CMYK grayscale


Well-known member
I have a job that has large areas of black and I have problems printing large solids of black (hickies etc). Generally I try to boost the black with CMY (50C, 45M, 40Y and 100K). Other times I convert the black to more of a photoshop black (75C, 68M, 67Y, 90K). Running the black at 90% makes life easier with regards to hickies.

My issue right now is I have a job that has graduated grayscale screens that I want to convert to CMYK tints. The tint goes from 100% to 60% K and I wanted to make it out of CMYK using primarily black but still some CMY so that I do not have to run my K at 100%. Any thoughts what some starting percentages may be. Of importance though is maintaining grey balanced tone without color casts. There are also some surrounding 10%K tints so I am not sure if I would leave as is or also convert to CMYK to more closely match the other boosted area.

Is there any kind of formula that could be used. I know it is probably pretty specific to press conditions (whether printing conditions are gray balanced or not) but just looking for a starting point.

First, you'll need an ICC profile that has maximum GCR and a full range K. For our purposes, we'll call this "MaxGCR.icc"

Open Photoshop and set up your Color Settings preferences to the following:

CMYK Working Space Profile: "MaxGCR.icc"
*Gray Working Space Profile: "Black Ink - MaxGCR.icc"

Save this as a new custom color setting and open a gray step wedge. Don Hutcheson's "LAB Ramps" is good for this.

Open the info pallete and set it for Grayscale on the left and CMYK on the right. Move your cursor/eyedropper across the gray step wedge until you find the "black ink" grayscale value you want to convert. When you find that, look at the CMYK values that it's giving you....that will be the equivalent CMYK values to match that K tone. Another way would be to open Photoshop's Color Picker and type in the K% (only) value, leaving the C, M and Y at 0%....note the L* (in Lab) value above re-type that L* value (a*, b* should be 0) and note the new CMYK value.

Here's an example for 50% K:
50%K = L*63
L*63 = 40K 11C 9M 9Y re-entering the L* value gives you the new "separated" values based on the "MaxGCR.icc" profile.

* To load a CMYK profile as a "Grayscale" profile, open the pop-up menu next to Gray in your color settings and select "Load Gray"...navigate to your "MaxGCR.icc" profile and select should now say "Black Ink - MaxGCR.icc".

If you'd like a couple of profiles with VERY aggressive GCR, just contact me off-list.

Hi ?
You shouldnt get hickies if press is set up,and stock has clean edges.When setting up press run your
colours as C M K Y .You will find that you will get a better resault .
This colour sequence is a good way to print your black solids with CMY add. Some jobs you just have trouble with getting the resault the client wants. I have had to swop colours around to get that requied resault . It depends on the stock , on gloss stocks it works well you get a better trapping and the black solid prints smooth. Any hickies that are in the stock will be picked up in the C or M. It will also keep your greyscale open more with the K having less blankets to print on. Some times with a lot of ink on the sheet you get a slight movement from blanket to blanket with the wave of the stock , coursing a slight movement in the dot on the blanket . With the K being your main colour printing it second last will give you a good resault.
Are you talking about images?
If you are in Photoshop, you can select neutral areas, use a channel mixer adjustment layer to move all all tone to K only. Now set the opacity of that layer till you get the TAC you want. Usually it is enough to go around set this to 80% letting the CMY fill in the 20% remaining.
If you have greyscale images I'd leave them as grey TIF, or JPG amd colourise in InDesign with a Swatch of 90-100K and appropriate greybalance mix 15-30%.

This is how I would approach it, there are ofcourse many other ways.


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