I thought it would be easy, but it doesn't seem to work as I expect. maybe my expectations are wrong...
I have a very simple image, 32-bit CMYK which is just black & white. I want to change all the black to Cyan. Should be easy, I just use rectangle mask to mark out the area I want then go to "Adjust->Replace Colors..." and it comes up with a dialog. So far so good.
I use the color picker to select black as the source I want to change, then I choose the color to change to, either with color picker or manually mixing it to pure Cyan. The colour does change, to something blue-ish or cyan-ish, but not what I specified. Same deal if I try with Magenta. It's close, but not quite.
If I just fill with Cyan, it does indeed come out the right color.
Is there any tutorial on how this is supposed to be used?
IBall said:The colour does change, to something blue-ish or cyan-ish, but not what I specified.
It sounds to me as if your colour management settings are having an unwanted effect here.
I'm testing it here with colour management off and I am getting pure cyan. But I'm using X4, which might not work completely the same as X5.
Hmmm... maybe my limited understanding of color management is wrong, but when I ask for Cyan (e.g. CMYK = 100,0,0,0), I should always get CMYK = 100,0,0,0 regardless of what profile is active or if I have colour management on or off. The difference is what it actually looks like, no?
When I switch between different profiles in the document, for example, picking Photoshop 5 Default CMYK, on my monitor, the white looks slightly blue-ish. However, the color picker still indicates the correct color. White is CMYK = 0,0,0,0 despite the blue-ish tint. The problem is using the Replace Color function, it doesn't do this. The actual color replaced isn't correct. If I specify CMYK = 100,0,0,0 as the replacement color I instead get something (for example) like CMYK=77,23,0,0
Even if it were color management stuff kicking in, should that happen when I do a normal flood fill? That behaves as I expect, when I ask for CMYK=100,0,0,0 I actually do get that color (regardless of what it appears like on my monitor).
I think X5 doesn't have CM off mode, the best I can find is the simulate CMYK off or emulate X4 mode and neither of these help.
Offhand, I can't think why any colour management model should prevent you setting specific CMYK colours to a CMYK image.
It looks like a bug rather than intentional behaviour. And I've just checked -- X4 has exactly the same problem when colour management is on.
Bummer. I'm going to have to chalk it up as a bug.
If I change the image to RGB, the Replace Color feature behaves exactly as I expect it to. It's just in CMYK. It almost seems like when working in CMYK for this feature, it tries to map back to RGB (using some color management) then does the replacement, then maps it back to CMYK (again some color management) which really screws things up.
To give Corel credit, I tried pulling the same trick in Photoshop CS5. The documentation is even worse and the feature is even less user friendly. I found a bunch of tutorials on-line describing this step-by-step (in older versions), but no joy here either. It doesn't matter if I import a regular CMYK TIFF or start a new drawing from scratch, it just doesn't seem happy.
It's not me, I know I'm using it properly. I pulled in a JPG into CS5 and here the Replace Color option again works as I expect. Duplicate the task in Photo-Paint, yup, also works as expected. When it is working, I'll say CS5's functionality is a lot more flexible by being able to select multiple colors to replace.