18 Replies Latest reply on Mar 6, 2012 4:19 AM by Stormcloud492

    What’s Black & White & Gray All Over?

    Stormcloud492

      I’m trying to become a pre-press expert after an embarrassing error on a job I sent to print last Spring. All the gray initial caps, lines and text boxes of the 12-page newsletter failed to print. Bottom line, I sent the job to this budget printer without converting from RGB to CMYK, because the printer had requested it for the previous issue.  The printer ate the cost of reprinting about 200 of the newsletters (presumably because they felt they shared responsibility for the error).  What’s clear is that I can’t count on guidance from this printer.

       

      The other thing you should know is I am a freelancer, an American working in Germany, and have no direct communication with the printer – the client is the intermediary. I’m using Adobe Indesign CS4 ver. 6.0.6, on a MacbookPro OSX 10.6.8.  Now the next issue of the newsletter is coming my way.

       

      The 12-page brochure is printed as follows:

      front and back cover on coated stock in 4-color,

      inside front and back cover on coated stock in B&W,

      and interior 8 pages in B&W on uncoated stock.

       

      There was no problem printing the previous issue, apart from poor quality B&W photos and grayscale elements in the interior pages. The only difference in the manner in which I submitted the second job was that I “converted” the photos using Layer Effects into the appearance of B&W, so I could better visualize how they would convert to grayscale (they remained in RBG color space).

       

      All I can conclude is that when the printer saw the B&W photos, he assumed that I had actually converted everything in the interior pages to grayscale and therefore didn’t check for the presence of RGB color space. The gray text, box and line elements that were in RGB converted to equal amounts of CMY, which translated to white and thus dropped out of the plate! I should have known that this was a risk, but I did not.

       

      Help me, if you will, understand what good practices will avert such an error in the future. I have now read many good resources on pre-press, and I think I now understand, but need reassurance that I’m on the right track.

       

      The newletter will be printed, but will also be linked to a website for online viewing as well as distributed in a lo-res version as an email attachment. So, I’m trying to understand what my workflow should be.

       

      Should I work in an RGB workflow until the client approves the artwork, then output (a) using the PDF standard for CMYK offset printing to generate the version to send to the printer ; (b) then output another file using the PDF standard for Web; and finally another using “smallest file size” for email distribution?

       

      In other words, should none of the color conversions should be done in the native Photoshop files or in InDesign, rather they should take place during PDF conversion using an appropriate standard? Or should I convert in Photoshop all the images to be used in the interior pages to grayscale images and all the images to be used on the front and back cover to CMYK before creating the PDF?  This, of course, would require making two sets of images, one for the print version, and the other for Web display.

       

      Should I work with vector and type images in CMYK from the very start and keep my palette strictly in CMYK mode? Or should I work entirely in RGB and allow them to be converted to grayscale via PDF conversion?

       

      There is the related issue of using both coated vs. uncoated stock, which the client wants to keep costs down. The interior black and white pages on uncoated stock gave less than satisfactory results in the first two newsletters. Despite my efforts to improve and lighten the photos in Photoshop, most of the values printed much darker and less sharp than the photos on the coated stock. The values of the two-tone grays in the (vector) banner were dramatically different when viewed side-by-side on pages 2 and 3 and pages 10 and 11.

       

      Can you produce one PDF that has two different output intents -- coated stock for pages 1, 2, 11 and 12; and uncoated stock for pages 3 through 10?  Would this solve the problem, or is there something in addition that I should be doing with “Dot Gain” in my prepress that would solve this problem?

       

      Here are some assumptions I’ve made so far, after gleaning information from various sources:

      1. I have set my Adobe Bridge color setting preferences to Europe General Purpose 2 for screen and print.
      2. I am assuming I should use an RGB workflow until the last moment before submission to the printer (to preserve flexibility and enable output for muliple purposes, e.g., print and Web versious).
      3. I should ascertain from the printer which standard of PDF is compatible with his RIP and would give him the most flexibility to make adjustments for his RIP so we get the best printing results.
      4. I should choose a Preflight Profile, such as the VIGC Live Preflight Profiles (Ghent PDF Workgroup) to identify any potential compliance problems with color space, transparency, overset text, bad fonts, cropping, etc. prior to conversion to a PDF.

