Lightroom Histogram and Red Channel Clipping in Photoshop
February 21st, 2011 by ariana
I received this question in my inbox from Kacey. With her permission, I’m posting it here in case this discussion helps anyone else!
I’ve been reading your tutorials about LR and PSE and I’ve found them so helpful! I have a question about the Camera Calibration Profile in LR. When I choose Camera Neutral and make changes to the histogram in LR it appears that no highlights are blown. My problem is that when I bring the same image into PSE thereafter the hisogram shows blown highlights. Do you have any idea why that would happen? Thanks for any advice or info you may have in advance. I’ve been working with PSE for about 1 1/2 years but I’ve only recently begun to work with LR so I’m a bit confused.
Thanks,Kacey
Kacey has hit on something that drives many of us who are used to working with the RGB 0-255 scale a bit bonkers in LR. There is no way to switch the read out from %s to actual numbers. Additionally, even though the LR histogram doesn’t LOOK like the red channel is getting clipped, but it is if you consider the definition of red channel clipping is anything over 240 in the red channel for print purposes (Anything over 240 is not considered “safe”, some people even define that as low as 230, but personally use 240 with my lab and haven’t had any problems. Those results will vary lab to lab though, so you’ll want to test those values for yourself.)
For example, check out the LR histogram in this image of Jasper:
The curve doesn’t even touch all the way to the right end of the histogram.. and yet, when we bring this image into photoshop and inspect the cheek on camera right with the info palette, we see that the reading in the red channel is 251, ie. clipped.
So, what can we do in LR to remedy this?
A couple of things.. first of all, you can switch the calibration from “Adobe Standard” to “Camera Neutral” which often sucks out enough red out to tame the red channel into submission. If that is still not enough, you can either use the recovery slider or decrease exposure overall and just keep in mind that your histogram generally cannot touch all the way to the right in LR and NOT clip the red channel.
Here is my histogram in LR after I decreased exposure a tad and also moved the recovery slider from 0 to 6:
Notice the extra space to the right side of the histogram. Also, take a look at the R %… it reads 93.3. You can’t see it on the screen shot, but I was hovering in the same cheek area that I sampled in Photoshop. If you compare this percentage with the percentage of R before I upped the recovery slider and brought the exposure down, you can see that it went down from 97ish% to 93ish %. I have found that you can use this as a general rule of thumb that any R% that approaches the mid to upper 90s is going to be clipped in PS. Keep it around the low 90s (always checking of course!) and you should be OK. Here is what it now reads in Photoshop:
One more word about the recovery slider: I prefer to use it sparingly and favor lowering overall exposure because overuse tends to suck all the “life” out of the image and also shifts the colors in a way that I don’t love.
This is a slightly oversimplified explanation, because there are also some colorspace issues that contribute to the problem, but I have found that the red channel numbers don’t change more than 1-2 points on the 0-255 scale depending on which colorspace you are working in (sRGB vs Adobe RGB for example) so I didn’t want to complicate my answer with that issue. But if you are interested in reading more about it, Damien has an excellent post about it here.
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I know I blow my red channel sometimes. I love to shoot slightly over-exposed. I have never been really big about checking my CMYK levels though. Thanks for posting the percentages. It is a great guide!
I know Lisa!! It would be super handy, I would die and go to heaven if we could get CMYK readouts for skintones!! The RGB% math is way too hard for me to translate in my head to CMYK:)
Great post – thanks! 93-94% makes sense as 240/255=94.1% – nice to have a rule of thumb to go by. I’ve never understood why LR doesn’t have the same info palette-type readouts as PS – CMYK values would also be really handy.