6 Replies Latest reply on May 20, 2009 11:50 AM by Larry Tseng

    Weird dot gain chart

    Larry Tseng Level 1

      A book printer supplied overall dot gain figures for a b/w job that will print on coated stock as follows:


















      Note how the TVI increases continuously throughout the range, forming a straight line rather than a curved section when plotted as a traditional dot gain chart (see attached jpeg).

      Does anyone care to comment on this unconventional approach by the printer?


        • 1. Re: Weird dot gain chart
          Lou Dina Level 3

          Hi Larry.  It's been awhile.  Hope you are well.


          I am wondering if that is a final tweak or plate adjustment curve to hit GRACoL or SWOP targets (or their own in house target) on press.  There is no dot gain curve that I have ever seen that looks anything close to that.  A typical dot gain curve always maxes out somewhere near 50% density and always gets lower as you move toward both white and black.  US Web Coated SWOP v2 maxes out at 57%, with values of +18.5C, +17.1M, +17.1Y, +21.2K.  GRACoL G7 profile on #1 coated stock maxes out at 53%, with +13.7C, +15.7M, +16.4Y, +19.7K.


          I know those are 4/C CMYK profiles, but that is more the range I would expect.  Super high quality coated stock can sometimes end up with very low dot gains closer to 10% or 12%, but I have never seen any stock with dot gains like you are talking about (+1.5% to 2.0% at middle gray).



          • 2. Re: Weird dot gain chart
            Larry Tseng Level 1

            Hi Lou,

            Thanks for responding. Hope you are well too.

            The curve apparently shows the overall TVI. To confirm this, I posed this question to the printer:

            "A book pdf file supplied by us contains a title page with two gray patches. One patch is 50%-K and the other patch is 75%-K. When the title page is printed, the patches will come out as 51.5%-K and 77.3%-K on your coated sheet (this is how I am interpreting the figures). True or false?"

            The printer's reply: "True".

            "True" would mean supplying them b/w images converted to a near-linear profile space, with bit-depth/loss of tonal resolution becoming an issue if there is an 8-bit bottleneck in the workflow starting at our end.

            Any idea why a printer might want to operate with an near-linear overall transfer function?




            • 3. Re: Weird dot gain chart
              Lou Dina Level 3



              Had guest from out of town.  Sorry for the delay.  I do not know what they are doing.


              Can you get them to print you a sample from a known file before you run your project?



              • 4. Re: Weird dot gain chart
                Larry Tseng Level 1


                Yes, a test proof is in order. Will let you know what happens if we go through with this printer.



                • 5. Re: Weird dot gain chart
                  Lou Dina Level 3



                  Did you every resolve this?  I'd be interested to hear what you found and how it jives with what you printer is saying.



                  • 6. Re: Weird dot gain chart
                    Larry Tseng Level 1




                    I'm waiting for a replacement Agfa/Apogee Sherpa proof of a 1-color profiling chart because the first try came back missing an entire row of patches. Still, since the rest of the proof looks normal to me, at least one individual in prepress doesn't know how much gain there is from pdf to press sheet.



                    Here's what one respondent to my post at PrintPlanet had to say:






                    The same prepress manager must work at lots of other places as well, because I seem to keep running into him.