14 Replies Latest reply on Nov 12, 2008 9:53 AM by (christine_sirois)

    Out of Gamut or convert to profile?

      HI

      in this link: http://www.adobe.com/digitalimag/pdfs/phscs2ip_reproprep.pdf
      in page number 6, hi say: "steps you can take to alter the colors to bring them into gamut..."

      May question it's: why we need this technique if we convert this file from RGB to CMYK profile and then anyway all the color it's in gamut cmyk?

      thank
        • 1. Re: Out of Gamut or convert to profile?
          John Danek Level 4
          The danger is, even though you are converting from RGB to CMYK "on the fly", certain RGB's are inherently out-of-press gamut ( i.e., sRGB ), so there's a risk of gamut clipping where an image can land flat or banded. If you convert without taking gamut into consideration, you could end up with bizarre color rendering. There is alot of pressure to "automate" the color rendering process and the results can be seen in everything from magazine ads to outdoor billboards. For the past couple of years, there's been an increased tolerance for bad images.

          The example shown in the PDF is one technique among a few where the image can be optimized and/or corrected to conform within industry limitations. I'm not done reading the piece, but it looks compelling. Thank you for supplying the document, I'm going to study it.
          • 2. Re: Out of Gamut or convert to profile?
            (Marco_Ugolini) Level 1
            If the out-of-gamut colors are sufficiently off, clipping may occur, specially when using the Relative Colorimetric rendering intent. Clipping in highly-saturated areas of an image produces a loss of visible detail, which in most cases is an undesirable result.

            Even when using the Perceptual intent, one can target the out-of-gamut colors that are more at risk of clipping by using a combination of soft-proofing and a variety of adjustment tools (Hue/Saturation first among them) to produce a more-pleasing result.
            • 3. Re: Out of Gamut or convert to profile?
              Gernot Hoffmann Level 3
              "For the past couple of years, there's been an increased
              tolerance for bad images."

              Indeed, for instance JPEG instead of ZIP for ordinary
              menue screenshots in the mentioned PDF.
              Examples for other bad images are the gamut visualizations.

              Best regards --Gernot Hoffmann
              • 4. Re: Out of Gamut or convert to profile?
                Level 1
                Hi frendis

                I still dont understand one point:

                let say my printer (process) tell me close file cmyk with some profill for his paper... so i take my original RGB image and then convert him to his profill cmyk.

                it's not a right way? or should we use technique like in page number 6?

                thank
                • 5. Re: Out of Gamut or convert to profile?
                  Gernot Hoffmann Level 3
                  You should convert your RGB images so to CMYK,
                  that the CMYK images are looking pretty good.
                  That's not done by a formal RGB-CMYK conversion,
                  because it can happen that many RGB colors are
                  mapped to the same CMYK color.
                  For instance here, the orange grass, page 10:
                  http://www.fho-emden.de/~hoffmann/labproof15092008.pdf

                  More about in Dan Margulis' books.

                  Best regards --Gernot Hoffmann
                  • 6. Re: Out of Gamut or convert to profile?
                    Level 1
                    HI Gernot Hoffmann

                    thank for youer pdf.

                    can you tell me when i should use technique like in page 6?

                    thank
                    • 7. Re: Out of Gamut or convert to profile?
                      Gernot Hoffmann Level 3
                      Koki,

                      the author starts on p.6 to explain, how
                      the colors can be altered. P.6 itself shows
                      only the gamut warning: out-of-gamut colors
                      are indicated by gray.

                      If we use Proof Colors instead of Gamut
                      Warning then we'll see HOW different the
                      monitor view and the print will be. Some-
                      times the change is not dramatical, some-
                      times the colors HAVE to be manipulated.
                      Judging about the prospective printing quality
                      requires some experience, therefore I don't
                      have a simple answer to your question 'when..'.

                      Best regards --Gernot Hoffmann
                      • 8. Re: Out of Gamut or convert to profile?
                        Level 1
                        thank!!!!!
                        • 9. Re: Out of Gamut or convert to profile?
                          Tim Lookingbill Level 1
                          Koki,

                          Take some correctly exposed pictures of very vibrant flowers of yellow, blue, red and orange hues lit by the sun opprox. 30 degrees off horizon.

                          Try to retain the density detail within the petals of the flowers as you Soft Proof to your printer of choice. When you see these flowers go posterized or lose density detail Soft Proofing that's one of the instances when you apply that technique.
                          • 10. Re: Out of Gamut or convert to profile?
                            Gernot Hoffmann Level 3
                            Tim,

                            that's IMO a rather difficult experiment:

                            a) correctly exposed,
                            b) just now in autumn (northern hemisphere), when
                            we don't have many vibrant flowers flowering,
                            c) lit by the sun approx. 30 degrees off horizon,
                            but without clouds.

                            Ähem - just this effect was demonstrated by Orange
                            Grass (instead of flowers) here:

                            http://www.fho-emden.de/~hoffmann/labproof15092008.pdf

                            Best regards --Gernot Hoffmann
                            • 11. Re: Out of Gamut or convert to profile?
                              Tim Lookingbill Level 1
                              Gernot,

                              I was just giving him some parameters as to when he'ld have to implement such an edit. It's not meant as a test or an experiment.

                              I've had some images I thought would gamut clip horribly Soft Proofing PS's standard SWOP profiles but show no such shift in color detail. And some of the RGB data in some of the colors went close to 255 but it was a very bright midday sunlit image. It seems high contrast and somewhat darkly rich and colorful images suffer from this gamut clipping proofing to CMYK.
                              • 12. Re: Out of Gamut or convert to profile?
                                Level 1
                                thank for all, friends!

                                Gernot, do you now whay illustrator don't support LAB!?

                                thank
                                • 13. Re: Out of Gamut or convert to profile?
                                  Gernot Hoffmann Level 3
                                  Koki,

                                  yes, images in Lab cannot be placed or imported
                                  - it's simply missing.
                                  But as you know - Lab for Pantone spot inks is
                                  available.

                                  Best regards --Gernot Hoffmann
                                  • 14. Re: Out of Gamut or convert to profile?
                                    I have an Ills. CS3 file with imported greyscale images with their opacity lowered directly in Illustrator. When I flatten and save the file I get an "out of gamut" warning. I can't see the gamut warning in photoshop because the images are greyscale and the option is greyed out. Even if I convert to cmyk, I don't see any clipping. Does anyone know if Illustrator itself has gamut correction tools.

                                    I am trying to get a color proof from a printer. Digital or Matchprint. They haven't specified any proofing set up.