: I think you may just be running into a problem with the two color models. A CMYK image is 32bit because there are four separate color channels to represent. The RGB model only has three

I think you may just be running into a problem with the two color models. A CMYK image is 32bit because there are four separate color channels to represent. The RGB model only has three color channels to represent. When you convert from a 32bit CMYK image to an RGB image, the two common options are 16bit or 8bit, as outside of floating-point HDR images (which is an unlikely option here), there really aren't any 32bit integer RGB image formats (excluding those with an alpha channel of course, which would be RGBA.)

Its difficult to explain this, other than to just say that there is no "direct" conversion from a four-channel CMYK imate into a four-channel RGB image. The conversion is a fairly complex mathematical process involving ICM that is translating colors from one color model (the subtractive CMYK model) to another color model (the additive RGB model). I can't really say exactly how much distinct color information your CMYK image may contain, however I would be doubtful that it contains as much color accuracy as a 16bit RGB image can represent. You are probably safe to convert into an 8bit RGB image, however if you really want to make sure you preserve the maximum amount of color accuracy, I would convert into 16bit RGB.

There is no 32bit integer RGB format I know of that you can convert into, or at least, not one that Photoshop supports. HDR images are 32bit floating point, however there is no direct translation from a CMYK integer format into an HDR floating point format. Even if there was, a 32fbit HDR image can portray a range of tones and colors far beyond anything reproducible in CMYK print, and you might end up with some undesirable artifacts if you managed to find a way to convert between the two.

As for the color differences, you will need to make sure that the images are assigned the appropriate color profiles. ICM is involved in conversions between color models, so making sure that your source image has a valid and appropriate color profile assigned to it that properly maps the colors it contains will be important in preserving color information when converting to RGB. It is highly unlikely that you will be able to get 100% accurate representation of the CMYK colors in RGB due to significant differences in those two color models, and the differences in the color profiles assigned to both images. There will most likely be some color shift between the two. You may have to do some pre- and post-processing in both images to set proper white/black points, adjust contrast and saturation in RGB, etc. to get a correct final image out of the conversion.

10% popularity Vote Up Vote Down