4-Color printing lesson for a single or 2/color press

Discussion in '1-Color and 2-Color Offset Presses' started by DanRemaley, Mar 11, 2017.

  1. DanRemaley

    DanRemaley Member

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    GCR is applied as a % (of black) replacement. Max is 100% - example:
    Take 50c/40m/40y (gray) into photoshop and convert to Max GCR - results? 50% Black!
    Med is a 50% replacement, leaving some y-m-c there.
    Standard deviation is 2% midtone gain.
    Max GCR allows for a 4% variation without changing the color!
    UCA can be applied as a % to either!
    Call anytime 412.889.7643
     
  2. emet

    emet Member

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    How much UCA does one tend to use
     
  3. DanRemaley

    DanRemaley Member

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    Depends whether coated or uncoated.
    Total Ink Coverage is around 320 for coated and 240 for uncoated.
    You apply UCA as a % but check the TIC.
     
  4. emet

    emet Member

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    I would like to have values for both.
    I will make sure I adjust TIC
     
  5. emet

    emet Member

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    What about black ink limit?
     
  6. DanRemaley

    DanRemaley Member

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    These adjustments are image dependent. You have to check TIC after you apply UCA
     
  7. emet

    emet Member

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    I am in the middle of running the press with my plates as close to linear as I could get with what I am using.
    I am thinking that I am going to measure the dot values for the chart you gave me and make an adjustment curve in photoshop. I can make a dot gain curve and create a profile or I just adjust each image with the curves function. I think I have figured out how I can do it with a dot gain curve in a custom color profile.
    I also have a question about my densitometer. I have two. One calibrates itself somehow and one I have to measure the paper and then the solid. They give quite different readings. Can you help me understand this and know which one to use
     
  8. emet

    emet Member

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    I have done 3 of the 4 colours and my measured values on the sheet with my "somewhat" linear plate are almost what you gave me. Mostly just a few percent + and -. That is with the Vipdens densitometer that you have to zero on the paper and then measure a solid before you start measuring the dot.
     
  9. DanRemaley

    DanRemaley Member

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    There should be a setting for the densitometer that is “status T”.
    The density readings should be ‘absolute’ (including paper). It should NOT subtract paper for density measurement.
     
  10. DanRemaley

    DanRemaley Member

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    Of measuring dot area or dot gain the instrument will subtract paper - that’s correct! Just don’t use the density reading for anything-
     
  11. emet

    emet Member

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    hmmm,
    one densitometer I have ONLY reads density after zeroing to paper. The other one does not.
    The first is the one I used. It has a higher reading. When it reads 1.4 the other reads .7
    Neither have been calibrated. I do have a freshly calibrated card that I tried both on. The first is fairly close to the calibration values.
     
  12. DanRemaley

    DanRemaley Member

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    You can add the paper value to the measurement i.e. (.07 paper + 1.33 reading = 1.40 density
     
  13. emet

    emet Member

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    So are you saying it is good to have as much UCA as you can without going over the recommended TIC. I think I am starting to understand.
     

  14. DanRemaley

    DanRemaley Member

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    Yes-correct! UCA is applied as a %.
    It only affects the shadow area - not highlight or mid tones.
     
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