You don’t.
CMYK is a smaller color space because it is ink on paper and is reflective.
I can’t believe that…I sent a file to a printer once and instructed them to convert my files to CMYK and to make sure they maintain the same color as is visible in the RGB mode….They did somehow? I wonder how they converted it and maintained the same color vibrancy? There’s gotta be a way.
As Buko says, CMYK doesn’t have as large a colour range as RGB. That’s reality.
It all depends on the range of colors in the specific file, and what CMYK device (or profile) it’s going to. Even though CMYK generally can’t reproduce the vibrancy of RGB, there are things you can do to maximize the apparent saturation and contrast. Things like being aware of the limitations and working with opposing colors to trick the eye into believing the colors are richer than they actually are. After that, you can always start adding spot color inks…
BRAD,
Ask the printer how they did that, it would be interesting for all of us to know. I agree with CyberN.
Brad,
Your original question asks about color space conversions and layer retention. In general, it blows up due to the simple fact that blending modes and color space difference interact differently between RGB and CMYK.
We are also assuming you are printing offset – which has a smaller color gamut as people have stated. A digital press has a larger gamut – so we may be giving you answers that are questionable because we don’t know in what context you are speaking to.
"and to make sure they maintain the same color as is visible in the RGB mode….They did somehow?"
This is a good way to approach a printer. If it were not possible to maintain the colors you wanted the printer would have let you know before printing the job. "Somehow?" is most likely because the colors you wanted to maintain were within the gamut of the output of the printer’s press. Other than that you are working with two different color models, one is additive and the other subtractive. The gamut for each is different because they each are presented by different media which manipulate light in a different way. Whether RGB or CMYK, each of those also fall far short of the visible spectrum.
Rule = Work within the bounds of the media you are using for output.
thanks for the feedback. The printer that I know did that for me was years ago and lost contact with them…They wouldn’t even know what I am referring to at this point. I wish PS had an option to click that would "retain colors visually" when converting…Not necessarily by color levels…since they always vary. I know for instance that when I convert a color in Quark Express’s color pallette from PMS to a CMYK in most cases it drastically changes the colors and I have to mess with the color levels to gain that same PMS color back…PS is doing something similar here and just wish there was something in the "back end" that would keep all colors consistent with what I’m "seeing" when I convert. And I guess it could know what I’m seeing by the color settings that are set for my PS and color monitor. Whatda ya think PS developers??
Its called colour management
"And I guess it could know what I’m seeing"
And therein lies the hitch. Go through the process of color correcting with several people in the room and you’ll find that it’s the guy who is paying for the job who gets it right.
Color perception is subjective. Color houses play it by the numbers and so does Photoshop, because it’s the scientific way and simply rules out varied perceptions of one same sample.
This is why we have Graphic Artists. Good one’s take into account that people perceive colors differently, even seeing differently at different times, and work past that to make their work communicate.
You need to do the opposite, in fact, simulate how the image will look when printed, using soft proofing. A google search on this term (soft proofing) will give you some good starting points.
Brad,
There’s only so much you can do before you bump up against the physics of the ink. Unless you’re using some weird inkset and/or spot colors, all of the standard offset inksets have a fairly limited gamut, and they’re all pretty much in the same ballpark with no huge surprises. Without spot or Hi-Fi colors, there’s not much any PS engineer can offer you.
"Changing from RGB to CMYK changes colors….."
The title of this thread is a statement of fact.
Brad,
Why don’t you post a small sample of the file in question.
