Hi Pawel

All I can say is this. I have worked my entire professional life as an advertising art director and graphic designer. I have created literally hundreds of full color magazine advertisements and hundreds of full color brochures. In my new life I create 3D stereograms for publication.

I provide either a PDF/X3 document or a CMYK TIFF (I have to admit that I convert my RGB TIFF to CMYK in Photoshop). I have never been asked by a printer for a rasterized image. And to be honest, if a printer asked me to rasterize my images, I would find a more professional printer!

What you are referring to is a halftone color separation. Where the image is converted from "continuous tone" to tiny dots. Four plates, C, M, Y, & K are created.

I have used programs that can do this, and the results are just OK at best. If the screen angles are not perfect, you can get a moire, and a digital halftone dot is not as fine or precise as a film generated halftone dot.

And, this is not my job. This is the printer's job and the printer has had a heck of a lot more experience and knows the expectations and limitations of his equipment. He is the only person I will trust to "color separate" my images.

For more information see https://en.wikipedia.org/wiki/CMYK_color_model