       

      Any advice you could offer would be appreciated.

        • 1. Re: What’s Black & White & Gray All Over?
          rob day Adobe Community Professional & MVP

          You can leave RGB images in your layout and let the conversion to CMYK happen on export—the CMYK values output will depend on the destination profile you choose in the export dialog. Assuming you use the same profiles there is no difference between a Photoshop and Export conversion.

           

          As you have discovered you can't get neutral RGB images to convert to grayscale on Export—the conversion is to CMYK and most CMYK profiles convert neutral RGB values to a mix of all 4 CMYK colors. If you want grayscale in the layout you'll need to place grayscale.

           

          Can you produce one PDF that has two different output intents -- coated stock for pages 1, 2, 11 and 12; and uncoated stock for pages 3 through 10?  Would this solve the problem, or is there something in addition that I should be doing with “Dot Gain” in my prepress that would solve this problem?

           

          No. When you export or print there can only be one destination so if you want to color manage correctly you'll need to set up two different documents, one profiled for a coated sheet and the other profiled for uncoated. You can export without any conversions (PDF/X-4), but when the PDF is output everything still gets converted to one destination CMYK profile.

          1 person found this helpful
          • 2. Re: What’s Black & White & Gray All Over?
            Peter Spier Most Valuable Participant (Moderator)

            rob day wrote:

             

            As you have discovered you can't get neutral RGB images to convert to grayscale on Export—the conversion is to CMYK and most CMYK profiles convert neutral RGB values to a mix of all 4 CMYK colors. If you want grayscale in the layout you'll need to place grayscale.

             

            While the B&W adjustment layer doesn't work in RGB to give you grayscale, I believe it DOES work if the images are CMYK, which means you can use an adjustment layer and ID's layer visibility to toggle output between CMYK and grayscale (well black ink only of the CMYK) without having to have two images. Thatmight be useful if you were going to press, but probably not for this.

            • 3. Re: What’s Black & White & Gray All Over?
              rob day Adobe Community Professional & MVP

              By B&W adjustment layer you mean Photoshop's Black & White... right? In my CS5 it's grayed out for CMYK  images.

              • 4. Re: What’s Black & White & Gray All Over?
                Peter Spier Most Valuable Participant (Moderator)

                rob day wrote:

                 

                By B&W adjustment layer you mean Photoshop's Black & White... right? In my CS5 it's grayed out for CMYK  images.

                Well, I did, but I looked up the old discussion on another list and found I misremembered. You use a Channel Mixer layer set to monochrome in Photoshop on a CMYK image. Who'd have thought?

                • 5. Re: What’s Black & White & Gray All Over?
                  Stormcloud492 Level 1

                  Hi Rob -- thanks for your comments. Would a printer accept this two-PDF solution to the problem? Would he be able to "slice and dice" the PDFs to create his plates?

                   

                  Do you think this would solve the problem of the  B&W images and banner printing darker and fuzzier on the uncoated stock? Or is there something I need to learn about "dot gain" too?

                   

                  rob day wrote:

                   

                  You can leave RGB images in your layout and let the conversion to CMYK happen on export—the CMYK values output will depend on the destination profile you choose in the export dialog. Assuming you use the same profiles there is no difference between a Photoshop and Export conversion.

                   

                  As you have discovered you can't get neutral RGB images to convert to grayscale on Export—the conversion is to CMYK and most CMYK profiles convert neutral RGB values to a mix of all 4 CMYK colors. If you want grayscale in the layout you'll need to place grayscale.

                   

                  Can you produce one PDF that has two different output intents -- coated stock for pages 1, 2, 11 and 12; and uncoated stock for pages 3 through 10?  Would this solve the problem, or is there something in addition that I should be doing with “Dot Gain” in my prepress that would solve this problem?

