CMYK PDF colours have brownish tinge

Hi,

We need to know more about how you are converting to CMYK. 

Also, I hope you archived a copy of your original RGB files.

A CMYK colour space is "printing device" specific and sometimes rather a small colour space so saturation is often lost when converting, there's no going back from CMYK to RGB, really. 

Maybe that tint you see is a 'proof' of the paper "white' colour defined in the CMYK ICC profile.  Not all paper IS white.

Some ICC profiles define a warm tone paper colour, could be that’s what you are seeing.

You'd see the tint in the CMYK profile if you open an RGB image, now set Photoshop to view/ softproof / custom, choose the CMYK profile** the printer either gave you or told you to use -  'paper white' should be checked to reveal the paper colour. 

**If the printer just told you "CMYK", that’s no good, it's like telling the postman a street without a house number, guessing isn't going to be a good idea.

Press types and paper types produce different CMYK ICC Profiles.

more here: https://www.colourmanagement.net/advice/about-icc-colour-profiles/

and here: https://www.colourmanagement.net/advice/prepress/

BTW, self print also involves CMYK (even if the process accepts RGB images), basically that’s because its print, RGB is an additive process - R+G+B light = white, CMYK is subtractive, C+M+Y+K = black.

One can't print full colour with R. G and B inks even if you could get them. 

I hope this helps

if so, please "like" my reply and if you're OK now, please mark it as "correct", so that others who have similar issues can see the solution

thanks

neil barstow, colourmanagement.net :: adobe forum volunteer

[please do not use the reply button on a message in the thread, only use the one at the top of the page, to maintain chronological order]

"the printers require CMYK..."

Yes, but which CMYK? You have to ask the printer. If you're not getting an answer, ask someone else. You need to know which CMYK profile to use.

There is no such thing as a generic "CMYK". There is only a series of specific CMYK profiles, each one representing a particular process. A CMYK profile is a representation of a specific press/paper/ink combination, and to get a good result, your file needs to be prepared accordingly. Use the wrong profile, and the result may not only look bad, but at worst be unprintable.

The Photoshop default just happens to be US Web Coated (SWOP) v2, because there has to be some default, and a fair number of presses in the US conform to this standard when printing on coated paper. But not all. And nowhere outside the Americas.

This may be more than you bargained for, but CMYK is really not for beginners. It's a can of worms, and you need to know what you're doing.

Then change printer!

If you're preparing artwork for a color book, the professional approach (in brief) would be to optimise your RGB images in Photoshop, then Place them in InDesign where you can add the text and then export the pages to a PDF/X-4 (or the PDF your printer wants).

You can check the effect of your artwork being printed in CMYK by soft proofing.

Keep to RGB color mode, if you've already  coverted to CMYK, go back to the originals again, always work in RGB.

The color of pages that should be white? Sounds like the effect of converting using an Absolute Colorimetric intent; you don't want to be doing so.