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Colour blindness, photography and colour management

 
 
Tor Lillqvist
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      05-18-2004
I am slightly red-green colour blind. I haven't had my colour perception
amomalies exactly measured or anything, though. It's just something that
was noticed at school as a teenager, using those Ishihara plates. As is
common, it was quite a surprise to me, I hadn't noticed anything wrong
earlier... (There went my childhood dream of becoming a train driver

I don't know whether I have protanomaly or deuteranomaly. Presumably I
am not blatantly dichromatic, though, as I do see the difference between
red and green in general. It's just some hues that are hard to
distinguish for me, but apparently easy for others, etc.

Now, I have been thinking about how colour blindness relates to digital
photography and colour management in particular. Is a colour managed
workflow worth it at all for me? Colour management (and the whole CIE
colour model) is based on the "standard observer"...

Even if I would have a calibrated and profiled monitor, and use a
profiled printer (either an own or use a on-line service bureau), when I
tweak an image on my machine before sending it to the printer, I tweak
it to look correct for me. But presumably the colours might well be
quite off to a person with normal colour vision?

And even if I would consider only myself, and ignore showing my pics to
other people: Doesn't colour management strive to make images look the
same when produced by different devices (modulo the rendering intent)
for people with normal vision? Isn't it entirely possible, that as my
colour receptors have different spectral response than those of the
standard observer, an image on the monitor and when printed won't look
at all the same to me, even if it would to a person with normal colour
vision?

Basically, I guess what I am asking is whether it makes any sense for me
to invest some hundreds of euros in colour management hardware and
software, if it by design won't work for me anyway...

Thanks in advance for any insights people can share.

--tml
 
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Beck
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Posts: n/a
 
      05-18-2004

"Tor Lillqvist" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> I am slightly red-green colour blind. I haven't had my colour perception
> amomalies exactly measured or anything, though. It's just something that
> was noticed at school as a teenager, using those Ishihara plates. As is
> common, it was quite a surprise to me, I hadn't noticed anything wrong
> earlier... (There went my childhood dream of becoming a train driver
>
> I don't know whether I have protanomaly or deuteranomaly. Presumably I
> am not blatantly dichromatic, though, as I do see the difference between
> red and green in general. It's just some hues that are hard to
> distinguish for me, but apparently easy for others, etc.
>
> Now, I have been thinking about how colour blindness relates to digital
> photography and colour management in particular. Is a colour managed
> workflow worth it at all for me? Colour management (and the whole CIE
> colour model) is based on the "standard observer"...
>
> Even if I would have a calibrated and profiled monitor, and use a
> profiled printer (either an own or use a on-line service bureau), when I
> tweak an image on my machine before sending it to the printer, I tweak
> it to look correct for me. But presumably the colours might well be
> quite off to a person with normal colour vision?
>
> And even if I would consider only myself, and ignore showing my pics to
> other people: Doesn't colour management strive to make images look the
> same when produced by different devices (modulo the rendering intent)
> for people with normal vision? Isn't it entirely possible, that as my
> colour receptors have different spectral response than those of the
> standard observer, an image on the monitor and when printed won't look
> at all the same to me, even if it would to a person with normal colour
> vision?
>
> Basically, I guess what I am asking is whether it makes any sense for me
> to invest some hundreds of euros in colour management hardware and
> software, if it by design won't work for me anyway...
>
> Thanks in advance for any insights people can share.



That is not meant to sound flippant or offensive, but have you considered
specialising in monochrome pictures only?
I have an acquaintance who is colour blind, but he excels in black and white
images.


 
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Mark Weaver
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      05-18-2004
As I understand it, the point of color management is to get the same results
across devices (or as nearly as possible given the differences). So the
point of color management for a color-blind person would be to have the
image look 'right' to you both on your monitor and after you print it (or
have it printed). As to whether or not it looks right to others -- have you
run into an actual image where you thought the colors looked right but
others thought they were off?

