| Author |
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Rich
Guest
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 Posted:
Fri Oct 28, 2005 4:27 am Post subject:
Film still better with colours than digital? |
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Seems like digitals have two problem areas;
Bright scenes can really alter colours from reality
and reds seem to be difficult to render as well as other
colours. Examples might be a bright blue sky that has been
overexposed to a degree and whose colour has shifted to the
cyan and red flowers when compared to flowers of other colours.
There is something odd about the
texture of the red flowers. That said, has anyone shot, then
digitized a good quality 35mm negative and compared it to the output
from one of the $1000 digitals recently?
I saw a comparison in a recent mag of Velvia versus digital and
it seemed to bear this out, but the pictures were too small to
be sure.
-Rich
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David J. Littleboy
Guest
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| Posted:
Fri Oct 28, 2005 4:41 am Post subject:
Re: Film still better with colours than digital? |
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"Rich" <none@none.com> wrote:
| Quote: | Seems like digitals have two problem areas;
Bright scenes can really alter colours from reality
and reds seem to be difficult to render as well as other
colours.
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Bright scenes aren't a problem: just expose correctly. Contrasty scenes are
hard, but with careful exposure and careful RAW conversion, DSLRs do almost
as well in the highlights and much better in the shadows.
Reds are hard. I pull out all the red books (since the covers have subtly
different shades) from my bookshelves every time I get a new digital camera
and see how well I can persuade it to do, and it's always depressing. But
film doesn't do any better.
Every _quantitative_ comparison I've ever seen shows digital to be far
better than film in color accuracy.
Both measure and represent an infinite spectrum with three colors, and thus
can be expected to do very similar things.
| Quote: | I saw a comparison in a recent mag of Velvia versus digital and
it seemed to bear this out, but the pictures were too small to
be sure.
|
Velvia is a serious joke in terms of color accuracy: it's designed to be
extreme. The reds in particular are off the wall. That's why we landscape
types like it. Also, it's an extremely high contrast material with almost no
ability to handle scenes with a wide range of brightnesses.
So Velvia is a funny film to bring up, since it is particularly bad at the
two areas you mentioned to be of concern.
David J. Littleboy
Tokyo, Japan |
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Rich
Guest
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| Posted:
Sat Oct 29, 2005 4:40 am Post subject:
Re: Film still better with colours than digital? |
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On Fri, 28 Oct 2005 10:08:16 +0900, "David J. Littleboy"
<davidjl@gol.com> wrote:
| Quote: | "Rich" <none@none.com> wrote:
Seems like digitals have two problem areas;
Bright scenes can really alter colours from reality
and reds seem to be difficult to render as well as other
colours.
Bright scenes aren't a problem: just expose correctly. Contrasty scenes are
hard, but with careful exposure and careful RAW conversion, DSLRs do almost
as well in the highlights and much better in the shadows.
|
Major issue is ground and sky shots. Unless you are shooting 180
degrees away from the sun and on a day with dry air, chances are the
sky burns out if you expose correctly for the land. The blue colour
is definitely off if you try to bring the sky down to a normal
brightness in post-processing. Varies with camera too.
| Quote: |
Reds are hard. I pull out all the red books (since the covers have subtly
different shades) from my bookshelves every time I get a new digital camera
and see how well I can persuade it to do, and it's always depressing. But
film doesn't do any better.
Every _quantitative_ comparison I've ever seen shows digital to be far
better than film in color accuracy.
Both measure and represent an infinite spectrum with three colors, and thus
can be expected to do very similar things.
I saw a comparison in a recent mag of Velvia versus digital and
it seemed to bear this out, but the pictures were too small to
be sure.
Velvia is a serious joke in terms of color accuracy: it's designed to be
extreme. The reds in particular are off the wall. That's why we landscape
types like it. Also, it's an extremely high contrast material with almost no
ability to handle scenes with a wide range of brightnesses.
So Velvia is a funny film to bring up, since it is particularly bad at the
two areas you mentioned to be of concern.
David J. Littleboy
Tokyo, Japan
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Yes, I was going by what one of the articles said. But what you say
about liking a striking film for landscapes is true enough. Some of
the landscapes you see in magazines shot by pros are really off the
charts when it comes to colour. The neon green grass, etc, but it's
not confined to film shots.
