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Why do greys print Purple

Discussion in 'Roland' started by Hanging_By_A_Grommet, May 23, 2012.

  1. I am trying to print a file that has an award in it that is grey and the test prints keep coming out purple any suggestions?
     

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  2. J Hill Designs

    J Hill Designs Major Contributor

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    custom profile.

    or...

    drop the blues a tad?
     
  3. Jack Knight1979

    Jack Knight1979 Very Active Member

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    I understand this problem. Another thing you can do if the art is vector, is assign a color library gray and it will print PERFECT.

    I just ran some gray posters with a new profile I just built. This particular shade of gray is reddish indoors. Thankfully it's gray in natural light, so I'm fine. I did re-do my color ramps and reprofile it.

    Fine tuning new profiles. yippee.
     
  4. Did you get this sorted?

    Sometimes this can happen with Photoshop files as the grays are a blend of CMYK. If you use Illustrator you can use the preference (edit / Preferences / Appearance of Black) to Output all blacks as Rich Black.

    From my understanding this effects gary in that is uses black only to greate it and the greenish or purpleish hew is removed.
     
  5. Haakon

    Haakon Member

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    Also, do you have regular fluorescent lighting in your work area? These do not output a full colour spectrum, so the light that is reflected off the grey print can get a purple hue. How do they look outside in the sunlight?

    We had the same issues at my old workplace, we got a (then) brand new Mutoh Valuejet 1614 and had to print these posters with a grey background, and they came out grey with a hint of purple when viewed on the worktable. Took them out in the reception area with glass roof/natural lighting and they were perfectly grey.

    First we tried all sorts of profiles, but when we converted the prints to a true greyscale and only black was used from the printer and they still came out purple, we had to look for other sources for the problem. The actual indoor lighting was the problem.

    Solution was to purchase colour-true fluorescent tubes, the same kind as bodyshops/car painters install in the paint booths, but the boss did not want to fork out, so we had to run outside to verify the colours in daylight.
     
  6. bob

    bob Major Contributor

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    When RIPing and printing, grays are just another CMYK value. They are not, repeat not, merely some level of K all by itself. The RIP and/or printer does not recognize a gray tone as such and shut off CMY for that particular tone.

    That being the case, if the unavoidable, and desirable** by the way, CMY values in a particular gray tone are not exactly in balance then that gray will take on a decidedly un-gray hue.

    Grays are difficult. Even the most devout profileistas have just as difficult a time dealing with grays as do mere mortals.

    **The addition of balanced CMY values to a gray tone provides a depth and warmth or coolness unachievable with K alone. Something known to duotone and tritone practioners for eons.
     
  7. P Wagner

    P Wagner Very Active Member

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    It is a rare case where I will (mostly) agree with Bob, but he is largely accurate in this post. Grays that appear neutral under various lighting conditions is one of the most difficult things to accomplish in process printing.

    A properly color-managed workflow will account for gray neutrality, and would resolve this issue, but it takes a lot of work (and knowledge) to get to that point.
     
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