                   

                  No. When you export or print there can only be one destination so if you want to color manage correctly you'll need to set up two different documents, one profiled for a coated sheet and the other profiled for uncoated. You can export without any conversions (PDF/X-4), but when the PDF is output everything still gets converted to one destination CMYK profile.

                  1 person found this helpful
                  • 6. Re: What’s Black & White & Gray All Over?
                    Stormcloud492 Level 1

                    Hi Peter, do I understand you correctly, that I should convert all the images on the interior pages to grayscale in Photoshop prior to placing them in InDesign?

                     

                    So my workflow requires two sets of images: RGB photos for pages 1 and 12 and grayscale images for pages 2 through 11?

                     

                    Then I have to create two PDFs: one for pages 1, 2 and 11, 12, with an output intent of CMYK offset print on coated stock,

                    and the other for pages 3 through 10, with an output intent of CMYK offset print on uncoated stock?

                     

                    The printer, for the previous issue, had requested I leave all images in RGB. Should I just change the output intent for pages 3 through 10 to uncoated stock?

                     

                    Also, for the web version, I would create a document with all RGB images and create a PDF with an output intent of RGB?

                     

                    I'm still not clear whether this 2-PDF approach solves the problem of dark and poor image quality on the pages printed on uncoated stock, or whether I need to learn something about dot gain.

                     

                    Thanks for taking your time to comment -- it's really helpful. I hope my questions are clear enough.

                     

                     

                    Peter Spier wrote:

                     

                    rob day wrote:

                     

                    As you have discovered you can't get neutral RGB images to convert to grayscale on Export—the conversion is to CMYK and most CMYK profiles convert neutral RGB values to a mix of all 4 CMYK colors. If you want grayscale in the layout you'll need to place grayscale.

                     

                    While the B&W adjustment layer doesn't work in RGB to give you grayscale, I believe it DOES work if the images are CMYK, which means you can use an adjustment layer and ID's layer visibility to toggle output between CMYK and grayscale (well black ink only of the CMYK) without having to have two images. Thatmight be useful if you were going to press, but probably not for this.

                    • 7. Re: What’s Black & White & Gray All Over?
                      Toi B

                      Yes, images to be printed in black should be converted to grayscale before placing in indesign.

                       

                       

                      If you were to submit color photos in rgb, then you wouldn't have to worry about paper stock. The printer can extract pages and convert them to cmyk according to their workflow.

                       

                       

                      But if you were to submit them in cmyk, then you would need two pdf files. One for the coated pages, another for the uncoated.

                       

                       

                      For the web version, you don't have to create another indesign document. I believe you can set a 'convert to rgb destination' option during pdf export.

                       

                      And yes, we all have to learn something about dot gain. I believe you just did, the hard way

                      • 8. Re: What’s Black & White & Gray All Over?
                        rob day Adobe Community Professional & MVP

                        Grayscales are output from InDesign unchanged to the black CMYK plate. Their preview can change when Overprint or Separation preview are turned on (depending on the document's assigned CMYK profile) but the output numbers do not change.

                         

                        In Photoshop there is a grayscale space and a grayscale's preview depends on the assigned grayscale profile, or the Gray Working Space in Color Settings if there's no assignment. Changing or assigning a different grayscale profile doesn't change the output numbers—just the preview. So if your grayscales are printing too dark increasing the dot gain profile to 25 or 30% will give you a darker preview for the same values and you can color correct from there. You might also consider an exaggerated Unsharp Mask for uncoated to fight the softness.

                         

                        ID ignores grayscale profiles so if your interior uncoated signature is all grayscale, you don't need to export two different PDFs—however they might preview too light if you color corrected the grayscales using a 30% Dot Gain in PS.

                        • 9. Re: What’s Black & White & Gray All Over?
                          Peter Spier Most Valuable Participant (Moderator)

                          What Rob says is correct, but I think in this case, since the job is, I think, going on press and printing on two different stocks, I would probably prepare separate files for the color on coated stock and the K-only on uncoated, but ask the printer. All questions about how they really want to receive your material should be addressed to them.

