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

Subject: [OM] Re: Red colo(u)r clipping [was Re: #117]
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Fri, 27 Jun 2008 08:10:53 -0400
Just in the way of general observation, with both the A1 and the 5D if 
there is a color channel that's clipped it's most likely the red 
channel.  I don't know why.

Chuck Norcutt

Moose wrote:
> 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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