Mark


"Tor Lillqvist" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> I am slightly red-green colour blind. I haven't had my colour perception
> amomalies exactly measured or anything, though. It's just something that
> was noticed at school as a teenager, using those Ishihara plates. As is
> common, it was quite a surprise to me, I hadn't noticed anything wrong
> earlier... (There went my childhood dream of becoming a train driver
>
> I don't know whether I have protanomaly or deuteranomaly. Presumably I
> am not blatantly dichromatic, though, as I do see the difference between
> red and green in general. It's just some hues that are hard to
> distinguish for me, but apparently easy for others, etc.
>
> Now, I have been thinking about how colour blindness relates to digital
> photography and colour management in particular. Is a colour managed
> workflow worth it at all for me? Colour management (and the whole CIE
> colour model) is based on the "standard observer"...
>
> Even if I would have a calibrated and profiled monitor, and use a
> profiled printer (either an own or use a on-line service bureau), when I
> tweak an image on my machine before sending it to the printer, I tweak
> it to look correct for me. But presumably the colours might well be
> quite off to a person with normal colour vision?
>
> And even if I would consider only myself, and ignore showing my pics to
> other people: Doesn't colour management strive to make images look the
> same when produced by different devices (modulo the rendering intent)
> for people with normal vision? Isn't it entirely possible, that as my
> colour receptors have different spectral response than those of the
> standard observer, an image on the monitor and when printed won't look
> at all the same to me, even if it would to a person with normal colour
> vision?
>
> Basically, I guess what I am asking is whether it makes any sense for me
> to invest some hundreds of euros in colour management hardware and
> software, if it by design won't work for me anyway...
>
> Thanks in advance for any insights people can share.
>
> --tml



 
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Al Denelsbeck
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Posts: n/a
 
      05-18-2004
Tor Lillqvist <(E-Mail Removed)> wrote in
news:(E-Mail Removed):

> I am slightly red-green colour blind...

<snip>
> Basically, I guess what I am asking is whether it makes any sense for me
> to invest some hundreds of euros in colour management hardware and
> software, if it by design won't work for me anyway...
>
> Thanks in advance for any insights people can share.



I would not consider this a significant issue, especially if your
difficulties lie in such a narrow area of the color spectrum.

Unless you're shooting artwork, tile patterns, or something that
basically can be limited to those wavelengths you have difficulties with,
there will almost always be enough of the rest of the spectrum in the image
to judge accurately enough. Most things that might be green, for instance,
are going to be obviously green (grass, foliage, etc), or will transition
across the spectrum to include those areas you can see well. A balloon shot
in high contrast conditions may run the gamut from almost pure white where
it reflects the light, to black in the shadows. By concentrating on those
areas when doing color correction, you shouldn't be off the mark by much,
if any.

And that's part of the secret to color correction anyway - you watch
the highlights, and/or you pick something white that transitions into
shadow. If a white shirt shows a color cast, other than grey, as it goes
into shadow, chances are you need to tweak the color (provided the lighting
spectrum supports this - don't do it for sunset pics, for example, because
they're supposed to be yellow )

But even if this presents a problem, there are other methods. If you
tend to shoot controlled or studio work, you can waste a frame on a color
chart, and as long as the rest of the frames are done in the same lighting
conditions, you can correct the entire session based on the readings from
the chart. A grey card can work too, but tends to be less accurate.

And photo editing programs can help as well. You can snatch a color
sample from some area of the image and look at the actual RGB (or CMYK)
values. Tricky, but with a little practice (and perhaps a guideline chart
or image) you can tweak the colors as needed. Again, this works better in
neutral areas - white, grey, and black. But it goes hand-in-hand with the
chart idea above. This will also work if you ever run into something that
isn't obvious and falls into those problem areas you have - a quick sample
will tell you red or green easily enough.

But to be sure your vision isn't shifted overall (for instance, what
seems pure white to you is actually slightly reddish), correct a few images
and have someone review them. Preferably someone who's done it many times
before - color correction is very subjective until you're used to doing it.
At the same time, use your color sampler to ensure yourself. BUT, only
after your monitor has been reasonably calibrated. Doesn't have to be
fancy, just use a three-color gamma program (like Adobe Gamma) first.

