Batch Automation How to set a CMYK image for 2 colors printing

[erlebe]

Hello, In this CMYK image all 4 channels are active. It has to be printed in 2 colors, what is the smart way to whiten the Y-C channels without altering the image appearance? Thank you

 

[thebestcpu]

Hi @erlebe

Firset, I wanted to point out that this website does not present the colors of a CMYK image properly, The following image in RGB would display the colors much more closely:



That said, the approach I would take to eliminate the C and Y channels is by adding a channel mixer adjustment channel.
Set the C output channel with the C slider to (other channels are already at 0)
Set the Y output channel with the Y slider to 0 (other channels are already at 0)
Leave the M output channel alone
For the K output channel, slide the C and Y sliders primarily and mostly in equal proportions to compensate for the absence of the C and Y channels. You can fine tune all the channels until your are satisfied that it is close enough (using color sampling tool would help tune it in more accurately)

When you are done, you just look at the Channels Pallet and you will see that the C and Y channels are turned off (all white) and you only are using the M and K channels

Hope this helps
John Wheeler

 

[erlebe]

Thank you. I have tried this already but at the end a 9% Magenta remains over the Black. It's the M that with the Y&C is over the B in the first image. I cannot lower the M in the B channel without effecting the M value

 

[thebestcpu]

Hi @erlebe
Good catch. I am assuming then that it is OK to have Magenta and Black in the areas of the Magenta rectangle and the overlaid magenta ciircle.

If the case all you need to do is the same procedure with two channel mixer adjustment Layers.
For the frist Channel Adjustment djustment Layer mask it to cover the rectangle and the circle area of Magenta and proceed as I inidcated before.
In the second Channel Adjustment Layer you use the inverse mask and turn down the CMY all to zero and then adjust the K level by bringing up the CMY sliders to get the original luminosity yet now on with K.

HOpe that does it unless my assumptions are incorrect about having Magenta not anywhere on the gray lines (the original image does incude magenta on the gray lines under the magenta circle so was following your need to not change the color of the image. Yet if that is incorrect, that too can be solved with just chaning the mask and still use two Channel Adjustment Layers

Let me know if that does it for you
John Wheeler