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[OM] A Redder Channel [was More Red [was 2014 Orchid Show]]

Subject: [OM] A Redder Channel [was More Red [was 2014 Orchid Show]]
From: Moose <olymoose@xxxxxxxxx>
Date: Sun, 20 Apr 2014 14:37:40 -0700
More about red channels and what happens when you convert color spaces. And why 
Joel may have done his orchids 
perfectly, yet I found clipped red channels in some.

This expands on my last posted image comparisons by adding histograms. 
<http://www.moosemystic.net/Gallery/tech/BrowserColorSpaces/TulipH.htm>

Color space conversion were done using Perceptual intent, which is, I think, 
why they all appear the same.

Apparently, none of the colors, ACR default or after pretty strong LCE and 
Curves, exceeds the aRGB color space, so the 
ProPhoto and aRGB histograms are identical.

But, in order to maintain the same appearance the sRGB conversions move the 
channels up toward the top. As this was shot 
at -2/3 EV, the ACR default version still doesn't clip. But the post version 
clips a fair amount.

Soooooo ... If you convert from a larger space to sRGB as the last step, and 
don't check the histogram, or if you post 
in a gallery that converts aRGB to sRGB, most likely with a less sophisticated 
conversion engine, it's possible to have 
a clipped channel without knowing it.

I was at first disappointed that this particular image doesn't show the effects 
of clipping. That it is not nearly as 
heavily clipped and the orchids certainly helps. The striations and other color 
variations also help it avoid that 'big 
blobs of one color without detail; effect that's common in red-orange-yellow 
flower images.

Perhaps it's just as well, though. We've already seen the effect on a couple of 
Joel's web images. To not have it 
visible here shows how tricky these shots can be. And how proper technique in 
shooting and processing can avoid trouble.

As shown in my previous post, one may avoid one big pitfall by posting aRGB 
JPEGs, at least for the huge majority of 
viewers using current version of the big four browsers.

Unshorn Moose

-- 
What if the Hokey Pokey *IS* what it's all about?
-- 
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