                          • 10. Re: What’s Black & White & Gray All Over?
                            Grant H Level 4

                            I would export the (to be converted) pages to PDF, and acrobat convert it. If the settings are correct and conversion profile correct (dot gains etc), it does a good job.

                             

                            And send the printer 2 files.

                             

                            G

                            • 11. Re: What’s Black & White & Gray All Over?
                              Stormcloud492 Level 1

                              rob day wrote:

                               

                              Grayscales are output from InDesign unchanged to the black CMYK plate. Their preview can change when Overprint or Separation preview are turned on (depending on the document's assigned CMYK profile) but the output numbers do not change.

                               

                              In Photoshop there is a grayscale space and a grayscale's preview depends on the assigned grayscale profile, or the Gray Working Space in Color Settings if there's no assignment. Changing or assigning a different grayscale profile doesn't change the output numbers—just the preview. So if your grayscales are printing too dark increasing the dot gain profile to 25 or 30% will give you a darker preview for the same values and you can color correct from there. You might also consider an exaggerated Unsharp Mask for uncoated to fight the softness.

                               

                              ID ignores grayscale profiles so if your interior uncoated signature is all grayscale, you don't need to export two different PDFs—however they might preview too light if you color corrected the grayscales using a 30% Dot Gain in PS.

                              So, I'm back -- been working on layout issues, but now with presstime approaching, must turn to pre-press issues. I'm woefully unprepared. All your answers are helpful and I have added many resources gleaned from Layers Mag, Sandee Cohen, Smashing Magazine, etc. No one source lays out a clear workflow. Maybe everyone just assumes a higher level of basic knowledge than I have to date?  I need more of a "step-by-step" approach, an explanation of the correct workflow. Here is how I'm approaching it at this point:

                               

                              1. Image Correction -- Many of the the RGB photos that I've placed in InDesign are too dark, and I know from the last two printings that they will be even darker when printed on uncoated stock in B&W. I will first adjust (in Photoshope) these RGB photos until they seem correct to the eye, before converting them to Grayscale. I am assuming it is easier to see while the image still retains its color data.

                               

                              2. Conversion to grayscale -- I will convert the RGB images (in Photoshop) to Grayscale. After the color data is lost, I will further adjust the images in Photoshop using Levels or Brightness & Contrast until they appear correct to the eye.

                               

                              3. Unsharp Mask -- I will sharpen the B&W images (in Photoshop) to counter the effects of dot gain.

                               

                              4. PDF preparation -- I will export the Grayscale pages to a separate PDF with an output intention of Uncoated Stock. Is there an ICC Profile for grayscale printing on uncoated stock?

                               

                              So, I'm left with many questions, but a couple come to the foreground after reading your post:

                               

                              -- Do I attempt to adjust for dot gain in Photoshop prior to placing in InDesign, or do I just correct the tonal values to the best of my ability in Photoshop?

                               

                              -- Does the choice of an ICC Profile of printing on uncoated stock have a "built-in" correction for dot gain? So, if I compensated for dot gain in Photoshop, would I be "double-compensating" resulting in images that are too light?

                               

                              -- I see that Adobe Acrobat 9 has the ability to do grayscale conversions and dot-gain compensation on output -- is the better way to go, to correct the RGB images to the eye in Photoshop, then leave the job of dot-gain compensation to the PDF conversion?

                              • 12. Re: What’s Black & White & Gray All Over?
                                Stormcloud492 Level 1

                                Grant, thanks for your comment. Could you read my detailed query to Rob and tell me if I have understood you correctly? Many thanks.

                                Grant H wrote:

                                 

                                I would export the (to be converted) pages to PDF, and acrobat convert it. If the settings are correct and conversion profile correct (dot gains etc), it does a good job.

                                 

                                And send the printer 2 files.

                                 

                                G

                                • 13. Re: What’s Black & White & Gray All Over?
                                  Stormcloud492 Level 1

                                  Hi Peter, My greatest frustration is I can't communicate with the printer -- he is at a distance, has no time to speak with customers, and speaks only German. All I can think to do is inform myself as well as possible about how to professionally prepare the files, then write (and have translated) a memo outlining what I have done. At least I will have done my "due diligence" and if there are any problems with the job, the responsibility will be on him, if he does not read the memo or ask me to correct anything that does not work for his workflow. I will definitely output the job in two files, one for coated and one (K-only) for uncoated.

