6 Replies Latest reply on Jul 19, 2009 9:55 AM by jimzepellin

    CMYK RGB confusion


      Recently I have had to get myself involve in work for print and coming from a digital background I have a very a very tenuous grip on the working of getting material ready for print.

      Recently while scanning a forum on a totally unrelated subject I spotted these two quotes from two different people.


      'unless you have experience preparing images for commercial print and your client has specified CMYK for offset printing DO NOT supply CMYK images - stick to RGB output.'


      'yes i wouldnt use CMYK  images.
      because most/all printers have there own convertion algorithms so the printer will convert a CMYK image back to RGB then convert it back to CMYK.
      so you will lose a bit of quality'


      This confused me as I have always been told to supply CMYK. I have a very vague recollection that this has been mentioned to me before by a client but this is so vague it might as well have been a dream and was before I started getting involved with print. I just wondered if anyone could clear this up for me.


      Thanks for any help.

        • 1. Re: CMYK RGB confusion
          Lou Dina Level 3



          It's a bit of a free for all out there.  The best course of action is to have a discussion with the printer you plan to use and get on the same page.  They may insist on RGB or a certain flavor of CMYK.  In general, though, I find that if I supply CMYK files, most printers usually just sends those files straight through, without doing any conversion.  If they convert them and the color gets whacked, it may come back to haunt them. Some printers know how to handle and convert RGB files properly, and others do not.  I've done a fair amount of this, and personally, I would always prefer to supply CMYK files so I control the conversion, but I'd have a discussion with the printer first or look for clear, precise specs (and preferably their custom CMYK profile) on their website (which many don't provide).


          That's where the contract proof generated by the printer can come in handy.  If you insist on a contract proof, then sign off on the color, placement, layout, etc, the printer has to hit that target on press within reasonable tolerances, otherwise you are eligible for a free reprint.  Those tolerances can be fairly liberal, but decent printers usually come very close to matching their own proof.


          As Rick McCleary mentioned on another thread on this forum.....we are neither 'here' nor 'there', but somewhere in between in the evolution of digital printing.  That won't change fast, I'm afraid.  Too much legacy equipment, approaches, etc.



          • 2. Re: CMYK RGB confusion
            John Danek Level 4

            I concur with Lou on this one, but I think vendors have a tendency to accept CMYK over RGB files because of the fact that some customers like what they see on their monitors and then expect that to come off the press.  Virtually two different color spaces and two different methods of delivering that color ( RGB = transmissive, CMYK = reflective ).  Where this becomes a bit more complicated is when the files are RIP'd + PRINTED.  The color gamut on even an offset press cannot match what is seen on the monitor and/or printed on an inkjet ( in some cases ).  Print vendors prefer CMYK because it makes the job predictable.  And, because of the many variables in RGB and CMYK color settings, CMYK narrows those variable to a manageable point.


            Now, I believe ( as does Lou ) the print vendor is the one you should listen to.  There are photographic environments where RGB is preferred for the mere fact that the photographs will print inkjet and the inkjet will retain more color gamut than other print processes.  But, if you are preparing files that are equipped with accurate color ( for instance, a Pantone match ) and are destined to be printed in offset, then CMYK files are preferred and, you should be able to get them proofed before committing to the final press run.  The two quotes you mentioned in your post are irresponsible and inaccurate.  There's a reason why vendors require CMYK, even now.  All of the print vendors I use require CMYK and I haven't run into one yet where they'll accept RGB files.

            1 person found this helpful
            • 3. Re: CMYK RGB confusion
              p_d_f Level 2

              The original poster has been confused by the word "printer".


              In one context it mean the Epson, Canon or HP inkjet printer, and those do in fact want RGB if you don't have a RIP. In the other context, the word "printer" refers to a commercial offset lithographer, who will invariably insist on some form of CMYK file to print, as they typically know not what RGB is or does. The only confusion here is in what printer is being referred to.

              1 person found this helpful
              • 4. Re: CMYK RGB confusion
                Printer_Rick Level 4

                The printer will probably prefer CMYK. But if possible - get one or more CMYK press profiles from the printer, based on the stocks they use. If they don't give you one, ask which ones they use


                CMYK profiles contain total ink limit information. This is very important relating to the paper. Uncoated paper cannot accept as much ink as coated paper.

                • 5. Re: CMYK RGB confusion
                  Ramón G Castañeda Level 4

                  "Printer" in English also has the ambiguity of applying indistinctly to the printing machine itself and to the print shop or the individual(s) who run it.  Other languages avoid that, e.g. German Drucker vs. Druckerei, Spanish impresora vs. imprenta, etc.

                  • 6. Re: CMYK RGB confusion
                    jimzepellin Level 1

                    Thanks for the info guys.All good advice is very welcome.