-Rich |
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Rich
Guest
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| Posted:
Sat Oct 29, 2005 4:40 am Post subject:
Re: Film still better with colours than digital? |
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On 27 Oct 2005 22:56:25 -0700, "Ace" <rwatson767@aol.com> wrote:
| Quote: | Rich
I have a Canon 20D. I download the files to my computer and print to an
Epson 2200. Reds are no problem. Short of shifting the Hue way too far
the printer seems to do exactly as I want. Even to the point of
correcting what I do with the computer.
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I'm not familiar with the dynamics of the 20D on reds itself. What I
find is that the "look" not so much the colour of red is off in
digital images. It's sometimes imparts an irridescence that has to be
carefully dealt with in post-processing to eliminate.
| Quote: |
Also there is a possibility that you have not set up everything on your
the camera as it should be.
Bob AZ
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I think everyone has a "favorite" setting for cameras concerning
saturation, contrast, etc. I leave mine alone but I will
experiment a bit with it.
-Rich |
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Scott W
Guest
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| Posted:
Sat Oct 29, 2005 4:40 am Post subject:
Re: Film still better with colours than digital? |
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Rich wrote:
| Quote: | Major issue is ground and sky shots. Unless you are shooting 180
degrees away from the sun and on a day with dry air, chances are the
sky burns out if you expose correctly for the land. The blue colour
is definitely off if you try to bring the sky down to a normal
brightness in post-processing. Varies with camera too.
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It is best to expose for the sky and then lighten the ground as needed.
You can either select the ground and lighten it or reduce the contrast
for the whole photo. Tryng to bring the sky down after the fact is a
lossing battle.
Scott |
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Bill Funk
Guest
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| Posted:
Sat Oct 29, 2005 4:40 am Post subject:
Re: Film still better with colours than digital? |
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On 28 Oct 2005 12:46:11 -0700, eawckyegcy@yahoo.com wrote:
| Quote: | Bill Funk wrote:
eawckyegcy seems to be sayign that analog film use prodiuces no waste;
that's what "the waste stream is O(number of pictures taken)" means,
right?
It is the letter "O" (the one between N and P), not a zero.
How does that work? I mean, there's obviously waste, so how does that
work?
http://en.wikipedia.org/wiki/Big_O_notation
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My head hurts. :-)
--
Bill Funk
Replace "g" with "a"
funktionality.blogspot.com |
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223rem
Guest
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| Posted:
Sun Oct 30, 2005 1:17 am Post subject:
Re: Film still better with colours than digital? |
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Chris Brown wrote:
| Quote: | In article <CqE8f.497296$_o.177024@attbi_s71>,
223rem <223rem@sbcglobal.com> wrote:
eawckyegcy@yahoo.com wrote:
For analog photography, the waste stream is O(number of pictures
taken).
For digital photography, the waste stream is O(number of cameras).
Dare to do the arithmetic.
Same thing, they're linearly related :)
'Tis true that these are both O(N), but they're different Ns.
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the two Ns are differ by a constant factor. So they go to inf
equally 'fast' |
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Ilya Zakharevich
Guest
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| Posted:
Sun Oct 30, 2005 9:16 pm Post subject:
Re: Film still better with colours than digital? |
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[A complimentary Cc of this posting was sent to
Roger N. Clark (change username to rnclark)
<username@qwest.net>], who wrote in article <4364E9BF.2070203@qwest.net>:
| Quote: | E.g., 3 colors are enough to obtain a honest representation of
Don't you mean 3 channels? The eye sees far more than 3 colors!
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Yes, thanks for correction.
| Quote: | "what the eye can see in this lightening conditions".
All you need is that color curves of eye cones can be well
approximated by linear combinations of color curves of the sensels.
The color response of a system is a numerical integration
over the spectral response of the channel bandpass times the
sensor spectral response times the spectral transmission of the
optics and filters times the spectral response of the light source.
That is not a linear function.
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Would you be so kind to explain what you mean by "a linear function"?
[All processes you consider are linear in usual sense of this word.]
[It is the second time you claim that integration is a non-linear
process. At least the second time when answering my posts. :-( You
were already corrected once...]
| Quote: | However, consider the following question:
"this shot is made in tungsten light. Now what the eye would see if
it were in sun light?"
