[pure-silver] Re: OT: Color IQ Test
- From: Jean-David Beyer <jeandavid8@xxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Mon, 09 Nov 2009 09:33:36 -0500
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Eric Neilsen Photo wrote:
| Interesting story. I am sure that after a few go 'rounds with the pill
| pile, you were ready to take a few your self? Being able to see the
| difference is just the beginning though, as you still had to contend
| with the limits of film, chemistry, paper, and inks through out the
| whole process. That represents the science side of photography. Then
| there is the whole art side of photography where we get to play with
| color or lack there of.
|
The human eye is extremely sensitive to slight differences in hue,
lightness, and saturation iff the items in question are next to one
another. It is very easy to distinguish these things unless you are
color blind. If you look at a monitor, it does not have to be very good
in terms of color rendition provided that there are enough bits supplied
to distinguish differences of the light. 8 bits per color (R,G, B) are
not enough for accurate color work. If you do the equivalent of a gray
scale, you can see the steps with 8 bits. But, while the colors in that
test were of relatively low saturation and did not employ a wide range
of lightness, any old monitor that I know of would be sufficient to do
this test well if you knew what to look for.
Not so easy is identifying a color. That takes a lot of work. It took me
and my fellow trained observers several months to learn the 4000 or so
color chips in the Munsell Book of Color. And we were retested about
once a week, IIRC. Hue was essentially given in 40 steps; e.g. 2.5 red,
5 red, 7.5 red, 10 red, 2.5 yellow-red, etc. Lightness was given in ten
steps from 0 (black) to 10 (almost 100% diffuse reflectance) and
saturation went from 0 (no hue) to about 16 (extremely saturated). We
were allowed to be one step off in lightness, 2 steps off in saturation.
Hue is more complicated. It was easy to tell the 4 steps of red, but for
the other colors, just hitting the hue correctly was considered OK. I
have not practiced this for decades now, but at the time we did 100
chips at a time and could not refer to the color book (for various
reasons) when doing the test. We looked at the chips directly for
testing under an artificial (reproducible) light balanced to D5000,
IIRC, but for the research we were doing (studies of picture coding for
digital TV transmissions) we looked at projected images on a ground
glass screen from photographic transparencies.
- --
~ .~. Jean-David Beyer Registered Linux User 85642.
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