34 Replies Latest reply on Feb 8, 2018 9:01 AM by Lumigraphics

    Conversion from RGB to CMYK press ready of a problematic image

    GaudiumMagnum Level 1

      I'm trying to convert an image from RGB to CMYK for press.
      The conversion has some troubles as image use a lot of colours out of gamut, and also i need to convert to a 300% total ink CMYK profile (such as ISO coated v2 300).

      I'm not satisfied with Photoshop conversion from Adobe RGB to Iso coated v2 300 (this is the common profile used by some media partners)... do you have any hints or suggestion?
      I know that is quite impossibile to obtain the same vivid and brilliant colours.

       

      I attach the "problematic" piece of image.

       

      sample.jpg

        • 1. Re: Conversion from RGB to CMYK press ready of a problematic image
          Mylenium Most Valuable Participant

          You will probably have to split up the channels and re-compose them after tweaking them individually. And yeah, spot colors would definitely help.

           

          Mylenium

          1 person found this helpful
          • 2. Re: Conversion from RGB to CMYK press ready of a problematic image
            GaudiumMagnum Level 1

            Thanks

            Unfortunately... i don't think spot colours should be available, as we are talking about standard offset print with simple process colours (at least 4-5 different media, so i have to think to the worst scenario)

            Which kind of manipulation do you take into consideration for single channel tweaking?

            • 3. Re: Conversion from RGB to CMYK press ready of a problematic image
              D Fosse Adobe Community Professional & MVP

              There isn't a whole lot that you can do. Remember, you can't exceed 300% total ink!

               

              Keep your info panel up, with a readout for total ink. Then try to push ink coverage as far as you can without going over.

              • 4. Re: Conversion from RGB to CMYK press ready of a problematic image
                JonathanArias Adobe Community Professional

                are you doing a layout in indesign? why not just place your RBG image in the layout, and let indesign handle the color conversion when it created a .pdf for printing?

                • 5. Re: Conversion from RGB to CMYK press ready of a problematic image
                  GaudiumMagnum Level 1

                  mmm... yes i'm working with InDesign.
                  I need to output a PDF/X-1a with ISO Coated v2 300... do you think InDesign works better on colour conversion than Photoshop directly? ... or Distiller from .ps file with an RGB image linked...
                  I have never tried...

                  • 6. Re: Conversion from RGB to CMYK press ready of a problematic image
                    c.pfaffenbichler Level 9

                    Watch out for banding.

                    Do you have the layered RGB File in 16 bit?

                    • 7. Re: Conversion from RGB to CMYK press ready of a problematic image
                      norman.sanders Adobe Community Professional & MVP

                      Since you are constrained by a total ink % limit and not being able to use touch plates or (I assume) varnish, there is one other element that can have a significant effect on contrast, density range and color brilliance of the process colors: the paper stock. If a choice is available to you, inquire about very high gloss and cast coated paper availability. They will certainly help.

                      • 8. Re: Conversion from RGB to CMYK press ready of a problematic image
                        GaudiumMagnum Level 1

                        No ... unfortunately ... we are talking about ADV on magazines, this is the reason for 300% total ink limit. I cannot expect great quality in printing and paper.

                        • 9. Re: Conversion from RGB to CMYK press ready of a problematic image
                          JonathanArias Adobe Community Professional

                          i let indesign doing all of my color conversion. i place RBG mode images from photoshop. or rbg mode vector art. select .pdf for print and have indesign handle the color conversion.

                           

                          you can, in the output section, select "to desitination" and select what you want. but i rarely do that even. i just select .pdf for print and let indesign do its thing. 

                          • 10. Re: Conversion from RGB to CMYK press ready of a problematic image
                            c.pfaffenbichler Level 9
                            i place RBG mode images from photoshop. or rbg mode vector art

                            That would seem risky if the vector art includes black elements.

                             

                            you can, in the output section, select "to desitination" and select what you want. but i rarely do that even. i just select .pdf for print and let indesign do its thing.

                            That sounds unclear …

                            The indd files itself should always have the proper profiles assigned and when separating on pdf-export the pdf Output Destination should be set to »Document CMYK - …«.

                            • 11. Re: Conversion from RGB to CMYK press ready of a problematic image
                              GaudiumMagnum Level 1

                              mmm but you don't know exactly before that how the colours will be ... i prefer to work on CMYK directly on Photoshop to correct some issues and troubles related to conversion... but in this case is really difficult to get an acceptable conversion.
                              Anyway i will try.

