setting CMYK values

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DougJ
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Joined: Fri May 12, 2006 4:39 am

Postby DougJ » Tue Oct 04, 2011 6:45 am

Hi folks,

When correcting skin colour I tend to follow Lee Varis' approach of adjusting the RGB values in a CS5 curve adjustment layer to nudge the CMY values in to their correct relationships. 

However, on some occasions, I change my colour mode (for the image) from RGB to CMYK so that I can enter specific output values for each of the C, M, and Y colours.  Then I revert to RGB and continue.

Tonight a neuron fired :) and I thought, gosh I should just invoke Curvemeister, work in CMYK while entering my specific output values, save and continue working in CS5 in RGB. 

My problem is that I don't see where (or how) to enter specific %age values for the C, M, and Y colours.

If someone can show me the way I'd be grateful.

Ciao,

Doug


-default
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Joined: Thu Mar 26, 2015 1:53 am

Postby -default » Tue Oct 04, 2011 10:19 am

Click on the cmyk curve, and type the desired value into the edit box that appears on each of the CMY curves.  Or use one of the built-in skin tone pins, or a hue pin that is set to your desired CMY values, and drag that onto the desired area of the image .

Let me know how it goes!

Mike

DougJ
Posts: 17
Joined: Fri May 12, 2006 4:39 am

Postby DougJ » Tue Oct 04, 2011 4:27 pm

I now see that--sorry I couldn't see that last night. :(

Two related questions:

1.  I start in RAW and then export to and work in RGB ProPhoto.  In CS5 I changed mode to CMYK, used the CS5 CMYK curves to enter my desired output values, then changed back to RGB--which I'm now sensing is not a good thing to do.  Anyway, that change back to RGB put me into sRGB and that's not where I want to be.  Am I missing something or is this because the CMYK gamut is so much smaller than the ProPhoto?

2.  I am thinking that when I use CM to adjust CMYK values directly, that I never leave my ProPhoto colour space.  However, the resulting colour (and I'm working with a colour managed workflow) is not close to what I get when using the mode change in CS5.  What version of CMYK should I be using?

May be this looking to adjust the CMYK values directly is the wrong way to work and I should work harder at getting to my Y>=M>C (roughly) for skin by adjusting the individual RGB curves.

Again, TIA for any suggestions you care to make--I do value what you have to say.

Ciao,

Doug

PS: did you see my other post on latest "approved" version of CM?

-default
Posts: 1916
Joined: Thu Mar 26, 2015 1:53 am

Postby -default » Wed Oct 05, 2011 12:19 am

Hi Doug,

No problem - I always enjoy answering questions.

1. It sounds like you have your default RGB space set to sRGB.  Type ctrl-shift-K to check, and adjust this.  You are correct that CMYK is a much smaller gamut that ProPhoto.  Curvemeister, however, uses wgCMYK, which is a wide gamut version of CMYK.

2. Curvmeister uses wgCMYK, not CMYK.  The color "weights" of the CMY channels are more equal than in CMYK, where, for example the Cyan ink is weaker (requires proportionally more) than the other channels.

You can use wgCMYK, which is essentially a repackaged RGB, to adjust your ProPhoto images with no gamut penalty.  That was actually the original inspiration for Curvemeister: to encourage use of CMYK for people who did not want to go through the conversion "loss".

I do have Lee Varis's "Skin" book, if that is what you are referencing.  The ratios of CMY that he (as well as Dan Margulis) recommend are really specifying a hue and saturation value.  Here's another way to go about it and get a similar result: you'll get a good skin tone if you use the hue clock - point just to the right of the R at the top of the clock, set saturation so that the hand is just over half the distance to the outside edge of the clock, and you'll get a good average skin tone.

Mike

-default
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Joined: Thu Mar 26, 2015 1:53 am

Postby -default » Wed Oct 05, 2011 12:19 am

The current version of Curvemeister is 3.3.6, available on the downloads area of the forum. - Mike

DougJ
Posts: 17
Joined: Fri May 12, 2006 4:39 am

Postby DougJ » Wed Oct 05, 2011 7:33 am

Hi Mike,

Smart man, my friend: I did have the default working space set to sRGB--it had not been causing me a problem since in going from ACR to CS5 I have that set to open my file in 16-bit ProPhoto and I don't usually change colour spaces (I do use Margulis' false profiles from time to time, but that is by an assign profile rather than convert profile, IIRC).

Once I reset the default RGB working space to ProPhoto in the colour settings GUI my RGB to Adobe CS5 default CMYK back to RGB worked well, meaning I was satisfied with the print.  Truth to tell, it worked almost as well as the result of my renewed efforts to adjust the skin tones by working in RGB colour space with RGB-curves. 

I did also try adjusting skin tones using WGCMYK within CM; unfortunately, I have to say my technique must be faulty for that gave quite unsatisfactory results--the resulting image was too light, and while I suppose I could have used levels to darken the mid-tones, I did not try that.

So I tried the mode change approach selecting WGCMYK as the destination CMYK profile, adjusting and then reverting to RGB--here the result was very close to that I obtained using CM.  But, as I've said earlier, if I used the Adobe 5 default CMYK in the mode change approach, I got results I found satisfactory.

I tried the "hue clock" approach, and while that did improve skin tones, it did nasty things to the blue jacket my wife is wearing--which I suppose I could have masked out, but, but, the adjustment in RGB of the most offending skin tone did not damage her jacket.

As for Varis, I have both Skin and Skin 2 and have them handy whenever I'm dealing with an image that has skin.  On page 104 of Skin 2 he sets down the rule: C= 0.25 of Y, and M and Y almost equal, but Y>M.  Continuing from page 104, his adjustments are all done with curves; it is not until page 165 that he uses Hue/Sat to repair colour--a "trick" I've seen Versace demonstrate. 

And finally, I downloaded and installed V3.3.5 of CM and it is working as advertised with my XP SP3 operating system.

My thanks for your assistance.

Ciao,

Doug




-default
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Joined: Thu Mar 26, 2015 1:53 am

Postby -default » Wed Oct 05, 2011 8:23 am

Hi Doug,

Super!  I'm glad you have things more or less worked out.  One item of potential confusion - the WGCMYK profile is a different color space than the wgCMYK that is built into Curvemeister.  The overlap of names resulted when I wanted to retain the name wgCMYK for the "true" wide gamut space supported by curvemeister.

Mike

ggroess
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Postby ggroess » Wed Oct 05, 2011 11:08 am

Doug,
If you use Curvemeister and CMYK make sure you have the correct GCR setting for the work you are doing.  If you have the GCR set too far to the light side your images may have a different "look" than if you use Max Black. 
GCR setting is in the bottom of the CMYK window in CM.

Greg

DougJ
Posts: 17
Joined: Fri May 12, 2006 4:39 am

Postby DougJ » Fri Oct 07, 2011 7:45 am

Hi Greg,

Thanks for pointing that out to me.  Adjusting the black as you suggest does improve the image, and resetting the BP makes it even better--yeah but, not as good as hard work with the RGB curves.

And Mike or Greg, if wgCMYK.icc (note the lower case) is the CM icc file, where can I find it.  I do have a WGCMYK.icm file in my windows folder but I am assuming from Mike's post that is not as good a colour space for making CMYK adjustments and then returning to RGB.

Again,

Thanks for your continuing assistance.

Doug


ggroess
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Postby ggroess » Fri Oct 07, 2011 12:35 pm

Doug,
I'll check with Mike but I think it's inside of the CM program itself.  CM converts on the fly and outputs back to the native space...I was not able to find an ICC on my system either.

Greg


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