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Skin Tone color corrections, CYMK or RGB?

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  #1  
Old 02-11-2005, 11:49 AM
jayk2 jayk2 is offline
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Skin Tone color corrections, CYMK or RGB?

Hello all,

I'm very interested in skin tone correction and have a question. Almost every tutorial and book says to edit skin tones using cymk and basically make sure the yellow reads 3-5% higher then Magenta. I work in Adobe RGB and wondering if that percentage rule applies only to CYMK? or can I apply that rule when using RGB?

I'm posting a few images from a shoot I had a few weeks ago and color corrected in RGB using the CYMK rules. Just wondering if I can get some ideas as to if the yellow percentage works in RGB, or if there's a different way I should be doing it? My work flow is unsharp mask, Levels adjustment, slective color adjustment (yellow and red only) and whatever color the backdrop is.

Thanks
Jay

http://www.tossthebox.com/clients/images/IMG_0228.jpg

http://www.tossthebox.com/clients/images/IMG_0368.jpg

http://www.tossthebox.com/clients/images/IMG_0433.jpg
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  #2  
Old 02-11-2005, 01:29 PM
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I myself haven't a clue how to adjust skin tones using RGB. I've always converted to CMYK to do my skin correction and then back to RGB. There seems to be a lot more information on CMYK skin correction. Although I haven't noticed anything, I'm wondering if converting back and forth may introduce other subtle problems. The tones you acheived are spot on. I never considered using Selective Colors to do my correction. I'll have to give it a try. Can I ask why you adjust yellow and red as opposed to magenta/yellow/cyan and black?

Cheers
Dave
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  #3  
Old 02-11-2005, 01:52 PM
jayk2 jayk2 is offline
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Thanks for the reply Duv,

I also wonder the same, if I'll loose some quality in the convert and working back and forth?

I was once told that to get proper skin tones in "white" (for lack of a better term) people, it's yellow and red. I was told by another photogrpaher that he never adjusts for skin tones, just boots up the saturation by +15 or so.

I'm going to try and do a correction via the cmyk,

I'm scared lol.
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  #4  
Old 02-11-2005, 02:16 PM
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Hope you show your results.

Dave
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  #5  
Old 02-11-2005, 02:48 PM
jayk2 jayk2 is offline
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Here's a quick mock up of what I did. According to the cymk, this image was fine to start with. I was under the assumption that pretty much every portrait image needed to be retouched?!

http://tossthebox.com/clients/cmyk.jpg

When I get a chance, I'll pick a better image
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  #6  
Old 02-12-2005, 03:19 AM
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v.bampton v.bampton is offline
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We have a portrait and wedding studio, and whilst there are benefits to correcting in CMYK, we do almost all of our adjustments in RGB. Because of the difference in the size of the gamut, converting to CMYK and then back to AdobeRGB for our lab does affect some of the colours. If you're concerned about watching the CMYK numbers, then make sure your info palette will show RGB and CMYK, and the same rules will apply. There's also a speed factor - I don't have time to convert everything back and forth when I'm working on hundreds of images a week.

I've got perfectly good results using RGB, sometimes boosting the saturation, more often just adjusting the red and yellow slightly (highlights and slight midtones in levels or curves) to give a healthy warm glow. Most of it I have set up as actions, so whilst we do retouch every image we sell, it's usually only minor tweaks that we need to do manually.
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  #7  
Old 02-12-2005, 03:10 PM
jayk2 jayk2 is offline
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Quote:
Originally Posted by v.bampton
We have a portrait and wedding studio, and whilst there are benefits to correcting in CMYK, we do almost all of our adjustments in RGB. Because of the difference in the size of the gamut, converting to CMYK and then back to AdobeRGB for our lab does affect some of the colours. If you're concerned about watching the CMYK numbers, then make sure your info palette will show RGB and CMYK, and the same rules will apply. There's also a speed factor - I don't have time to convert everything back and forth when I'm working on hundreds of images a week.

I've got perfectly good results using RGB, sometimes boosting the saturation, more often just adjusting the red and yellow slightly (highlights and slight midtones in levels or curves) to give a healthy warm glow. Most of it I have set up as actions, so whilst we do retouch every image we sell, it's usually only minor tweaks that we need to do manually.
Thanks bampton,

Thats what I was wondering. When I did the above pics, I was going by the cymk values but adjusting in rgb. I wasnt sure if the rules applied to rgb as they did for cymk. So for now, I'll just continue adjusting

thanks all
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  #8  
Old 02-13-2005, 08:04 AM
edgework edgework is offline
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Quote:
Originally Posted by jayk2
Thanks bampton,

Thats what I was wondering. When I did the above pics, I was going by the cymk values but adjusting in rgb. I wasnt sure if the rules applied to rgb as they did for cymk. So for now, I'll just continue adjusting

thanks all
I do the same thing when I have to work in RGB. The rules are roughly similar, but keep in mind that Photoshop simulates the qualities of light in RGB, and ink on paper with CMYK. One significant difference is that in CMYK, applying a curve to any channel will affect both color and lightness in a very different way than with RGB. A rule of thumb is that you use the individual channel curves in RGB to adjust color, and you use the master curve to adjust contrast. Because Red, Green and Blue are all equal in intensity (equal values combine to produce dead neutral) the master curve can be used effectively to make lightness moves without altering the hue and saturation (although the lightness channel in lab mode is far more efficient). In CMYK, since cyan is such a crappy ink, it requires about 10% more than Magenta and Yellow to balance the other two and produce neutral. Using the master curve in CMYK is very dangerous, unless you are using it in luminosity mode.

