rgb to cmyk conversions with photoshop 5.5

[deano25]

Is there a simple way to get good results, when converting rgb files to cmyk, without being a color expert/mathemetician/ or taking a complex color theory course. I only need to do this once in a while, most of my work is printed in RGB. SO far my results have been bad. The proofs from my espon look fine but when the magazine ad comes out it looks flat and unsaturated.
PLEASE HELP!

[Erik Heyninck]

The problem is that the possible hues in CMYK are far more limited then those in RGB, although CMYK does have some hues that cannot be reproduced in RGB.

As for printing in RGB: I don't think you ever did so,as every printer works with black and the three colours inks. Some new printers use six colours to expand towards the RGB (minitor) hues, but they are very expensive.

I'm convinced that Photoshop will offer you a possibility to see on your monitor what the image will look like in CMYJ, and also a warning that you're out of gamut.

Did you consider consulting the help files?

If you don't work against time, time often works for you.

[deano25]

I think you've misunderstood me.
I do most of my printing on my epson printer from rgb. The problem is when I need to have some thing printed at a professional printing lab. They require cmyk files.

[Beth]

this is not a simple task. Especially if you are on a windows machine.

Ist off for anything going to print, you should have your monitor gama set to 1.8 and not the default 2.2 of windows. This should make a big difference in how things appear on screen.

You should calibrate you monitor. There is the photoshop method that you can follow. (pretty easy as I recall) But you are best to calibrate your monitor instead of just photoshop. Check out your video card info (see what is in the control panels) and see if there is any controls for calibrating. If not check the OS. Win 2000 is supposed to have better colour management. There are also third party utilities for this.

I have an Epson 3000 and when I send RGB to it I use one driver and when I send CMYK, I use another. But most of the Epson printers dont work like this (I think). Mine is a so called professional model and comes with postscript. Most do not. Anyway, this may also need to be calibrated.

Ink setup in photoshop: Doing a conversion from RGB to CMYK, PS looks at how you have your prefs set in the colour settings. And the default settings are kind of muddy. As I remember, I followed the guidelines set by Daniel Margulis for photoshop 5 and 5.5. I did alot of press work and the colour worked pretty good. Here is what I did. Be sure your monitor gama is set to 1.8. Then change the following under the CMYK setup. Change GCR to light, set black ink limit to 85. Overall dotgain to 18% but you may want to increase this if your seps are too dark. After you change the overall dot gain, then change the dot gain from standard to curves. In each of the CMYK inks, enter the following numbers at the 50% point. For M and C 68. For K 72 and Y 66. (this should result in better seperations with more accurate ink dot gain settings)

Now when you preview images in RGB you should be getting a more accurate representation on the monitor. When you convert to CMYK, PS will use the settings we just entered (and others) to create the CMYK image.

Also, the default setting in PS5 (and I think 5.5) was to embed a colour profile in all files. This is not a good thing....especially if you dont know what you are doing. So turn off the embedding of profiles until you know that your systems colour calibration is accurate.

The next colour print job you are doing, try getting the colour key and a final printout of your job and compare them to your colour on your monitor. THis is an ongoing thing. The phosphors in your monitors change with time and you will need to check your callibration.

best of luck,
Beth

PS: check the website for your monitor company and see if they have any info on colour calibrating. You might also be able to phone tech support for help. Also, as I said, check out info for your video card too. Some colour calibration tools.