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  1. #1
    Savage is offline Junior Member
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    Default Agfa Amigo and 20 micron FM screening

    We did some FM tests on our current setup. Our workflow currently only has 20 micron FM available. Our Amigo plates technical info says it only goes down to 25 micron. We did a TVI profile for FM, and used the NPscreen profiles from ECI.
    The results weren't good. We couldn't match our certified proof, all the images were lacking contrast, and there was an overall random color shift in the images, despite all the densities were controlled and stable.
    I was expecting problems in the lighter areas, and possibly some loss of detail all around. I was not expecting color shift and contrast problems.
    Could this be caused by the plate not being up to spec with our FM screen, our that would not explain the results.
    Can someone help me understand what went wrong? Thank you.

  2. #2
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    VladCanada is offline Senior Member
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    <<Resolution 1-99% with :Sublima 240, 200 lpi. 25μ FM>>

    Your Tech was right; do not expect a miracle from plates working out of spec.
    That minimum of 25μ dot size - because of thermofuse technology.
    Last edited by VladCanada; 02-01-2011 at 11:03 AM.

  3. #3
    gordo's Avatar
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    Quote Originally Posted by VladCanada View Post
    <<Resolution 1-99% with :Sublima 240, 200 lpi. 25μ FM>>

    Your Tech was right; do not expect a miracle from plate working out of spec.
    That minimum of 25μ dot size - besause of thermofuse technology.
    Just to expand a bit on the issue.

    Typically a 20 micron FM screen will use 20 micron dots (4 10.6 micron pixels) up until about the 30% tone. At about 30% the dot size begins to grow to 25 microns. So, from 1%-30% and 70%-99% the size of the dots that make up the screen are out of spec for your plate. Those tones will be unstable and inconsistently rendered on plate and hence will not be reliable on press. That can cause color shifts.

    An inability to match an existing proof that is based on an AM/XM screen is a separate issue. The small dots and their distribution means that, for the same tone value on press, and FM screen will exhibit a higher chroma. Hence for the same tone value on press the color will be different.

    Contrast problems can be caused by incorrect tone reproduction curves being applied to the plates or it can be caused by poor ink transfer, or poor ink performance with the microdots that make up an FM screen.

    If your workflow currently only has 20 micron FM available, I would suggest that you speak to your vendor. It is likely that other (larger) screen dot sizes are available. Perhaps you can persuade them to give you a (free) trial license for a coarser screen in order to evaluate its suitability for your shop.

    hope that helps, gordon p

  4. #4
    Savage is offline Junior Member
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    Thank you both for your answers.
    @gordo: I think you gave a very good explanation on what may have caused both the color shifts and the lack of contrast. Just for the record, i knew we could't match an FM screen with an AM/XM screen, thats why we did our tests against a certified proof calibrated to fogra43, so if nothing went wrong, it should have matched.
    As for your suggestion, i will try it. If if fails i will talk to a plate vendor to get a couple of boxes of some plate that can do 20 microns. It will be a bigger pain to setup, but i'm willing to give it a go.
    Again, thank you very much.

  5. #5
    gordo's Avatar
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    Quote Originally Posted by Savage View Post
    [SNIP]Just for the record, i knew we could't match an FM screen with an AM/XM screen, thats why we did our tests against a certified proof calibrated to fogra43, so if nothing went wrong, it should have matched.[SNIP]
    It is unfortunate that, AFAIK, Fogra characterization data is based on linear film (!) - although, as is typical with ISO/Fogra documentation, they are not really clear on this basic issue. You might suppose that with CtP you should run linear - despite the fact that linear film does not deliver linear plates. But that's another discussion.

    Because of this 1970s mentality of linear film as the standard, Fogra 43 as your target for color will probably mean that your presswork will run very dark due to the higher dot gains compared to your Fogra 39. Does your current proofing show this? i.e. Fogra 39 (I assume) proof vs Fogra 43 proof.

    BTW, I haven't been able to find the Fogra 39 and 43 profiles ( I would sure appreciate it if someone sent me their copies at pritchardgordon @ gmail (dot) com )

    best, gordon p
    Last edited by gordo; 01-28-2011 at 01:29 PM.

  6. #6
    maas is offline Senior Member
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    We are about to undertake a similar test, on newsprint using a Goss HT70 press.

    We have Agfa Polaris platelines and Harlequin 8 rips, currently we produce 10000 plates per week at 200 per hour, our Agfa representative tried to push the Sublima xm sceening solutions stating the FM screening at 25 uM ( 1880 dpi) would reduce the 200 plates per hour to 80, i have read several reports which claim little or no loss of Ripping or imaging speed, any feedback would be appreciated

    regards
    Maas

  7. #7
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    maas:

    What lpi and resolution are you imaging at now?
    Steve Musselman, Agfa Graphics - USA,
    Senior Corporate Account Executive

  8. #8
    gordo's Avatar
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    Quote Originally Posted by maas View Post
    our Agfa representative tried to push the Sublima xm sceening solutions
    What lpi screening are you using now? What lpi XM screening is your representative suggesting? Why are you thinking of changing screening?

    best, gordon p

  9. #9
    maas is offline Senior Member
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    Gents I stand corrected, we were running 200 plates per hour at 100lpi/1016 DPI, we changed to 110LPI/1270DPI and run 185 plates per hour.

    The project is currently at its infancy and first and foremost we want our vendors to be on board, my initial opraoch to Agfa was along the lines of " we wish to test the potential of FM screening , is this feasable on our current Agfa equipment and plates" the response was somewhat vague and heavily geared towards an FM/AM solution (Sublima) to compensate for the issue ocasianaly seen in flat tints in FMscreening. ( but then conventional screening also has issues in midones)

    Our focus is to test FM screening, and therefore we would not consider a AM/FM solution at this stage


    The reason which we want to test FM screening is due to the very real benifits in terms of quality reproduction, ink saving etc

    regards
    Maas

  10. #10
    gordo's Avatar
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    @Maas For newspaper work, the most used FM dot size is 35 micron. On a 1016 DPI device that's a highlight dot size of about 30 microns (~2% dot at 110 lpi) and a ~43 micron midtone dot. I believe that with your Harlequin RIP that's the HDS Coarse screen (check your documentation). That appears to be within your output device's specification. Agfa should be able to confirm whether that is within specification and tell you whether they will support it or not.

    best, gordon p


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