JobOptions and ColorManagement

Hi,
I've searched both here and on Lulu xPress, but I've found contrasting information so I'd better ask directly. I've seen at least two different color management behaviors in Lulu provided joboptions (JO) files.

  • The JO that is attached in this post (named lulu.joboptions) has "Leave color unchanged", which is the same of this post – even if the post itself suggests to use CMYK but without specifying which one.
  • The JO that is found in Lulu xPress template (named Lulu-Interior-Print.joboptions and Lulu-Cover-Print.joboptions – two identical files) wants to "Convert all colors to sRGB".

My input is a PDF (that comes from Leanpub), which I'm preflighting against PDF/X-1a standard (flattening transparencies, adding bleeding etc.). I would need to know which CMYK to convert images to.

Thank you for your support,

Davide

Comments

  • Just KevinJust Kevin Lulu Genius
    I just use 'millions of colours' jpgs at a min of 300dpi. That's what bubblejets and laser printers use, and that's what POD normally use. No more printing plates.
  • Hi Kevin,
    thanks for replying. Having worked as a color-management consultant in press/prepress earlier in my career, I wish it was that simple ;-) Quoting one of the posts I've linked above:
    Our printers use CMYK color space for all color printing. We recommend using the CMYK settings when generating your files for color printing. If you use RGB color space, RGB colors will be converted to CMYK colors during the print process. This may result in unexpected changes to color.

    I can assume that sRGB may be chosen so that Lulu can convert to CMYK in-RIP on a machine basis, (e.g. this batch of prints goes to machine X, so RIP will convert to that specific ICC, etc.) but that would be quite limiting on authors' side.

    Given the kind of paper and ink (standard vs. premium) combination, different TAC thresholds may be chosen:

    Solid blacks will print solid at 100% with no other colors added. If you do add colors to improve the richness of the black, TAC (total area coverage) should never exceed 270%.

    No matter the technology, printers still use at the very least CMYK inks, so there is no such a thing as a RGB printer. 

    It would be nice to know from Lulu's tech department whether a CMYK image embedded in the PDF is going to be repurposed to another CMYK profile, left as is (interpreted by the numbers), or converted to a standard RGB and then back to CMYK in-RIP.

    For my few copies, test print run I've just used their template joboptions, but I will not print a larger batch without knowing in advance some detail of Lulu's workflow.

    Regards,

    Davide

  • Just KevinJust Kevin Lulu Genius
    Well, as I say, that sounds like the colour separations as per used for creating a plate for each colour. Bubblejets etc., may use the same colour inks, as you have rightly said, plus black and sometimes Photoblack, but in one pass, even mixing as they go along. I just create jpegs and let the Conversion to 'Print Ready PDF' here sort them out, because that's what happens. That's all that Lulu send to their printers, that PR PDF. As I often say, the proof is in the Proof.
  • Hi David,

    I have created a support case with our print team so that they can follow up with you regarding your questions.
  • Hey Everyone,

    I wanted to follow up on this thread with additional information from our print team regarding CMYK and our Joboptions file.

    When designing your materials, setting your colors to either sRGB or the SWOP v2 CMYK you'd find in Photoshop will likely be fine, but the best test is going to be ordering a proof copy to see how the colors print. Our joboptions files attempt to standardize the files in ways for our various printers, but then our printers are going to make their own conversions to have files work best with their particular materials and machinery. The CMYK that you submit may just be slightly different than the CMYK that ultimately prints, so having that proof copy first off will allow you to then make adjustments to work around those potential differences for subsequent orders.

  • Just KevinJust Kevin Lulu Genius
    Indeed. The proof is always in the Proof  :)
  • Just KevinJust Kevin Lulu Genius
    It is always a good idea to print a test page on your own home printer to see if the colours match what you see on your screen. If not then adjust the screen until they do. That way it is normally WYSIWYG. But that does not always mean the colours on the Proof will match, so follow what Taylor says to adjust them.
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