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  • Dot Gain Curve Staccato

    Can anyone point me to a site that has information on approximate dot gain and recommended calibration curves for Staccato screening?


    This is my first post and I am hoping someone here might be able to give me some valuable feedback. I am currently trying to make a harmony calibration curve for staccato 25 dot. I have requested we have the press fingerprinted for the staccato and conventional screening so that we can have two sets of plate curves.

    At this time I am not going to get what I need and will have to build some curves using my best guess. We have produced several jobs using the conventional screenings calibration curve and had reasonable results. I would like to adjust them further and was hoping for a little input from others who are using FM screening.

    If anyone can point me in the right direction to find this information or compare my curves with what others are using it would be greatly appreciated.


    thanks,
    Jon

  • #2
    Re: Dot Gain Curve Staccato

    Hi Jin,

    There is a G7 site which lists the info you may require (google it)but its for conventional AM screening not FM although you should aim to get the same dot gain values for each sets on the printed sheet, i think that the FM screen will require a harsher curve to achieve this. we aim for a about 15% gain on a 50% tint for C,M,Y and a bit more for the K 18% on coated stock running at standard weights (sheetfed offset)

    In your post you say you achieved reasonable results with your AM curve, what are you aiming for? do you have an inhouse standard or do you use G7 or ISO as a aim point? You are right when using two seperate curves for AM and FM and these curves should give the same dot gain values on the sheet irespective of the screening.

    When i ran linear plates with stacato i was in the 22 to 25% region of dot gain in the mid areas compared with 12 to 16% with an AM linear set. Hence the reason for two sets of curves.

    Hope this help Paul

    Comment


    • #3
      Re: Dot Gain Curve Staccato

      Hi Jin,

      In order to get match between AM and FM, you absolutely need to fingerprint the press. AM and FM have a quite different curve shape, specially in the 3/4 tone.
      It is doable very easily with the right tools (PerfX Press Curves™).

      It is possible to make AM and FM to match each other with different plate curves. But you need to measure and calculate curves in order to get gray balance match one to the other. Some will say it is not possible. I can tell you that it is possible and have made it many time.

      The right curve calculation tool, QC, press fingerprint. That is what you need. If one element is missing, forget about matching AM and FM each other.

      Hope this help!

      Louis Dery
      TGLC inc.

      Comment


      • #4
        Re: Dot Gain Curve Staccato

        You should be able to find this info on the Kodak customer tech website: https://ecentral.creo.com/

        If you are going to do this yourself - very briefly the basic process is as follows:
        1) You must have a stable consistent print process with your current AM screening. You cannot build plate curves for an unstable process.
        2) Your current AM printing is considered your "target" - the tonal response that you will align Staccato to
        3) You run an AM press sheet to your current SIDs using whaever curves you currently use.
        4) You then run uncalibrated plates - no curves - with Staccato at the same SIDs.
        5) You measure the dot gains/tonal response of your AM press sheet taken from tone scale step wedges in your test form - 0% to 100%
        6) You measure the dot gains/tonal response of your Staccato press sheet taken from tone scale step wedges in your test form - 0% to 100%. This is your "current" press tonal response.
        7) You enter the "target" values and "current" values into Harmony which then calculates the appropriate tone value compensation curve.
        8) You go back on press with the Staccato screened plates run to the same SIDs
        9) You measure and confirm that you got the same tone response as your target AM press sheet.
        10) You check the gray balance of your Staccato press sheet against the gray balance of your AM target sheet
        11) Make any minor adjustments as required.
        12) Your done.

        Three key things:
        1) Use a test form that only has tone ramps and scales - NO images or proofs. The press operator's job is to hit the SIDs across and around the sheet so that you get good data. Pictures and proofs will just confuse the press operator.
        2) You must have a stable consistent print process with your current AM screening. You cannot build plate curves for an unstable process.
        3) You will achieve a tonal match, however, you may not achieve a color match in one and two color screen tint builds. Staccato will likely deliver a slightly larger chroma in screen tint builds than your current AM.

        Contact me offline if you need more info.

        best, gordo

        Comment


        • #5
          Re: Dot Gain Curve Staccato

          Thanks for the responses.

          I plan to follow the information attached and do the best we can. Unfortunately the press room is not allowing me the time and budget to do all of the testing needed up front. Wish me luck.

          Is anyone running both screening types on a single press? I would be very interested to know how the curves vary between the two. It would be very helpful if I could see the two different curve shapes so I could better understand how staccato gains.

          My company is not interested in doing this the correct way at this time so I am going to tweak a few curves using a best guess as to how they might gain and see how the jobs print. Hopefully we will be able to do this the correct way in the near future but I have been saying that for several months now!

          thanks again,
          Jin

          Comment


          • #6
            Re: Dot Gain Curve Staccato

            Jim - the plate curve numbers to give curve A on ISO = 50% =64%

            20 MICRON

            10 = 5
            20 =12
            30 =19
            40=26
            50=32
            60=39
            70=47
            80=59
            90=73

            I am a B2 vcolour house - we have no problems running different curves -

            Peter

            Comment


            • #7
              Re: Dot Gain Curve Staccato

              Peter's values are nearly identical (within 1-2% through out) to curves I recently created for a new ink set using G7 with 20 micron stochastic. A different ink set with the same screening and paper resulted in about an 8% difference to those values.

              Comment


              • #8
                Re: Dot Gain Curve Staccato

                Thanks for the responses and the numbers provided. I compared them to the current curves we are using and they are fairly close all within a percent or two. We are cutting back less at the high and low end currently but at least I know we are in a similiar place to what other people are doing.

                Im gonna start some test based on what has been suggested and try to convince the company to invest in a densitometer so I can get some accurate data to work with!

                thanks again for all your help!

                Comment


                • #9
                  I had been running Staccato (linear) and compare it with my AM print (with curve) and found that it is 'patchy' in Staccato screening. I had been running on constant printing pressure as AM. What can i do to eliminate the 'patchy'.

                  Comment

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