                              • 12. Re: Conversion from RGB to CMYK press ready of a problematic image
                                D Fosse Adobe Community Professional & MVP

                                First make sure the RGB file is max neutral black 0-0-0. That converts into ISO Coated 78-68-58-94 - that's the blackest black you will ever get in ISO Coated (ECI) 300%. That is 300% coverage, that's a brick wall you can bang your head on.

                                 

                                The spectral colors, from Adobe RGB, will be partly out of gamut in ISO Coated - mostly the yellow-greens and the deep blues. You really need to soft proof this and make the appropriate adjustments. The greens will show blocking-up and banding, and the deep blues will very likely turn purple.

                                 

                                Don't worry so much about total saturation. This won't be seen side by side with the RGB version. Just get it to look good with smooth, even gradients. That's much more important.

                                2 people found this helpful
                                • 13. Re: Conversion from RGB to CMYK press ready of a problematic image
                                  JonathanArias Adobe Community Professional

                                  that is why you print a proof. you should to that anyways if you are working in print.  Just sharing how i do it. i do 600k worth of printing a year. and i don't go back and forth converting from photoshop. i let indesign do my color management.

                                  2 people found this helpful
                                  • 14. Re: Conversion from RGB to CMYK press ready of a problematic image
                                    Lumigraphics Adobe Community Professional

                                    Honestly, I would do two things:

                                     

                                    1. Talk to the printer about how they want the file prepared. They may want the ID file and do the separations themselves.

                                    2. Go back to the client and tell them that four-color on cheap paper is going to look awful.

                                     

                                    This is going to be out of gamut unless you do six-color and decent coated paper.

                                     

                                    As for proofing, do several variations tiled in one pdf and see what looks best.

                                    • 15. Re: Conversion from RGB to CMYK press ready of a problematic image
                                      GaudiumMagnum Level 1

                                      File has to be sent to main stream media print services which have strict tech speciments (PDF/X-1a, iso coated v2 300 CMYK profile, only process colours CMYK).

                                      I have no choice about paper (maybe grade 5 o 3 coated paper, but i'm not sure), no additional inks, etc...

                                       

                                      I will try with some tweaking as suggested... but you are wright... this is going to look quite awful...

                                      • 16. Re: Conversion from RGB to CMYK press ready of a problematic image
                                        D Fosse Adobe Community Professional & MVP

                                        GaudiumMagnum  wrote

                                         

                                        this is going to look quite awful...

                                         

                                        That's the wrong attitude. It will not look awful if you do it right. It will look consistent with the nature of the medium. As I said, this will not be compared with anything else. It will stand on its own.

                                         

                                        I live in this world. I just finished preparing 250 files for a book, in ISO Coated 300%. Each file is custom prepared for the paper that will be used - bringing out what can be brought out, and compensated for what can't. I had my monitor white point set to that paper color, and the black point set to max ink density for that paper. Then I proofed. I know what'll come out of the press.

                                         

                                        People get all hung up on total saturation. It's not important. Good color is about color relationships, not total saturation. Get a color to work with the others, and it'll look good.

                                        3 people found this helpful
                                        • 17. Re: Conversion from RGB to CMYK press ready of a problematic image
                                          c.pfaffenbichler Level 9

                                          Good color is about color relationships

                                          Indeed, otherwise newspapers printed on uncoated greyish stock would not even need to bother with color images.

                                          • 18. Re: Conversion from RGB to CMYK press ready of a problematic image
                                            chanaart Adobe Community Professional

                                            Best to place the image in Indesign. InDesign converts RGB to CMYK better than Photoshop.

                                             

                                            Chana

                                            1 person found this helpful
                                            • 19. Re: Conversion from RGB to CMYK press ready of a problematic image
                                              c.pfaffenbichler Level 9
                                              InDesign converts RGB to CMYK better than Photoshop.

                                              How do you figure that?

                                              • 20. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                GaudiumMagnum Level 1

                                                You are wright, but this is the right path when you have control over the job.
                                                Consider that this image has to be used in 4-5 different services, with no control (and specs) over paper and no proof, so i have to get a compromise acceptable for ... uhm... some generic coated paper.

                                                Maybe "awful" is not the right term (sorry ... my english is poor), but i meant that i know that i will not get a "spectral color" so "beautiful" as the RGB file. This is the only case which give me troubles in conversion... in different scenario i found relative easy to get a nice conversion from RGB to CMYK, working on colours...

                                                So i undertand that there is no easy way to avoid "blocking-up and banding" (i'm not worried about colours), and that it's necessary correct point-to-point image to get a smooth transition between colours (and also working on colours itself).

