Computer Graphics with Photoshop - Adjusting Printer CMYK settings

Author

Adjusting Printer CMYK settings

bstansbury@sbcglobal.net

2006-03-23, 3:14 am

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

Mike Russell

2006-03-23, 6:14 am

<bstansbury@sbcglobal.net> wrote in message
news:1143094187.642583.189990@u72g2000cwu.googlegroups.com...
> 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/downloa..._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

tacit

2006-03-23, 6:14 pm

In article <1143094187.642583.189990@u72g2000cwu.googlegroups.com>,
bstansbury@sbcglobal.net wrote:

> 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.

Ain't gonna work, sorry.

Your printer prints in a variant of CMYK, but the printer driver only
accepts RGB data. If you print a CMYK image, it is converted to RGB,
then back to CMYK, by the driver software. You can't print CMYK to your
inkjet printer directly.

Also, consumer inkjets do not use standard CMYK inks. Instead, they use
modified inks (in particular, the cyan ink is bluer than pure cyan),
because pure CMYK is not very good at reproducing rich blue colors, and
the printer manufacturers feel that consumers are more pleased when they
see richer blues. So to get this, they don't use pure CMYK.

--
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all at http://www.xeromag.com/franklin.html
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Bill Hilton

2006-03-23, 6:14 pm

>bstansb...@sbcglobal.net writes ...
>
> 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

In addition to the problems mentioned by Mike and Tacit you'll quickly
find that "pure" colors are very far out of gamut for your printer.

John McWilliams

2006-03-23, 6:14 pm

tacit wrote:
> In article <1143094187.642583.189990@u72g2000cwu.googlegroups.com>,
> bstansbury@sbcglobal.net wrote:
>
>
>
> Ain't gonna work, sorry.
>
> Your printer prints in a variant of CMYK, but the printer driver only
> accepts RGB data. If you print a CMYK image, it is converted to RGB,
> then back to CMYK, by the driver software. You can't print CMYK to your
> inkjet printer directly.
>
> Also, consumer inkjets do not use standard CMYK inks. Instead, they use
> modified inks (in particular, the cyan ink is bluer than pure cyan),
> because pure CMYK is not very good at reproducing rich blue colors, and
> the printer manufacturers feel that consumers are more pleased when they
> see richer blues. So to get this, they don't use pure CMYK.
>

Combined with what Mike also posted, is it correct to say that in theory
what the OP wanted to do is possible, but that in practice there a lots
of factors that preclude this?

And, Mike, thanks for pointing to the test strip you made. I recall now
I downloaded that sometime ago, and took your course, in which I learned
a lot. Do have one question, tho: what do the OoF images along the strip
do?

--
John McWilliams

Mike Russell

2006-03-23, 6:14 pm

"John McWilliams" <jpmcw@comcast.net> wrote in message
news:q9edna_ljezoV7_ZRVn-tQ@comcast.com...
....
> Combined with what Mike also posted, is it correct to say that in theory
> what the OP wanted to do is possible, but that in practice there a lots of
> factors that preclude this?
>
> And, Mike, thanks for pointing to the test strip you made. I recall now I
> downloaded that sometime ago, and took your course, in which I learned a
> lot. Do have one question, tho: what do the OoF images along the strip do?

Hi John, Yes, I remember you! The OOF images are a variety of skin tones.

I'm a big fan of controlling images based on what I can see. Since people
are instinctively very sensitive to skin tones, these are handy as a quick
sanity check that the colors are all there, and relatively close to what
they should be. The important thing, though is the gray step wedge.

Having visited any number of friends with enormous piles of test images, I'm
also rather pleased with the ability to get 10 or so strips from each sheet
of paper.
--
Mike Russell
www.curvemeister.com