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[OM] Red colo(u)r clipping [was Re: #117]

Subject: [OM] Red colo(u)r clipping [was Re: #117]
From: Moose <olymoose@xxxxxxxxx>
Date: Thu, 26 Jun 2008 23:19:59 -0700
Chuck Norcutt wrote:
> Thanks to Dr. Exposition.  
That the fellow always going to Expos, meeting and conferences?
> If he hits me over the head a few more times with "look at the histogram" it 
> may finally sink in.
>   
Would that it were so easy. If you look at the histogram for the whole 
image, there are clipped highlights in all three channels. There are 
more in the red channel, but not an apparently troubling amount. The 
histograms in the sample I posted are for the smallish area outlined on 
the image. In that limited area, what is happening to the red color is 
obvious.

I'm not sure why the problem seems to be particularly apparent with red, 
but it is so from experience. As Wayne H. proposed: "It may be a digital 
thing, some flowers reflect strongly outside the visible spectrum and 
digital often behaves differently to film there (e.g. if there is a  
strong IR response)."

I know this was a film image, but there is no reason a particularly 
bright, strongly red flower with lots of IR might not have the same 
effect on film. I don't believe the chemical composition of film has 
such narrow frequency cut-offs that some IR sensitivity is not necessary 
to capture all visible reds. I do think the effect is more common with 
digital, though.

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.
>   
One thing to try is taking intentionally underexposed back-up shots of 
such flowers. As long as the reds aren't blown, you should be able to 
get brightness and tonal distribution correct in post.

I suppose a UV or 1A filter wouldn't hurt for the poppies. Perhaps even 
an 80A and a neutral colour reference card in a shot to give proper 
correction for the cast it will give normal colours.

Moose - on behalf of the elusive (illusive? illustrative? illustrious? 
illuminating? alliterative? allusive?...) Dr. Exposition

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