                                                • 21. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                  c.pfaffenbichler Level 9
                                                  Consider that this image has to be used in 4-5 different services, with no control (and specs) over paper and no proof, so i have to get a compromise acceptable for ... uhm... some generic coated paper.

                                                  While some publications indeed do not provide their print specs online the websites for many do feature them, pretty well hidden at times, though, unfortunately. And As a last resort one can usually call up someone at the publisher’s – though if one gets the reply »CMYK« when asking for the print space it’s usually to no avail …

                                                  This is where separating placed RGB images at pdf export from Indesign really offers convenience – when one has to provide pdfs for many different print conditions.

                                                   

                                                  In any case using the same separation for newspaper print and magazine print would not be OK.

                                                  • 22. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                    GaudiumMagnum Level 1

                                                    Fortunately the media is magazine only (no newspaper... for this media they have a different ADV).

                                                    • 23. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                      GaudiumMagnum Level 1

                                                      c.pfaffenbichler  ha scritto

                                                       

                                                      This is where separating placed RGB images at pdf export from Indesign really offers convenience – when one has to provide pdfs for many different print conditions.

                                                      What do you mean exactly?
                                                      Which kind of predefinite (or customized) job do you use to export (or distill) PDF with RGB images? Do you leave no CMYK profile assigned for output?

                                                      Consider that some media portal require CMYK images to accept the file, and avoid any automated conversion (or charge it) from RGB to CMYK.

                                                      • 24. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                        c.pfaffenbichler Level 9

                                                        I hardly ever embed RGB images in pdfs, for example to avoid missing banding that might become apparent at separation.

                                                        When one places profiled RGB images one can convert them to the indd file’s Color Space when exporting the pdf (Destination: Document CMYK - …).

                                                        indesignPdfDestinationDocumentCmyk.png

                                                        BY the way: If necessary one can change the Rendering Intent (Object > Image Colour Settings) for individual images in Indesign.

                                                        1 person found this helpful
                                                        • 25. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                          GaudiumMagnum Level 1

                                                          Ok, it's clear now what you mean... but have you experienced difference on final printed work between this method vs adding CMYK images directly?
                                                          Consider that i'm sure at least that these services use-and-require ONLY ISO Coated v2 300 (maybe another similar one... but i have to check...)

                                                          • 26. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                            c.pfaffenbichler Level 9

                                                            I can attest to no difference between Indesign’s separation and Photoshop’s provided the settings on both applications are according.

                                                            When placing CMYK images in indd just make sure not to repeparate at export – but this should not be an issue if indd and the placed images share the same Colour Space.

                                                            • 28. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                              D Fosse Adobe Community Professional & MVP

                                                              In this case I suspect I would end up creating the spectrum in ISO Coated, taking care to maintain smooth, even gradients in each color channel. Remapping this from Adobe RGB is difficult. Possible, but difficult.

                                                               

                                                              You have to keep in mind that this particular image is a demonstration piece for gamut clipping. Even if I tried, I couldn't think of an image where the effects would be more conspicuous. Here - this is what gamut clipping looks like, worst case scenario. Normally, letting the profile do it is good enough, with minor adjustments. This takes a little more.

                                                               

                                                              Print profiles let you choose rendering intent (working RGB spaces don't support that). That should take you some of the way - in this case I think Perceptual looks a lot better than Relative Colorimetric. But it still takes some work.

                                                               

                                                              Keep soft proof on while you work, to monitor the result of the adjustments. Gamut clipping, by definition, is the point where any color channel hits 0 or 255/100. So look at individual channels. Convert a copy of the file just to note the areas where this happens. Look at the histogram and the individual channels. Generally, use whatever preferred tool in combination with "Blend If" to target the high or low ends of each channel specifically.

                                                              2 people found this helpful
                                                              • 29. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                                GaudiumMagnum Level 1

                                                                Thanks for your help.

                                                                Yes... unfortunately there are no magical photoshop functions unknown to me (or to us) to do that ... (maybe in future with the AI help integrated in color separation ?!?) there is some work here to do... you give me some useful hints, thanks again.

                                                                • 30. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                                  NB, colourmanagement Adobe Community Professional

                                                                  Hi

                                                                   

                                                                  I am coming to this late, but I'll mention that, if you decide to (it was advised above) - edit images in CMYK that needs care -

                                                                  WHY? - well, the fact the image is already "in" CMYK  does not constrain the gamut, so have a care if you decide to push the colour or levels after conversion to CMYK. Because doing that you can violate the ink limit.

                                                                  This would lead to a VERY unhappy pressman.