                                  Peter Spier wrote:

                                   

                                  What Rob says is correct, but I think in this case, since the job is, I think, going on press and printing on two different stocks, I would probably prepare separate files for the color on coated stock and the K-only on uncoated, but ask the printer. All questions about how they really want to receive your material should be addressed to them.

                                  • 14. Re: What’s Black & White & Gray All Over?
                                    rob day Adobe Community Professional & MVP

                                    -- Do I attempt to adjust for dot gain in Photoshop prior to placing in InDesign, or do I just correct the tonal values to the best of my ability in Photoshop?

                                     


                                     

                                    There has to be a conversion for profiles to have an effect. So in Photoshop a grayscale image needs to be converted to monitor RGB in order to be displayed and the image's grayscale profile is used in that conversion—50% black previews darker when the profile is Dot Gain 30% than when it's Dot Gain 20%. The output is always 50% it's your preview that changes.

                                     

                                    The grayscale profile also comes into play when you convert from RGB to grayscale. RGB 128|128|128 will convert to a lighter gray value when the destination gray profile is Dot Gain 30% than when it's Dot Gain 20%.

                                     

                                    -- Does the choice of an ICC Profile of printing on uncoated stock have a "built-in" correction for dot gain? So, if I compensated for dot gain in Photoshop, would I be "double-compensating" resulting in images that are too light?

                                     

                                    The compensation is in the grayscale display not the output.

                                     

                                    When you place a grayscale in ID its values are always output unchanged to the Black plate. Assigning different CMYK profiles to the document will have no effect on the grayscale's output. Different CMYK profiles can affect the grayscale preview in ID. When you turn on Overprint/Separation Preview the document's CMYK profile changes the grayscale preview—you get a soft proof of how the grayscale will print on the black plate of the profile destination. There's never a compensation of the output numbers.

                                    • 15. Re: What’s Black & White & Gray All Over?
                                      Toi B Level 1

                                      I cannot afford calibration gadgets, nor printer's proofs. So what i do is, if I had a previous job on the same stock, I hold the actual print (from the printing press) beside the photoshop image on my monitor. Then I adjust the brightness, contrast, & color levels on my monitor until the image somewhat matches the print. That way I have a better predictor of what my next job will look like when printed.

                                      • 16. Re: What’s Black & White & Gray All Over?
                                        rob day Adobe Community Professional & MVP

                                        That way I have a better predictor of what my next job will look like when printed.

                                         

                                        That only works if you are always going to the same printer and the press conditions and paper stock never change. It also means your monitor profile no longer matches your monitor conditions—if the OP did that for his grayscales, his CMYK profiles wouldn't soft proof color images correctly.

                                         

                                        For grayscale work you could make a custom dot gain curve via visual comparison, which wouldn't compromise the monitor profile. The dot gain curve adjusts the grayscale preview without affecting the output numbers or monitor display/profile:

                                         

                                        Screen shot 2011-11-04 at 6.26.18 AM.png

                                         

                                        Screen shot 2011-11-04 at 6.26.45 AM.png

                                        • 17. Re: What’s Black & White & Gray All Over?
                                          Toi B Level 1

                                          thanks! that's exactly what i needed

                                          • 18. Re: What’s Black & White & Gray All Over?
                                            Stormcloud492 Level 1

                                            Thanks to everyone for their comments, and apologies for not giving you feedback on the resolution of the issue (I ended up in the hospital for 10 days!)

                                             

                                            I recommended to the client that they ante up a little more money and buy coated stock for all 12 pages of the newsletter, instead of only the front and back cover. The inside pages remained in B&W, with color on pages 3-11. The paper absorbed the ink uniformly on all pages, which made the client very happy. No more fuzzy, muddy blacks. And I was spared having to jump through loops to learn dot gain. Maybe this was an opportunity missed! There's always another time!