16 Replies Latest reply on Jun 13, 2014 7:42 AM by rob day

    16-bit color depth for gradients?

    jeffreych

      Hello,

       

      I have created gradient backgrounds inside of inDesign CS6 but see some color banding in offset printer's color proofs. Is there a setting/option to set inDesign to generate its color gradients at 16-bit color depth?

       

      Thanks in advance.

       

      Jeffrey

        • 1. Re: 16-bit color depth for gradients?
          Steve Werner Adobe Community Professional & MVP

          How did you supply files to the printer? As an InDesign file? As a PDF file? If a PDF file, what PDF preset did you use?

           

          Have you talked to the printer about the problem?

          • 2. Re: 16-bit color depth for gradients?
            Jeffrey_Smith Most Valuable Participant

            A gradient made from the gradient panel will not be rasterized, and therefore not have any bit depth. A frame applied with a gradient feather can have 2 outcomes on export. If transparency is not flattened, then the frame fill will have axial shading. If the transparent element is flattened, then the gradient is rasterized at 8 bit. And as far as I know, no way to control the bit depth.

             

            To reduce unwanted banding, it would be best handled by re-creating the effect in Photoshop, and adding noise. Using a 16-bit image would most likely not help the banding.

            • 3. Re: 16-bit color depth for gradients?
              jeffreych Level 1

              @Steve and @Jeffrey,

               

              Thanks for the quick responses. The files are being delivery as inDesign and collected assets (linked), not as PDF. We've worked with this printer for years and they've (always) recommended adding blur and noise to the gradients, which have been exported as EPS file and modified in Photoshop. These files open in 8-bit color mode, so I assumed it's being rasterized at 8-bit out of inDesign. I was just wanting to eliminate one more variable of any color banding possibilty by starting with 16-bit color gradients, without having to recreate all backgrounds at 16-bit in PS.

               

              @Jeffrey: When you wrote,"If transparency is not flattened, then the frame fill will have axial shading" - does this mean it's not rasterized on export? I Did a test exporting a simple gradient using the gradient swatch tool and opened the EPS file in Illustrator, but the gradient came in as a rasterized image. Maybe it's not rasterized if left in place in delivered inDesign file? Is this documented anywhere?

               

              I've been working with Photoshop for over 16 years and by everything I've read and learned about 8-bit vs 16-bit color depth, the higher bit depth directly affects gradient smoothness as there are more values to render between white and black of each color channel, no?

               

              Again, thanks for the quick and intelligent replies.

               

              Jeffrey

              • 4. Re: 16-bit color depth for gradients?
                Jeffrey_Smith Most Valuable Participant

                With my example, I should have said exporting to PDF. You are correct, when you export .eps from Indesign, both the gradient and frame with a gradient feather are rasterized.


                I will not disagree that a 16-bit gradient "displays" smoother than an 8-bit image. However, any discernible quality difference will be lost in the conversion to halftone screening for offset printing.

                • 5. Re: 16-bit color depth for gradients?
                  rob day Adobe Community Professional & MVP

                  but see some color banding in offset printer's color proofs.

                   

                  These are digital proofs (not film or press proofs)? Maybe the problem is with the proofer?

                   

                  ID doesn't support 16-bit. You can see that by placing a 16-bit image in ID, exporting to PDF/X and checking the image in Acrobat via Output Preview's Object Inspector.

                   

                  Are the gradients built with document CMYK colors and are you exporting that way? Color conversions can cause banding.

                  • 6. Re: 16-bit color depth for gradients?
                    Willi Adelberger Most Valuable Participant

                    The color depth will not solve the banding.

                     

                    But you write you export as EPS.

                    Please, don't use EPSor any other type of PostScript for new files in any case! Not to import, not to export, not to print.

                    When you need something in another application to open or to place, either in InDesign or in Photoshop or in Illustrator (don't open a non-AI-PDF there) export as PDF/X-4, not as any transparency flattened file type like EPS nor PDF1.3 and below nor PDF/X-1a or X-3

                    • 7. Re: 16-bit color depth for gradients?
                      Jeffrey_Smith Most Valuable Participant

                      Please, don't use EPSor any other type of PostScript for new files in any case!

                      Willi, without knowing the particulars of a situation, you can not make this blanket statement!

                      • 8. Re: 16-bit color depth for gradients?
                        Willi Adelberger Most Valuable Participant

                        Jeffrey_Smith wrote:

                         

                        Please, don't use EPSor any other type of PostScript for new files in any case!

                        Willi, without knowing the particulars of a situation, you can not make this blanket statement!

                        Why not? There is definitively no reason to create new stuff in EPS. Can you describe one reason, when you work inside the CC or CS where EPS makes sense or is better over the use of PDF? Not even one fact is given of the superiority of EPS. The other way round: USE PDF.

                        And the particularity was mentioned above: To open in Photoshop. This limits the use of EPS to a no go.

                        • 9. Re: 16-bit color depth for gradients?
                          rob day Adobe Community Professional & MVP

                          I have created gradient backgrounds inside of inDesign CS6 but see some color banding in offset printer's color proofs...

                           

                          In your first post you are saying the gradients are made in ID. Are you saying you were seeing banding in native ID gradients on press and are trying to solve the problem by exporting the gradients to Photoshop? Or, have you always assumed PS generated gradients would be better and never sent ID gradients to press?

                           

                          Can you post one of the problem PS gradients?

                           

                           

                          I've been working with Photoshop for over 16 years and by everything I've read and learned about 8-bit vs 16-bit color depth, the higher bit depth directly affects gradient smoothness as there are more values to render between white and black of each color channel, no?

