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View Full Version : CMYK for levels and curves?



edward saltau
06-01-2008, 08:12 PM
I've been wondering about this for a while. I keep hearing from a friend that CMYk is great for extra control on colours and contrast when doing levels and curves. After playing around with it on some surf shots i've found that i like it for shots that seem biased towards magenta or cyan.
But the best thing i've found about CMYK is the Black colour channel. In levels that black channel slide is awesome.
Anyone else got some knowledge on why there is actually a difference when using CMYK or anything i should be wary of using CMYK? should i be using it at all???

Robert Amoruso
06-03-2008, 08:44 AM
Edward,

Interesting observations I will investigate. Thanks for posting and I will get back to this post when I look into it.

Robert O'Toole
06-03-2008, 02:13 PM
Hey Edward
Having worked on more than a few post production projects for print I have spent a lot of time in CMYK.
CMYK is used in printing and is subtractive, the inks subtract brightness from white, RGB is the opposite.

The are problems with color reproduction when going from RGB to CMYK and back. Photoshop has proofing and clipping warnings for CMYK built in if you would like to see for yourself. I wouldnt bother and dont see any gains for working in CMYK except for one that you mentioned.
Since CMYK does have a separate black channel there are gains in detail and for sharpening. I also have experience with this, you can dupe the image, work on the black channel than copy it over to the orig RGB image. It really can help sometimes with images with large areas of textured blacks.

Working on the Black Channel is CMYK can work well in some suituations. I would never bother doing levels or curves in CMYK. For this LAB makes much more suited to this.

I have a black Channel tutorial that I was thinking of including in my new CD but I didnt think there would be any interest. It is a very esoteric technique.

Robert

Robert Amoruso
06-03-2008, 08:12 PM
Thanks Robert. I started to do some digging today and came up with similar suggestions as in your excellent explanation.

edward saltau
06-04-2008, 07:43 PM
thanks robert!
After reading your post and playing some more, i think i will use CMYK for exactly what you said - lots of textured blacks. I also like it when doing some black and white stuff too...