This requires approximating the cone sensitivity curves *multiplied*
by the quotient of spectral densities of tungsten and sun lights.
Obviously, with 3 types of sensels, if you can answer one question
good enough, you won't be able to answer the other one.
You can if the system spectral response matches that of the eye.
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Nope. As I said, you need to match
Eye_response(w) * Desired_lightening(w) / Actual_lightening(w).
Here w is the light wavelength.
Hope this helps,
Ilya |
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Scott W
Guest
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| Posted:
Mon Oct 31, 2005 3:37 am Post subject:
Re: Film still better with colours than digital? |
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Ilya Zakharevich wrote:
| Quote: | Eye_response(w) * Desired_lightening(w) / Actual_lightening(w).
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If I might restate what I believe you are saying
If you take a photo under one set of lighting you have know way to know
how it will exactly look under other lighting. The more colors
filters that are used the better you should be able to do at this. If
we used a color wheel with narrow band filters every 5 nm and if the
lighting was fairly broad band and if we knew the spectrum of the
lighting then we could produce a photo as if it were under any lighting
condition.
There are of course limits to this, here in Hawaii we use low pressure
sodium lights, these have a very narrow spectrum and it would be just
about impossible to take a photo under them that came even close to the
real colors.
Having said all that digital cameras will still come closer then film
in recording colors.
Scott |
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Roger N. Clark (change us
Guest
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| Posted:
Mon Oct 31, 2005 5:40 am Post subject:
Re: Film still better with colours than digital? |
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Roger N. Clark (change username to rnclark) wrote:
| Quote: | Chris,
These are great references. Thanks. I've been searching for a while
for digital data for the xyz color matching functions (e.g. an ascii
listing as a function of wavelength). Do you have any idea where
I might find it? I searched through the above pages but did not see it.
An equation would be fine too.
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Found it! After searching on Wyszecki & Stiles I found
a treasure of data at: http://cvision.ucsd.edu
Roger |
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Roger N. Clark (change us
Guest
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| Posted:
Mon Oct 31, 2005 5:40 am Post subject:
Re: Film still better with colours than digital? |
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Chris Brown wrote:
| Quote: | In article <djsn0f$ca6$1@agate.berkeley.edu>,
Ilya Zakharevich <nospam-abuse@ilyaz.org> wrote:
E.g., 3 colors are enough to obtain a honest representation of
"what the eye can see in this lightening conditions".
All you need is that color curves of eye cones can be well
approximated by linear combinations of color curves of the sensels.
Not true - some colours within the human vision gamut are repesented by
negative values in a system based on 3 priamry colours. Some colours have
one of the channels being literally darker than black. You can represent the
full gamut using 3 primaries without resprting to negative values, but the
primaries you chose don't correspond to wavelengths of light.
Disclaimer, IANA biologist, so these guys can almost cenrtainly explain it
better than I can:
http://www.handprint.com/HP/WCL/color6.html (search for "out of gamut").
http://hyperphysics.phy-astr.gsu.edu/hbase/vision/colhist.html
http://en.wikipedia.org/wiki/CIE_1931_color_space
The last one does a reasonable job of explaining, mathematically, why it's
not possible to cover the human gamut with 3 values representing real
wavelengths.
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Chris,
These are great references. Thanks. I've been searching for a while
for digital data for the xyz color matching functions (e.g. an ascii
listing as a function of wavelength). Do you have any idea where
I might find it? I searched through the above pages but did not see it.
An equation would be fine too.
Roger |
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Chris Brown
Guest
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| Posted:
Mon Oct 31, 2005 5:40 am Post subject:
Re: Film still better with colours than digital? |
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In article <djsn0f$ca6$1@agate.berkeley.edu>,
Ilya Zakharevich <nospam-abuse@ilyaz.org> wrote:
| Quote: | E.g., 3 colors are enough to obtain a honest representation of
"what the eye can see in this lightening conditions".
All you need is that color curves of eye cones can be well
approximated by linear combinations of color curves of the sensels.
|
Not true - some colours within the human vision gamut are repesented by
negative values in a system based on 3 priamry colours. Some colours have
one of the channels being literally darker than black. You can represent the
full gamut using 3 primaries without resprting to negative values, but the
primaries you chose don't correspond to wavelengths of light.
