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I'm try to create a master test image in PS 6 in CMYK color control such that I can then print out those test images and use them to further adjust the custom settings in my Canon i560 printer. I need to do this because all of the Color test charts that I have found on the internet and printed on my printer come out with some colors wrong. This approach basically shuts down any usage if ICM. I'm not trying to match colors that appear on my monitor, even though I have the gamma and the color balance set rather good. What I need to do is make sure that my printer is producing as good as possible a color match to the basic Cyan, Magenta, Yellow colors.

I believe what I need is a pre-printed color chart that has Cyan, Magenta, and Yellow on it. Then I can use PS to print color bars that are pure Cyan, Magenta, Yellow, and also mixtures that will produce true RGB colors. I can then run as many test prints as I need to get the CMYK to match the control sample.

I have tried this by printing test charts like the one Tiff image provided at www.digitaldog.net
but it is very difficult to understand the individual reaction of CMYK to each color. Colors are not as bad as Grayscale which also interacts with any change in CMYK.

In theroy you should be albe to adjust any given set of ink jet printer nozzles, with a given combination of ink and paper, such that if adjusted correctly, equal quanities of C, M, & Y, will produce "Black". Also, equal amounts of Cyan and Magenta will produce "Blue", and so on for Green, and Red. This is what I'm trying to do.
Hope someone has some ideas. Thanks

You're trying to do the same thing I did when I got my first inkjet printer years ago. Unfortunately it won't work because your inkjet printer is being used as an RGB device, not a CMYK one. This means that your CMYK image is being translated to RGB before being printed, and the printer driver is reseparating the image back to CMYK before printing.

The easiest way to verify this is to start with a white image, create something gray in the K channel, and print it. You'll see that it consists of a mixture of CMYK dots, and not pure black.

As a further theoretical point, equal amounts of CMY do not produce black, but a muddy brown color. This happens because the cyan ink is "weaker" than the other inks, meaning that proportionally more cyan is required to produce a neutral gray color. A good black is not possible with the CMY inks, and this is one reason for the addition of the K to CMYK.

But all is not lost. Concentrate on printing a good neutral gradient and the rest will take care of itself. You may get satisfactory results by adjusting the individual colors in your driver in a systematic way.

1) Start by calibrating your screen with Adobe Gamma. If you have a screen calibration device you may save some work here, but this is not necessary, and IMHO it is beneficial to do this manually as a starting point to get a good sense of color adjustment.

2) Print a neutral gray step wedge. It's surprisingly hard to create such a gradient in Photoshop, mainly because the default gradient settings add noise, and are non-linear. I have provided such a gradient, with instructions, here:
http://www.curvemeister.com/downloads/TestStrip/digital_test _strip.htm

3) The step strip page has instructions for systematically adjusting your colors to get the test strip as neutral as possible. The object is to get the test strip to appear neutral throughout, and to have the overall darkness match what you see on your screen.

4) Once you're done with that, print some more complex images and see how well your colors match. Keep in mind that some colors, including deep saturated blues, will never look as quite as good on your printed output as they do on the screen.

BTW, although I would urge you not to spend a lot of time trying to get individual colors to match, you can certainly make your own images with known percentages of CMY and K. There is also a well-known image, Ole no Moire, that used to be shipped with Photoshop. It is a rather pleasant four channel jpeg image with various mixtures of CMYK on it.
http://www.rcs.plc.uk/downloads/Ole%20No%20Moire.tif
--
Mike Russell
www.curvemeister.com

bstansbury

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