                           

                          The reason for 16-bit mode in PS is for editing—it's highly unlikely a press is capable of printing 256 distinct gray levels never mind 16 bits' 65,536.

                           

                          If you edit in 16-bit you won't get the gray level gaps in the histogram, which could happen with repeated color corrections to an 8-bit channel. But if you start with 8-bits and convert to 16-bits the advantage is lost because the converted 16-bit file is starting with the original max of 256 distinct levels and they'll just get moved around when you edit.

                           

                          In the case you are describing converting 8-bit to 16-bit does nothing and might even make things worse.

                          • 10. Re: 16-bit color depth for gradients?
                            rob day Adobe Community Professional & MVP

                            Here's an extreme illustration where I've posterized an 8-bit grayscale gradient to 20 gray levels, duplicated the gradient and upsampled to 16-bit. If I make a curve correction to the 16-bit file no new gray levels are introduced I still only have 20 gray levels—they've just been moved:

                             

                            Screen Shot 2014-06-12 at 4.34.17 PM.png

                            • 11. Re: 16-bit color depth for gradients?
                              jeffreych Level 1

                              Hi all,

                               

                              I was away from my computer this afternoon but truly appreciate the response and dialogue from everyone. Here's a collection of replies to the various questions posted, forgive me if I don't reply to each and every one:

                               

                              1. I do not see banding on my display inbInDesign app.

                              2. I do not up-res any files from 8-bit to 16-bit as I know this only converts a rasterized 8-bit and does not add any fidelity to the original gradient.

                              3. Yes, color banding might be caused by the limitations of the halftone screen conversion, but again I want to rule out  the possibility of banding from the digital file by providing the highest quality asset files to my printer - at least for this job where the gradients are high key values - tints gradating to white or zero opacity - which seems to show banding more readily than darker or mid value gradients.

                              4. BTW I should get an answer from our printer rep tomorrow regarding if they think 16-bit grad files would be helpful.

                              5. Color space of all files in and out of InDesign is only CMYK, so banding from converting color space is not present.

                              6. Color proofs are high-quality digital prints which shouldn't show any more banding than an offset printer with lower dpi than proof printer, no?

                               

                              Thank for your helpful contributions. I'll let you know what our printer reports back.

                               

                              Jeffrey

                              • 12. Re: 16-bit color depth for gradients?
                                rob day Adobe Community Professional & MVP

                                the gradients, which have been exported as EPS file and modified in Photoshop. These files open in 8-bit color mode, so I assumed it's being rasterized at 8-bit out of inDesign. I was just wanting to eliminate one more variable of any color banding possibilty by starting with 16-bit color gradients, without having to recreate all backgrounds at 16-bit in PS.

                                 

                                 

                                2. I do not up-res any files from 8-bit to 16-bit

                                 

                                Your InDesign to EPS to Photoshop 16-bit workflow would have to have an upsample to 16-bit—exported EPS from ID to PS is 8-bit.

                                 

                                6. Color proofs are high-quality digital prints which shouldn't show any more banding than an offset printer

                                 

                                I don't think that's guaranteed—a digital proof could use a different screening, i.e., a stochastic screen rather than a halftone screen.

                                • 13. Re: 16-bit color depth for gradients?
                                  jeffreych Level 1

                                  Rob,

                                   

                                  As I noted in point number 2, I never up-res'd from 8-bit to 16-bit, but was wondering, hoping, if there was any option to export internally generated  gradients from InDesign as 16-bit instead of 8-bit. It appears that's not possible.

                                   

                                  I'll try to find out more details about the proofing printer and screen conversion printer uses.

                                   

                                  Thanks for your input.

                                  • 14. Re: 16-bit color depth for gradients?
                                    Danny Whitehead. Level 4

                                    Are they native InDesign gradients or have they been rasterised in Photoshop and placed back into ID?

                                     

                                    What are the values of the banding gradients?

                                     

                                    Possibly the most common output setting for a platesettter is a 150lpi line screen at 2540dpi resolution. That yields 256 levels of grey per channel, i.e. 8-bit colour. So with only 256 levels of grey, very subtle gradients over a large area will be prone to banding.

                                     

                                    Then you have the additional problem of dot gain, which makes gradients to white particularly troublesome. It's difficult to print an actual 1% dot. The nature of ink on paper will expand a 1% dot in your file and on the plate to maybe a 5% dot on paper, so there will be a noticeable drop-off.

                                    • 15. Re: 16-bit color depth for gradients?
                                      Jeffrey_Smith Most Valuable Participant

                                      but was wondering, hoping, if there was any option to export internally generated  gradients from InDesign as 16-bit

                                      by exporting to pdf first, which will not rasterize the gradient up to this point. Then open and rasterize in Photoshop, where you can specify both the resolution and bit depth.

                                      • 16. Re: 16-bit color depth for gradients?
                                        rob day Adobe Community Professional & MVP

                                        Then open and rasterize in Photoshop, where you can specify both the resolution and bit depth.

                                         

                                        Jeffery, It seems like that should work, but if you look closely at the histograms it doesn't look like you get 16-bits of gray levels. Here's a black to white blend exported to PDF/X-4 and opened as 8 and 16 bit CMYK. The black channel histograms are the same:

                                         

                                        pdfimport.png

                                         

                                        If there were more than 256 levels of gray in the 16-bit version I should be able to make a correction without gaps showing in the histogram, but that doesn't happen:

                                         

                                        16bitCurve.png

                                         

                                        If I make the black channel blend in Photoshop I can make the same correction without gaps:

                                         

                                        PS16-bit.png

                                        PS16bitCurve.png