4-color black and white images, GCR and Custom CMYK

[tetragon_a]

Hi, I've been asked by a printer / client to adapt a 4-color black and white image using heavy GCR to prevent any color cast and ensure the K channel is dominant. I've been advised to do this by using Convert to Profile / Custom CMYK and adjusting the GCR black generation to Heavy. I've also read elsewhere that Custom CMYK is some sort of 90s aberration and it's better to pull out your eyes than use it. What's the best way of getting good results here? They're only asking me to do this for the black and white images in 4 colours. It's using FOGRA52 uncoated (side-note: converting to a custom profile doesn't include this as an option…).

[Kevin Stohlmeyer]

@NB, colourmanagement this sounds right up your alley!

[NB, colourmanagement]

I agree with the folk who say "custom CMYK" is an aberration. I'd recommend perhaps editing the relevant FOGRA profile's black curve using a profile editor. 

Neil Barstow Colourmanagement. 

google me for lots of free info. 
hope this helps. 

[Stephen Marsh]

@tetragon_a 

I'll post some practical advice a bit later on how to prepare for F52.

[Stephen Marsh · Accepted solution]

@tetragon_a 

I have uploaded the test .PSD file, the .ATN action file and the 3 .ICC profiles are required for the action to run without errors. You will need to install the ICC profiles before running the action.

Download link:

https://www.dropbox.com/scl/fi/n7w2h65j3ygrgou44t4jh/Fogra-52-Neutral-Heavy-GCR-Conversion.zip?rlkey...

You can compare a standard conversion vs. the action, CMY vs K channel, Lab values etc. Use at your own risk and all standard disclaimers, however, I believe or at least hope that you will find it useful :]

[tetragon_a]

Thank you so much! Did you make / alter these yourself? I'm not totally sure I know where to start here, or how to check the accuracy of what I'm liable to get out - any pointers / links to other threads where this has been dealt with?

[Stephen Marsh]

These are all standard profiles.

The action is a hack, a kludge, making do with Photoshop tricks in lieu of using ICC profile generation software.

Where to start? Install the ICC profiles. Load the action. Run the action, a flattened image Background layer is required. Compare the results vs. a standard conversion to Fogra 52.

Compare the CMY vs K channel visually and with CMYK info readings. Look at the neutral values with the info panel set to Lab readout. Check the total ink limit/total area coverage etc.

Pass a few sample conversions back to your print service provider and ask for their comment.

A similar topic for a different print target:

https://community.adobe.com/t5/photoshop-ecosystem-discussions/my-b-amp-w-cmyk-print-files-with-the-...

[tetragon_a]

I've just done this and created 2 files from your psd (one run with your action/profiles) and one with a 'straight' conversion via 'convert to profile'. I see that the one using your steps is more neutral and has a more subtle range of tones. Is that what I should be seeing?

I have another file that needs to be converted from greyscale to CMYK 4C. Is this advisable and how would you do it? With the same workflow?