Red channel in RAW is giving me trouble

[fastshutter]

I'm having a problem when I shoot in RAW. My red channel is always

hiting 255 in skin tones when I shoot. I can get it back down if I

adjust the white balence but then picture is to cool. If any body

knows any articles on this or has any help please let me know.<div></div>

[chiswick_john]

look at your white balance setting in the camera - maybe use a grey card to get a custom balance.

[ellis_vener_photography]

overall the screen shot yuou posted looks too red. What camera are you working with?

Have you triedthe calibrate tab and adjusting just the red channel there?

[matt_chamberlain]

What's the idea with the Tint +16?

[paul beiser]

Agree with Ellis, overall your picture looks too red. Also, please note your histogram covers the entire range - it would appear the dynamic range of your scene is too much for the sensor to handle.

 

I would highly recommend Bruce Fraser's "Camera Raw" book. Also, any book by Bruce Fraser is great.

[jeff medkeff anchorage, a]

<p><i>If</i> Ken is always hitting the peak in the red channel <i>when he shoots</i>, the problem is overexposure. Now to sort this out properly, he can take one set of actions to rescue this image, and another set to avoid the problem in future:

 

<p><i>look at your white balance setting in the camera - maybe use a grey card to get a custom balance.</i>

 

<p>This will bring the displayed histogram more into line with the raw histogram and is definitely worth doing: it will help in evaluating exposure in the camera. Don't count on it to solve the problem if you shoot again with the same subject, lights, and exposure settings though.

 

<p><i>What camera are you working with?</i>

 

<p>It looks like he's shooting with a Canon 10D, from the text on the title bar. If so, my 10D red channel goes a little nonlinear near the top of the histogram and gets saturated about a half stop sooner than the green channel. Perhaps this is happening here. In any case, Ken, I'd run some tests, dialing in a third or half stop of exposure compensation for some of them, and see what happens.

 

<p>Oh, if only the 10D had separate channel histograms....

[fastshutter]

"If so, my 10D red channel goes a little nonlinear near the top of the histogram and gets saturated about a half stop sooner than the green channel."

 

This is what is happing to me on all my shots. maybe the example I put up wasnt the best. here is another shot I did same lighting and underexpoused a half stop. the red channel jumps out again. I have the white balance set to the 5600k lights I'm using.<div></div>

[peter_lange]

I found it somehow interesting to see that the same "teething problem" seems to survive from one device generation to the next - independent from the brand.

 

Let's ignore the 5600K for a moment. At any light conditions - being not perfectly controlled - it's hard to state what the color temperature was and what the right R:B ratio should be. Your red channel may be ahead, but my best guess is that your green channel G lays behind. That's not the same.

 

Just for a simple test: Take a white sheet of printer paper. Expose it in a way to get RGB numers in the range of 200 to 240. Use the ACR sliders for CT and Tint to get R=G=B.

The Tint is a SYSTEMATIC ERROR, idependet from CT (R:B). I would expect that you can leave this Tint setting for all future shots (studio or outside).

Regarding CT (R:B) I tend to trust what my camera sees, or I make an idividual decision on a image to image basis. Studio is not my core competence, but you might wish to stay with the CT setting obtained above. This changes your color temperatures from 5600K to D65 in Adobe RGB, however, while passing "through" the printer profile it is reset to a warm whitepoint anyway.

 

Just one final remark - trust that you are aware of - but with a portriat you will always find a dominant red channel. Skin tones are red hues.

 

Peter

 

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