Disclaimer, IANA biologist, so these guys can almost cenrtainly explain it
better than I can:
http://www.handprint.com/HP/WCL/color6.html (search for "out of gamut").
http://hyperphysics.phy-astr.gsu.edu/hbase/vision/colhist.html
http://en.wikipedia.org/wiki/CIE_1931_color_space
The last one does a reasonable job of explaining, mathematically, why it's
not possible to cover the human gamut with 3 values representing real
wavelengths. |
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Ilya Zakharevich
Guest
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| Posted:
Tue Nov 01, 2005 3:57 am Post subject:
Re: Film still better with colours than digital? |
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[A complimentary Cc of this posting was sent to
Roger N. Clark (change username to rnclark)
<username@qwest.net>], who wrote in article <4366C59A.6020707@qwest.net>:
| Quote: | Your are ion a different paradigm. Some are talking about current
real world 3-channel systems. You are considering a many channel
system. What Chris said is correct for 3-channel systems.
|
a) 3-channel system is a particular kind of many-channels system. My
argument is equally applicable to 3-channel and 100-channel systems.
b) "Real world" uses non only 3-channel systems. Some digicams are
4-channels.
| Quote: | The 700nm being the peak of red response looks very fishy, which makes
the rest of the discussion suspicious too. Probably they meant 600nm
(do not have my Marr at hand now...)?
The page does not say that 700 nm is the peak red response.
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Did you *actually* read the article? Use "Find" button in your browser.
The 700 nm wavelength ... was chosen because it is at the peak of
the eye's red response
Hope this helps,
Ilya |
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Peter Irwin
Guest
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| Posted:
Tue Nov 01, 2005 4:50 am Post subject:
Re: Film still better with colours than digital? |
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Ilya Zakharevich <nospam-abuse@ilyaz.org> wrote:
| Quote: |
Did you *actually* read the article? Use "Find" button in your browser.
The 700 nm wavelength ... was chosen because it is at the peak of
the eye's red response
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That's badly phrased, but I think what they meant was that
700 nm is the best wavelength to choose for getting a pure
red.
I know nothing about the subject apart from a bit of
reading, but section 340 "limitations of additive synthesis"
in the Ilford Manual of Process Work by L.P. Clerk (5th ed 1951)
has a quite interesting discussion of this.
Peter.
--
pirwin@ktb.net |
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Roger N. Clark (change us
Guest
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| Posted:
Tue Nov 01, 2005 5:40 am Post subject:
Re: Film still better with colours than digital? |
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Ilya Zakharevich wrote:
| Quote: | [A complimentary Cc of this posting was sent to
Chris Brown
cpbrown@ntlworld.no_uce_please.com>], who wrote in article <dn4g33-h8l.ln1@narcissus.dyndns.org>:
E.g., 3 colors are enough to obtain a honest representation of
"what the eye can see in this lightening conditions".
All you need is that color curves of eye cones can be well
approximated by linear combinations of color curves of the sensels.
Not true - some colours within the human vision gamut are repesented by
negative values in a system based on 3 priamry colours.
Irrelevant. If you have an n-channel receiver, and can represent the
spectral sensitivity curves of cones as linear combinations of
sensitivity curves of the channels, all *is* tip-top. Your channels
will (obviously) get positive readings; but the sign of the linear
combination may be negative. Depend on what color space (encoding)
you choose for the result.
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Ilya,
Your are ion a different paradigm. Some are talking about current
real world 3-channel systems. You are considering a many channel
system. What Chris said is correct for 3-channel systems.
| Quote: | http://en.wikipedia.org/wiki/CIE_1931_color_space
The last one does a reasonable job of explaining, mathematically, why it's
not possible to cover the human gamut with 3 values representing real
wavelengths.
The 700nm being the peak of red response looks very fishy, which makes
the rest of the discussion suspicious too. Probably they meant 600nm
(do not have my Marr at hand now...)?
|
The page does not say that 700 nm is the peak red response.
You may be confusing CIE color space, spectral response and
the definition of primary colors. The page is correct, there
is nothing "suspicious."
Roger |
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