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Thread: Strange gradient problem

  1. #1
    StarDigital is offline Fiery Forum Expert Contributor StarDigital is on a distinguished path
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    Default Strange gradient problem

    Xerox 1000 color press, CWS 5.7 recently upgraded,

    I have a Business card preimposed that has a illustrator gradient for a background. When i do my normal preset setup for the paper and positioning, etc and then look at it in image viewer everything looks good. But when i print it i get horrible gradient like the rip to the machine went bad or something. Never had a problem with gradients on the 1000 color press, and i tried restarting the press and fiery both, tried composit and trapping, tried Postscripting it, and tried converting it all to cmyk all with no luck.

    Has this happened to anyone before? Is it illustrator like i'm thinking. Or could CWS 5.7 have added an error in the rip. If you want a sample message me.

    Thank you.
    dan

  2. #2
    adam1991 is offline Fiery Forum Expert Contributor adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful
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    For a flat file like you describe (by "preimposed" I presume you mean that the file you give to the Fiery is simply a large sheet that happens to have a bunch of business card images already on it), CWS has zero to do with how the RIP interacts with the source file.

    You see what looks good in Image Viewer. That shows you what the RIP is doing. Post-RIP, there are only two items: calibration and the engine.

    What you describe is a classic case of bad/improper/corrupt calibration.

    But it could also be something in the engine. Keep in mind, the Fiery sends a base raster image to the engine; the engine then has to screen it for its own purposes. You control that screen inside the Fiery job ticket; make sure that you are using the same screen you always have. Presuming you are, trust me when I say that I *have* seen a Xerox engine just suddenly stop working in this regard, giving exactly the results you describe. It was impossible to get the service organization to understand, because they didn't understand the theory of operation of the press and how the internal screening happens.

  3. #3
    StarDigital is offline Fiery Forum Expert Contributor StarDigital is on a distinguished path
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    I discovered the cause of the problem but not the reason behind it. Frankly i have no clue as to the software processes that Fiery runs to create and transmit the rip to the printer, or how the printer interprets the rip. All I've learned is through trial and error. That being said i found the cause; the program that created the imposition made another job act up and i was able to put the two circumstances together to understand the problem lies with the program not Fiery. To solve it i used a 1 up business card art file and imposed it using CWS. Everything worked.

    As to the processes you mentioned adam1991, thank you, but i still don't understand the software flow of the ripping process, and where the image viewer gets its image from. Perhaps that is beyond my understanding, but it would be nice to know in general terms at least.

    Thank you
    dan

  4. #4
    adam1991 is offline Fiery Forum Expert Contributor adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful
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    Image Viewer is the actual pixels that the Fiery creates, the actual pixels that it sends to the print engine.

    Look at the Fiery color flow document. Image Viewer shows the pixels right before calibration is applied.

    Calibration and the engine are, therefore, the wildcards--and I've absolutely seen both of those be corrupt. You can have a good Image Viewer image but a horrible print.

  5. #5
    StarDigital is offline Fiery Forum Expert Contributor StarDigital is on a distinguished path
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    Thank you for that clearup. So let me summarize the process as i see it

    1 PDF is analyzed for CMYK/RGB/Spot values and adjusts the pre-rip accordingly (Lab?)
    2 Result is then adjusted according to the color profile
    3 Ripped (Raw data)
    4 pixel info is then sent (as needed) to the image viewer
    5 Fiery printer interprets raw data and creates laser codes for each of the drums
    6 Drums then transfer to the belt then to the paper in toner, which gets fused.

    So you're saying that if the data sent to the printer is corrupt printer-wise but not fiery-wise i will see a fine Image but a bad print? And can that happen in a variable in the pdf that Fiery doesn't 'see'?

    dab

  6. #6
    adam1991 is offline Fiery Forum Expert Contributor adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful
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    More or less you have it correct. Just follow the Fiery color flow chart for your version of Fiery, and all should be clear.

    Yes, the inbound PDL (not PDF--it could also be Postscript or VPS or PPML or...) is looked at and each element--RGB, CMYK/L*a*b*, named (spot) colors, and black--is run through a separate processing channel inside the Fiery. RGB and CMYK get processed via their profile settings to L*a*b*, which then gets washed through the output profile to create a valid bitmap for that particular engine. Named colors get run through the spot color processing path according to the color flow document and the job ticket settings; if the spot color processing path is used, the name determines the specific L*a*b* value that's picked from the lookup table and then washed through the output profile.

    It's this bitmap that you see in ImageViewer.

    At print time this bitmap is then sent through the calibration curve to the engine, which processes the file its own way and applies its own screening and generates the proper commands for the imaging engine. It's this set of items that I've seen go bad and create a bad print.

    Fixing a corrupt calibration is easy. Worst case reset the calibration then re-do it. The engine is a different matter; in the odd circumstance that it goes bad, it needs service. But good luck getting your service rep to understand what's going on.

  7. #7
    StarDigital is offline Fiery Forum Expert Contributor StarDigital is on a distinguished path
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    perfect! Thank you.

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