And be wary. The color sampler in Photoshop tends to pick individual
pixels, which in a neutral grey area can still run the gamut of colors. Use
a command, such as the Noise/Median filter or any blur command, to get the
pixels evened out within an area before sampling.

Good luck!


- Al.

--
To reply, insert dash in address to separate G and I in the domain
 
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Bart van der Wolf
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Posts: n/a
 
      05-18-2004

"Al Denelsbeck" <(E-Mail Removed)> wrote in message
news:Xns94ED93612B4DCsandalsatwadinginnet@65.32.1. 8...
SNIP
> And be wary. The color sampler in Photoshop tends to pick
> individual pixels, which in a neutral grey area can still run the
> gamut of colors.


You can set the sampler to a 1, 3 or 5 pixel pixel square to sample from.

Bart

 
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GraemeGill
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Posts: n/a
 
      05-18-2004


Tor Lillqvist wrote:
> I am slightly red-green colour blind. I haven't had my colour perception
> amomalies exactly measured or anything, though. It's just something that
> was noticed at school as a teenager, using those Ishihara plates. As is
> common, it was quite a surprise to me, I hadn't noticed anything wrong
> earlier... (There went my childhood dream of becoming a train driver


> Basically, I guess what I am asking is whether it makes any sense for me
> to invest some hundreds of euros in colour management hardware and
> software, if it by design won't work for me anyway...


I'm no expert on color blindness, but the impression I've got from several
books/articles that lightly cover this topic, is that the majority of
colorblindness is due to weakness in one or more receptors, not a shift
in their spectral sensitivities. If this is indeed the case, then normal
tri-stimulus color matching should be of benefit. For someone who is weak
in distinguishing certain ranges of colors, then "doing it by the numbers"
with a CMS, may be the only way of producing work that can be confidently
viewed by non color deficient viewers.
As with investing in any expensive set of tools, the best thing is to
insist on trying them out, before committing to buy ...

Graeme Gill.

 
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David Kilpatrick
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Posts: n/a
 
      05-19-2004


Tor Lillqvist wrote:

> I am slightly red-green colour blind. I haven't had my colour perception
> amomalies exactly measured or anything, though. It's just something that
> was noticed at school as a teenager, using those Ishihara plates. As is
> common, it was quite a surprise to me, I hadn't noticed anything wrong
> earlier... (There went my childhood dream of becoming a train driver
>
> I don't know whether I have protanomaly or deuteranomaly. Presumably I
> am not blatantly dichromatic, though, as I do see the difference between
> red and green in general. It's just some hues that are hard to
> distinguish for me, but apparently easy for others, etc.
>
> Now, I have been thinking about how colour blindness relates to digital
> photography and colour management in particular. Is a colour managed
> workflow worth it at all for me? Colour management (and the whole CIE
> colour model) is based on the "standard observer"...
>
> Even if I would have a calibrated and profiled monitor, and use a
> profiled printer (either an own or use a on-line service bureau), when I
> tweak an image on my machine before sending it to the printer, I tweak
> it to look correct for me. But presumably the colours might well be
> quite off to a person with normal colour vision?
>
> And even if I would consider only myself, and ignore showing my pics to
> other people: Doesn't colour management strive to make images look the
> same when produced by different devices (modulo the rendering intent)
> for people with normal vision? Isn't it entirely possible, that as my
> colour receptors have different spectral response than those of the
> standard observer, an image on the monitor and when printed won't look
> at all the same to me, even if it would to a person with normal colour
> vision?
>
> Basically, I guess what I am asking is whether it makes any sense for me
> to invest some hundreds of euros in colour management hardware and
> software, if it by design won't work for me anyway...
>
> Thanks in advance for any insights people can share.
>


It will still work. Your colour blindness is only part of the
calibration issue, and in fact the questions of black point, gamma and
brightness of images are critical for good prints - a calibration device
sorts these out as well as trying to make all colours almost match.
Colour calibration is, in any case, not all that successful even with
'eye' type sensors; it's often battling against extreme nonlinearity by
imposing extreme correction curves in very critical areas like the
transitions from deep shadows to visible detail, and can result in odd
effects like greenish hues appearing on these boundaries in prints when
the monitor looks perfect. You might miss seeing such effects and that
would be one risk of using calibration!

