Affinity Designer (Windows) - Best way to export from CYMK to RGB with #000000 absolute black?

[gidkid]

I was working on exporting from CMYK to RGB to render box art in 3D. For this project I needed to create masks for the special print regions (foil, UV coating etc.) from existing box art vector files. I created black and white masks with the black set to #000000 or RGB zeroed out, but when I exported it was #080605 and throwing my masks off a bit. I tried changing the color profiles in the exporter but that didn't seem to help.

I can change the document from CMYK to RGB, and export to get pure blacks, but I'm wondering if there is another way to do this without changing the document back and forth from CMYK.

[NotMyFault]

Can you provide a test document, and screenshot of the export settings?
 

It can depend on color profile and export settings.

Normally cmyk 0, 0, 0, 100% should give pure black as RGB export, or try 100% on all channels.

[Print Monkey]

Try defining a "rich black" spot color.

1. go to swatches panel.
2. click the = hamburger and do "add global color" and name it "Rich Black"
3. select CMYK for the sliders
4. set CYM and K to 100% (this is called "rich black" and isn't normally used at 400% ink coverage because it makes a mess that way when actually printing. See here https://www.prepressure.com/design/basics/rich-black if you actually need to print rich black. Something more like 40,40,40,100 is more common but different printers and processes need different formulas)
5. Assign that spot color to whatever needs to be RGB #000000

I just tested and it seems to work, at least as the normally unusable 100,100,100,100. Not sure exactly what CY and M minimum % is needed to get RGB #000000 with which profile you're using but it's helpful to have this kind of thing as a spot color anyway because it makes it easier for the printer to just edit the CMYK assignments even if it isn't printed as a spot color.

(Edit: actually 100% of everything is called Registration Black because it's used to print registration marks. Rich black is always something less than 100% C M and Y.)

[gidkid]

Thanks for the suggestions, I'll give setting it to a rich black a try! 👍

I'm familiar with the basic CMYK work flow for blacks since I've worked with designs/illustrations going to print so this makes sense.

I can always just convert the document to RGB and work that way too if I know the design is final. 👍

[Print Monkey]

Probably the best thing to do if you need to output to both RGB and CMYK is just use AdobeRGB as the working profile, export to sRGB for RGB images, and either use soft proofing combined with exporting directly to the CMYK profile or like you say convert to the target CMYK profile to make manual adjustments to CMYK values for the output printer. CMYK is "fundamentally reflective" and RGB is "fundamentally emissive", and it's hard to reflect 0 but theoretically easy to emit zero, and the CMYK profiles are based on reflective measurements from the paper. I think the ICC CMYK profiles also effectively have ink limits for perceptual rendering which results in RGB 0 not being zero. This color management stuff is such a pain I don't know how anyone ever figures it out.