available in
consumer market) it wouldn't help the blue haze problem. Most filters
popularly sold as UV filters do also cut out part of the shorter wave
blue spectrum, and that is what is really needed.
Anonymous
January 17, 2005 12:53:59 AM

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

Peter Irwin wrote:

> "Roger N. Clark (change username to rnclark)" <username@qwest.net> wrote:
>
>>> while film captures about 4.
>>
>>4 orders of magnitude, 10,000, is beyond even the wildest claims
>>I have ever heard. Commonly cited is 7 stops for print film,
>>and 5 stops for slide film. 7 stops = 2^7 = 128, 5 stops = 32.
>>
>>On this page:
>>http://clarkvision.com/imagedetail/dynamicrange2
>>I show Kodak Gold 200 has about 7 stops (a consumer print film), and
>>Fujichrome Velvia has about 4 stops (a professional slide film)
>>of dynamic range.
>
>
> These numbers appear to be rather less than one would suppose
> from looking at the manufacturers' H&D curves.
>
> For instance Kodak Gold 200 -
> www.kodak.com/global/images/en/consumer/products/techIn...
>
> shows a log exposure range of at least 3.3 (11 stops) from the point
> on the toe which shows at least 1/3 the average gamma up to the
> point where they stop the curve where there is only the slightest
> hint of a shoulder.
>
> I'm puzzled how you only get seven stops exposure range. Even if
> you insist on a minimum exposure a little further up the toe,
> you should be getting at least 10 stops, not 7.

Peter,
I've gotten Kodak's characteristic curve data for Kodak Gold 200
and added it to my data. I've plotted the data in Figure 10 at:
http://clarkvision.com/imagedetail/dynamicrange2

Within the scatter of the points in the study, the two curves agree,
and similar basic trends are observed. The film data for my study was
at a constant high resolution, so film grain dominates the signal at
low intensities. While Kodak's characteristic curve data shows a signal
could be seen over larger dynamic range going into the dark portions
of a scene, that signal would have to be of a large target so many
film grains were averaged. Small detail would be lost in the noise.
The digital sensor, however, has much lower noise in the dark
portions of the scene, by factors of 10 and more!

I think this explains how some have said, and even shown, film
can detect a subject over 10+ photographic stops. The problem
is, it can not be done for a small subject, e.g. the size of
a pixel or two like can be done with a digital camera sensor.

Roger
Anonymous
January 18, 2005 11:47:00 PM

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

Roger N. Clark (change username to rnclark) wrote:

> Hans-Georg Michna wrote:
>
>> On Wed, 12 Jan 2005 19:03:49 -0700, "Roger N. Clark (change
>> username to rnclark)" <username@qwest.net> wrote:
>>
>>
>>> MTBike1970 wrote:
>>
>>
>>
>>>> Have you found that digital sensors are as sensitive to UV light as
>>>> film?
>>>> i..e. do digital images have that bluish cast in higher altitudes?
>>>> thanks....MTB
>>
>>
>>
>>> At higher elevation, the light is always bluer, regardless
>>> of UV. So you do need to compensate. But this is
>>> easy with digital (at least DSLRs). Now days, I
>>> do not carry 81A or 81B filters with my digital cameras,
>>> like I did with film.
>>> I just change white balance, or shoot raw then adjust
>>> white balance later.
>>
>>
>>
>> Roger,
>>
>> when you actually get high UV levels, don't you need a UV filter
>> to keep the pictures sharp? Or do the lenses or sensors already
>> filter out UV light?
>>
>> Hans-Georg
>>
>
> That is a good question. I do not know the answer because
> I always have on my UV filters, except on my 500mm f/4 lens.
> The 500 does not have a problem, and I've photographed
> wildlife up to 14,000 feet in the Colorado Rockies.
> But I have never tested UV versus no UV on the same lens.
> I'll try and remember to do that the next time I am at
> elevation.
>
> With digital I do not think it is a problem because
> the filter responses block out most UV (I'll try and
> find the link and post it later). But there is
> increased blue light at elevation which needs to be
> corrected unless you like excess blue in your photos.
> This is true whether or not you use a UV filter.
>
> Roger
>
Here is the link I have to the Canon 10D and D70 spectral response:
(it is way down on the page).

http://astrosurf.com/buil/d70v10d/eval.htm

Lots of other good stuff here too. The responses seem to
zero out at about 3800 angstroms.

Roger
Anonymous
January 21, 2005 5:21:27 AM

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

"Roger N. Clark (change username to rnclark)" <username@qwest.net> wrote:
> I've gotten Kodak's characteristic curve data for Kodak Gold 200
> and added it to my data. I've plotted the data in Figure 10 at:
> http://clarkvision.com/imagedetail/dynamicrange2
>
> Within the scatter of the points in the study, the two curves agree,
> and similar basic trends are observed. The film data for my study was
> at a constant high resolution, so film grain dominates the signal at
> low intensities. While Kodak's characteristic curve data shows a signal
> could be seen over larger dynamic range going into the dark portions
> of a scene, that signal would have to be of a large target so many
> film grains were averaged. Small detail would be lost in the noise.
> The digital sensor, however, has much lower noise in the dark
> portions of the scene, by factors of 10 and more!
Hi Roger,

I've taken a while to digest this. For normal exposure of scenes of
moderate dynamic range (50:1 or so) the average part of the scene
will be only about 10 times the speed point on the toe. 200 speed
negative film has a speed point of at log exposure of -2.4, so the
average part of the scene will be around -1.4.

I know exceedingly little about digital sensors and I don't know
what part of the curve gets used at what exposure. But it seems
to me that the x axis on your graph is based on digital values
rather than the amount of exposure required to get to that
point on the curve. Could you clear this up for me?
It would be nice to have overlaid curves where the x-axis
is based on exposure because it would make it much easier
for me to picture what is going on.

Do you have a book recommendation for a good technical
overview of digital photography? I've been thinking about
getting the current (9th) edition of The Manual of Photography
edited by Jacobson et al. It is supposed to be a continuation
of the Ilford Manual (of which I have several editions) with
a substantial amount of information about digital photography.

>I think this explains how some have said, and even shown, film
>can detect a subject over 10+ photographic stops. The problem
>is, it can not be done for a small subject, e.g. the size of
>a pixel or two like can be done with a digital camera sensor.

Colour negative film has a lot of grain noise on the lower part
of the curve. This is covered up to a large extent by the fact
that the noisiest parts of the negative are printed as near black,
but explains why underexposed colour negatives make very
grainy prints. A stop of so more exposure than your light meter
suggests can significantly reduce the amount of grain visible
in the print and the latitude of modern film allows this.

Peter.
--
pirwin@ktb.net
!