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CMYK - black and white?

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  • CMYK - black and white?

    Hello, i have a black and white picture in sRGB which i will get printed in CMYK, with black ink on white vinyl, is there any risk for any colour changes with only black and white?

  • #2
    You need to ask your printer this question.
    When printing on vinyl, The machines use some sort of a CMYK mix to get any kind of rich black (otherwise the K black looks sort of washed out and gray by itself, with no depth of field.)

    With grayscale imagery printed in 4-color black, you always risk the chance the gray will shift slightly toward cyan or magenta.

    There are various ways to convert an sRGB image to grayscale. One is to simply click Mode>Grayscale and dump all the color data (remember to save this as a copy, you never get that color data back.) With images converted to grayscale in this way, some vendors, not all, will ask for the additional step of doing Edit > Assign profile > Don't color manage. The dot gain for digital printing on vinyl is very very small so you don't need the default 20%.

    The other, better way is to use Image > Adjustments > Black & White.
    Then go to Edit > Convert to Profile and select the proper CMYK profile.
    Again, save this result as a copy as your color data is gone.

    And still, after all that, you may get a shift, so a note to the vendor to make sure the gray imagery is balanced, and getting a proof, is always in order.

    If you are getting a screened print on vinyl in one color ink, you are in fact not doing CMYK, you are doing spot printing and will need to talk to the vendor on how to convert your image to a proper one-color halftone with the appropriate line screen for their silk or web printer. Or usually a better option is have them do it for you for the additional charge.

    Comment


    • HotButton
      HotButton commented
      Editing a comment
      Hah EC. Idiot or not, the printer will appreciate your interest in doing it right. Only stupid people let their ego get in the way of learning things. Anyone doing client work without consulting the output provider, ideally even before design begins, is essentially committing malpractice.

    • salsa
      salsa commented
      Editing a comment
      Ditto what HotButton says! I've had printers more than once thank me for asking questions, they get a lot of people who I think they wish would ask more.

    • EC
      EC commented
      Editing a comment
      Thanks guys! Yeah, I would rather be safe than sorry! This is why communities like this are great -- you get to see things from different perspectives.

  • #3
    Four-color process will give you a richer-looking print than the flat and sometimes lifeless look of a B&W halftone. As pointed out, though, even the slightest variation in ink densities will noticeably shift the end result to warm, cold or yellowish. There have been occasions when I've purposely pushed the color toward a sepia tone appearance just to make it look intentional instead of risking a color shift that I didn't like.
    Last edited by B; 04-30-2017, 11:57 AM.

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    • #4
      I'm on photoshop right now and going to save my image to cmyk, which cmyk-profile should i use as a generic profile for black colour? The site i will order from is based in US/Hongkong.

      Comment


      • #5
        The place you are using doesn't have a posted online spec sheet with that information?
        Or they don't have a download space for job options?

        In the US you would use (most times) U.S. Web Coated (SWOP) v2. There are exceptions to that rule.


        BUT

        No idea what your liason with Hong Kong will do to it.
        Every wide format place has its own quirks. With printing on vinyl, like a bumper sticker, you will run into the concept of ink limits. The CMYK build for black can be very different depending on the media being printed. With SAV (self-adhesive vinyl,) a total ink limit of 200 to maybe 250 is pretty common, otherwise the adhesive is affected by the off-gassing solvents in the ink. This is not stuff the designer generally needs to worry about other than being aware of it, and asking when it comes to Rich Black builds on various wide media.

        And you still run the risk your grayscale will tip green or pink. Get a proof.


        I don't offshore much. When I do it is spot color Pantone and I don't expect magical results.
        Last edited by PrintDriver; 05-02-2017, 07:09 AM.

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