I was trained to use CURVES, and CURVES only, (and only in CMYK) since most of the other adjustment tools are more or less subsets of what curves are capable of doing. However, I've found that using selective color in the way previously mentioned, is a great quick fix. If, for example, a face has yellow highlights and hot red shadows, pulling magenta and adding yellow to the reds, and pulling yellow and adding magenta to the yellows brings the tones into balance, albeit a flat kind of balance.

Another trick for skin (this is for CMYK corrections): I've never found a face that cannot be improved by making a contrast move to the magenta channel in luminosity mode. Flat skin tones are almost always the fault of the magenta plate, and even if the numbers are within a realistic range, the lack of contrast can make the skin appear too hot overall. Heightening the contrast in magenta, but keeping it in luminosity mode can open up detail in an instant, without messing up the color.

As for converting back and forth, the areas of RGB that extend beyond CMYK are far more extensive in the Greens and blues. The truth is, any colors in RGB that are outside the CMYK gamut aren't going to look all that appropriate in skin tones anyway--greens, blues, hot reds and day-glo oranges. If realism is the desired goal, moving into CMYK before correcting the color will weed out a lot of unrealistic tones. But if intensity and bright colors are the visual goal, and the target is RGB output, or the WEB, keep it in RGB.

One problem with CMYK that is non-existent in RGB is ink density. Because there is a limit to the quantity of ink a press can handle without turning the result into mud, the CMY channels will usually flatten out to a single tone in the shadow range, shifting the detail information into the black plate. This can be a problem if you have shadows that carry a cast, either hot or cool. Moving an image into CMYK will usually turn the dark areas neutral, which will be a problem if the mood of the original art called for overall warmth or coolness. I often use selective color for these situations too, pulling cyan from black and adding magenta and yellow, or the other way around to cool them down. Pay attention to the darkest shadows as well as dark hair: it's easy for rich brunettes to become dingy blacks in the translation.
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  #9  
Old 02-13-2005, 09:15 AM
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Good stuff here from V. Bampton and Edgework. I especially like the tip on boosting contrast luminosity in the magenta channel.
I hope everyone understands that Edgework is NOT suggesting a 10% higher Cyan value than Magenta and Yellow for skin tones.

Cheers
Dave
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  #10  
Old 02-13-2005, 03:49 PM
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Flora Flora is offline
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Hi everybody,

I'd like to join Dave in thanking v.bampton and edgework for the great explanations on this topic!
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  #11  
Old 02-15-2005, 11:07 PM
charlotte charlotte is offline
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Skin tones and adjusting them . Sometimes I wonder if I will ever master it. I have no understanding of where to start. Usually I just use levels. But I know there are other ways and that you can watch the numbers in the info but I have no clue about all that. Would love to see more info on this topic . Maybe even a long ,slowwww, : ) in depth tutorial for us over 40 brains . I appreciate the info so far .Will read and reread it many many times . : /
Charlotte
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  #12  
Old 02-16-2005, 01:14 AM
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v.bampton v.bampton is offline
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Ok, nice and easy...

If you're working on a decently exposed image, then you shouldn't have a problem. Find the blackest point in the image (that's supposed to be black), and watch the info pallette as you adjust. Move the end point of your levels or curves individual channels that black point reads a neutral number, (ie. R5, G5, B5). The move to the highlights, find the lightest point that's supposed to be white (not a specular highlight) and make it, say R245, G245, B245. If you haven't got a true white and black point in the image then it's a bit more complicated, so practise on ones that do.

Once you've got a neutral white and black point, you're mostly corrected. See if there is anything else that's supposed to be a neutral midtone - maybe some ones suit, or church stonework. Beware that if the point you pick isn't actually supposed to be neutral, then your midtone colours will be thrown off. Again you're trying to get a neutral - where your R, G, and B number are all about the same.

Once your image looks (and is by the numbers) neutral, you can adjust for taste. I tend to add an additional adjustment layer on top for my personal adjustments, leaving the neutral adjustments as they are. That way if I don't like my adjustments I can always go back to neutral without having to start again.

I tend to add red and yellow to the highlights and midtones. Something like R 0, 1.05, 250, 0, 255. G 0, 1.0, 255, 0, 255. B 0, 0.93, 255, 0, 250. It's not exactly neutral, but adds a nice warm glow to the skin which for portraits is ideal.

Hope that helps a bit.
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  #13  
Old 02-20-2005, 08:38 AM
john_opitz john_opitz is offline
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If you want to go back and forth, from rgb to cmy and back to rgb again for editing. Try this profile. You can go back and forth with no/min. loss in gamut.
Caution: this profile is not for cmyk printing (output). This profile exceeds the TIL for printing.

Wide gamut cmyk profile
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  #14  
Old 02-20-2005, 11:31 PM
charlotte charlotte is offline
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Interesting v.bampton. Thanks for posting.
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  #15  
Old 03-07-2005, 07:04 AM
hpycmpr hpycmpr is offline
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Good thread

This is a great thread since it touches on a few topics I'm interested in. I'll try to respond separately on each topic to avoid confusion.

To provide some context to my posts, here's my PS experience so far. I've been teaching myself PS for two years, relying on books and tutorials. My favorite authors include Eismann, Haynes and Margulis. I rely heavily upon curves and by the numbers for my corrections, and not so much upon masks, painting, and channel mixing, all of which I'm now trying to get better at. So far I have been correcting my landscape photos from film scans, and now I'm beginning to correct portraits.
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