Chris Barker wrote:
> I'm sure that that's a beautiful shot, Graham, but colour looks wrong on my
> monitor. It seems always to be the case with poppies when I take photos:
> digital does not like that colour.
>
Chris, and others who have replied in agreement,
This is a common problem with digital cameras and/or processing that is
especially common with intense reds. The cause is clipping on one colour
channel before others.
You can see the effect in the individual channel histograms in a small
section of the flower image here.
<http://www.moosemystic.net/Gallery/tech/Misc/RedClip.htm>
The original distribution of red in the subject was likely much like
that of green, a narrow, symmetrical distribution. As colour neg film
has a great deal of overexposure latitude, red layer brightness in the
film probably pretty well matched the subject. Somewhere in scanning
and/or processing, the red channel was overexposed, and the right side
of the distribution all ended up with one value.
One visual result of this is a lack of subtle detail in the red
highlights. Another, as noted explicitly by Chuck and implicitly by
others, is a change in colour. In the brightest pixels, the red can't be
increased in proportion to the other channels, so color* casts appear.
In this case, as the blue channel is brighter than green, the color cast
is slightly blue. The reds in the central, shaded portions of the flower
image are clipped much less, so the color is more likely accurate.
The same thing can happen with film, but is less common and/or obvious
because of the exposure characteristics of film vs. digital sensors. The
softer shoulder of the film response curve doesn't sharply clip above a
certain brightness level. In theory, I suppose it's more likely to be
noticeable in slide film than color neg.
I also suppose the same effect could occur on a monitor set too bright,
so that a color channel clips where the others don't.
Moose
* Spelling of colo(u)r in this document is customized to the native
spelling of the poster(s) to whom each individual instance refers.
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