After years of using such devices, I tend to calibrate contrast only
now. I accept the different colour 'flavours' of my various monitors and
don't mess with their gain curves, and nor do I adjust my images using
different curves on RGB etc. I just make simple adjustments to
brightness, daylight/white balance, contrast and so on. This works well
enough. I have not used a digital camera yet which had crossed curves!

David

 
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Philip Homburg
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Posts: n/a
 
      05-19-2004
In article <40AA8C68.1060300@not_access.net.au>,
GraemeGill <not_graeme_@not_access.net.au> wrote:
>Tor Lillqvist wrote:
>> I am slightly red-green colour blind. I haven't had my colour perception
>> amomalies exactly measured or anything, though. It's just something that
>> was noticed at school as a teenager, using those Ishihara plates. As is
>> common, it was quite a surprise to me, I hadn't noticed anything wrong
>> earlier... (There went my childhood dream of becoming a train driver

>
>> Basically, I guess what I am asking is whether it makes any sense for me
>> to invest some hundreds of euros in colour management hardware and
>> software, if it by design won't work for me anyway...

>
>I'm no expert on color blindness, but the impression I've got from several
>books/articles that lightly cover this topic, is that the majority of
>colorblindness is due to weakness in one or more receptors, not a shift
>in their spectral sensitivities. If this is indeed the case, then normal
>tri-stimulus color matching should be of benefit. For someone who is weak
>in distinguishing certain ranges of colors, then "doing it by the numbers"
>with a CMS, may be the only way of producing work that can be confidently
>viewed by non color deficient viewers.
>As with investing in any expensive set of tools, the best thing is to
>insist on trying them out, before committing to buy ...


If you take one of those Ishihara plates, convert to 'cone space' (using
Bradford) drop the appropriate channel (red, green, or blue) en convert back
to a normal color space, you can simulate the effects of color blindness
quite well.



--
The Electronic Monk was a labor-saving device, like a dishwasher or a video
recorder. [...] Video recorders watched tedious television for you, thus saving
you the bother of looking at it yourself; Electronic Monks believed things for
you, [...] -- Douglas Adams in Dirk Gently's Holistic Detective Agency
 
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Roger Breton
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      05-20-2004
in article vdechlc8vmgjef5ao2mm4ld0u7@inews_id....q.phic oh.net, Philip
Homburg at http://www.velocityreviews.com/forums/(E-Mail Removed) wrote on 5/19/04 10:48 AM:

> If you take one of those Ishihara plates, convert to 'cone space' (using
> Bradford) drop the appropriate channel (red, green, or blue) en convert back
> to a normal color space, you can simulate the effects of color blindness
> quite well.
>


Is that all the 'Bradford' transform does to a set of XYZ values, convert to
'cone space'?

Is it the same thing as converting from XYZ to LMS then?

Roger Breton

 
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Bart van der Wolf
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      05-20-2004

"Roger Breton" <(E-Mail Removed)> wrote in message
news:BCD210A7.196EE%(E-Mail Removed)...
> in article vdechlc8vmgjef5ao2mm4ld0u7@inews_id....q.phic oh.net,

Philip
> Homburg at (E-Mail Removed) wrote on 5/19/04 10:48 AM:
>
> > If you take one of those Ishihara plates, convert to 'cone space' (using
> > Bradford) drop the appropriate channel (red, green, or blue) en convert

back
> > to a normal color space, you can simulate the effects of color blindness
> > quite well.
> >

>
> Is that all the 'Bradford' transform does to a set of XYZ values, convert

to
> 'cone space'?


A different type of cone space, producing the smallest differences when
converting between illuminants.

http://www.brucelindbloom.com/Eqn_ChromAdapt.html
http://www.brucelindbloom.com/ChromAdaptEval.html


Bart

 
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