                                                                  That's why many press experts like Don Hutcheson prefer to work in RGB with soft-proofing active - then convert. That RGB to CMYK conversion restricts the colour to what CAN be printed by keeping the total ink values within the limits of the ink and paper (as expressed by the ICC profile).

                                                                   

                                                                   

                                                                  This next tip applies to future projects, not your current conversion, but you may find it of some use.

                                                                   

                                                                  Occasionally smoothness in very high gamut (i.e. a long way out of destination gamut) images can be improved by using a device link profile. Thosem profiles can be set up to more properly take gamut mapping into account than the standard ICC process.

                                                                  BUT, at last look, Photoshop unfortunately did not support RGB to CMYK device links.

                                                                   

                                                                  Photoshop can use device links in conversions, but only CMYK to CMYK, it seems.

                                                                  Many feel that device link profiles are all about keeping clean blacks in CMYK to CMYK conversions but there's much more to device links than that.

                                                                   

                                                                  So, the area where device link profiles really excel is in CMYK to CMYK, and as Photoshop can use them now it can be worth a try.

                                                                   

                                                                  If you were printing on a low gamut medium, say uncoated [a pretty unsaturated medium], you may see improved results by first using the standard Photoshop convert to profile process - converting from RGB to a large CMYK colourspace (like ISO coated v2) then using a device link between ISO coated V2 and the uncoated icc profile.

                                                                  I've seen this improve vital detail in saturated areas. Of course, though, it cannot put more ink on the paper than the paper can take.

                                                                   

                                                                  Then theres channel blending as championed by a man who sued to be known by some as "the arch anti calibrationist" Dan Margulis. That truly can work wonders in bringing out detail in poor separations

                                                                   

                                                                  It's nice to be able to do device link conversions in Photoshop now, of course you also need someone to make the device link profiles for you.

                                                                   

                                                                   

                                                                  I hope this helps

                                                                  if so, please do mark my reply as "helpful"

                                                                  thanks

                                                                  neil barstow, colourmanagement

                                                                  • 31. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                                    D Fosse Adobe Community Professional & MVP

                                                                    Yes, I would normally advise RGB master > convert to CMYK, partly to avoid exceeding max ink (and partly to repurpose for different processes).

                                                                     

                                                                    However, the spectral colors here is a special case, because of the smooth transition required between them. Remapping this from Adobe RGB into ISO Coated without banding is very tricky. I didn't fully realize just how tricky until I tried. It can be done, but it takes a good deal of time and effort. It might save some labor to do it in ISO Coated to begin with, picking colors that are already within gamut.

                                                                     

                                                                    Yes, Channel Mixer can be very effective to control gamut clipping - but in that case it should be used in combination with "Blend If", to target the range where the clipping actually occurs. If the clipping is at the low end of any given channel, there's no reason to desaturate the high end unnecessarily.

                                                                    • 32. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                                      GaudiumMagnum Level 1

                                                                      https://forums.adobe.com/people/D+Fosse  ha scritto

                                                                       

                                                                      Yes, I would normally advise RGB master > convert to CMYK, partly to avoid exceeding max ink (and partly to repurpose for different processes).

                                                                       

                                                                      However, the spectral colors here is a special case, because of the smooth transition required between them. Remapping this from Adobe RGB into ISO Coated without banding is very tricky. I didn't fully realize just how tricky until I tried.

                                                                      Yes i can confirm that this is not an easy job, and require time... but... in this SPECIAL case i think that there are no other way to do that and get a smooth transition... i have tried a lot of combination in conversion, but nothing give me an easy solution...

                                                                      • 33. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                                        NB, colourmanagement Adobe Community Professional

                                                                        DFosse,

                                                                         

                                                                        Oh for that spectrum image I agree. It's really likely it will be a lot easier to create that specific effect in CMYK.

                                                                        But its really important to watch those ink limits.

                                                                         

                                                                        My note of caution about violating ink limits was more directed to those who read this thread later and perhaps might push the saturation images post conversion.

                                                                         

                                                                        I'd convert first, observe the locations of the highest ink values, then make it in CMYK and place eyedroppers in those same areas.

                                                                        Watch the values, its very easy to go over 300 in dark areas.

                                                                         

                                                                        I hope this helps

                                                                        if so, please do mark my reply as "helpful"

                                                                        thanks

                                                                        neil barstow, colourmanagement

                                                                        • 34. Re: Conversion from RGB to CMYK press ready of a problematic image
                                                                          Lumigraphics Adobe Community Professional

                                                                          Technical details aside, you need to set expectations with your client. As long as the client is satisfied with the finished results, you are golden. Do your best, bill accordingly, and let them know that simpler artwork will give better results next time.