Skip navigation
Jan Renette
Jan Renette
Currently Being Moderated

"Black" in RGB versus CMYK colors

Mar 5, 2012 9:31 AM

More a question than a discussion.

Just started with ADOBE INDESIGN 5.5 and created a document of 160 pages in 30x30 com format to be printed with Blurb later on. My images are in sRGB (or ADOBE-RGB) where the color "Black" is defined as RGB 0-0-0 (and translated into C91 M79 Y62 K97 in InDesign).

As background for the image in full spread in InDesign, I use the swatch "Black", defined as C0 M0 Y0 K100. However, when I print the document for proof in PDF, the CMYK background is "grey" and the RGB image really black. What is the reason???

 

I went somewhat further in my test to find out the reason...When I open the PDF proof document in Adobe Photoshop 5.1 and I check the colors, the swatch Black C0M0Y0K100 (added InDesign)  has been translated into R34 G34 B33 / C75 M65 Y62 K82.

So I have two blacks, the C91 M79 Y62 K97 (R0 G0 B0) from the placed image,  and

                                     C75 M65 Y62 K82 (R34 G34 B33) from the background Swatch.

 

I changed one of the backgrounds in InDesign into RGB colors (RGB 0-0-0) and then everything is OK on the PDF output. Does this mean that for consistent "Black" in printed book pages, you have always to work either in RGB or in CMYK, not at all in both combination. And is this the same for text defined in CMYK??

 

Thanks for your help.

Jan RENETTE

 

http://j.renette.free.fr

7471 Views   8 Replies   Latest reply: Gernot Hoffmann, Mar 13, 2012 1:12 AM
 
Replies
  • Andrew Rodney
    1,104 posts
    Apr 16, 2009
    Currently Being Moderated
    1. Andrew Rodney,
    Mar 5, 2012 9:36 AM   in reply to Jan Renette
    Report

    Adobe treats process black (which is what you are getting with the CMYK conversion) versus Rich Black (for say type) where the later is always 100% K with zero CMY.

     
    |
    Mark as:
  • Jan Renette
    Currently Being Moderated
    2. Jan Renette,
    Mar 5, 2012 9:47 AM   in reply to Andrew Rodney
    Report

    Thanks Andrew,

     

    Practically, what does this mean for me...????

    Do I have to translate all background BLACKS in INDesign to R0G0B0, or create in Photoshop a "background photo R0G0B0 (Black swatch)", which I place on each page where I need a black background???

     

    Thanks for your help. I am a little lost with black, rich black etc. For me, there is Pure Black and Pure White, with tints between, beeing 256 tints of grey in 8bit..

    Jan

     
    |
    Mark as:
  • Andrew Rodney
    1,104 posts
    Apr 16, 2009
    Currently Being Moderated
    3. Andrew Rodney,
    Mar 5, 2012 3:05 PM   in reply to Jan Renette
    Report

    The question becomes, do you want black to be defined as 100% K only or using the process the profile describes for black? For type, you’d probably want 100% K only and that is what should happen in ID. But for an image, not necessarily the case. You’ll get black assuming the profile correctly defines the CMYK process (for process black).

     
    |
    Mark as:
  • Jan Renette
    Currently Being Moderated
    4. Jan Renette,
    Mar 6, 2012 12:37 AM   in reply to Andrew Rodney
    Report

    Feminite-pages140-141.jpg

    Thanks Andrew,

    Here one of the spreads in the book. At the left side and part of the right page, the sRGB image from Photoshop with black border around as RGB 0/0/0. At the right ( under the text part) background color from InDesign, defined as 100%K. Difficult to see on this reduced image, but the right part is "gray" (in reality (R34 G34 B33), the left border "black", so color difference. I need a consistent background color over the whole spread. That means in my opinion that I have to create a different swatch color black  RGB 0/0/0 for all the backgrounds, and use the 100%K only for the text when having white backgrounds. Do you agree with this???

    Thanks a lot for your help...and hope that it will help also others, because I found a lot of equal questions on the forum. Again, thanks a lot.

    Jan from Toulouse, France

     
    |
    Mark as:
  • Gernot Hoffmann
    Currently Being Moderated
    5. Gernot Hoffmann,
    Mar 6, 2012 1:18 AM   in reply to Jan Renette
    Report

    Jan, you may proceed as follows.

     

    1) Ask the printer, which CMYK profile is most appropriate for his offset process.

    2) Most common in Europe is Iso Coated v2 (ECI).

    3) Choose this profile in Photoshop for CMYK and synchronize all programs by Bridge.

    4) Choose either sRGB or AdobeRGB as RGB-profile, but don't change it later for the

        same document.

    5) Optimize all RGB images and embed always the profile.

    6) Verify by View > Proof Setup (Iso Coated v2 (ECI) > Proof colors / Gamut Warning

       that the RGB image is printable without change of appearance.

       Eventually apply modifications (often a saturation reduction).

    7) Finally convert to CMYK and save as a new version.

    8) Editing in CMYK is a matter for experts. One can easily get too much ink

       (Total Ink Limit violation).

    9) Make the InDesign file. This does not have a global RGB or CMYK mode.

        Both types can coexist (opposed to Illustrator). Just this is the problem.

    10) Create a swatch for Rich Black in ID. That's the darkest printable black.

        Define in Photoshop R0G0B0 or L0a0b0 and read (for Iso Coated):

        C88M79Y64K93. Use these values for the swatch.

    11) Use the Rich Black Swatch for your background, if you like.

    12) Place your CMYK images.

    13) Type text by C0M0Y0K100 = K-only. Overprinting, unless the size is very large.

    14) Export as PDF/X1a. Colors unchanged. No profiles embedded. But Output Intent

       Iso Coated v2 (ECI).

    15) Check by Photoshop. Open as CMYK file (!!). Your Rich Black Swatch and all

       the other swatches in CMYK will have the defined values (the will not, if you open

       the file as RGB file). Verify by values in the Info Panel.

    16) Verify PDF/X1a compatibility by Acrobat Professional > Print Production > Preflight.

     

    There are here and there alternatives.

     

    About Rich Black:

    http://en.wikipedia.org/wiki/Rich_black

     

    Best regards --Gernot Hoffmann

     
    |
    Mark as:
  • p_d_f
    Currently Being Moderated
    6. p_d_f,
    Mar 7, 2012 3:05 PM   in reply to Jan Renette
    Report

    You're printing with Blurb. That's a digital press. You HAVE to specify your background colors as CMYK process - percentages of Cyan, Magenta, Yellow and Black. Then you have to make sure that whatever your black background of your image is in cmyk is and use exactly the same build in Indesign.

     

    It looks like you've got white type, but if you did have black you never want what Andrew calls a "rich" black, because in the inevitable event of plate misregistration, your type would have color fringes from the cyan, magenta and yellow plates. Not pretty. Black type is virtually always spec'd as 100% K for that reason.

     

    But back to your problem. This is the reason you have to design projects like this in CMYK, no matter how many people tell you it can all be done in RGB. It can't, unless you know for sure that your blacks from your different design elements will end up with exactly the same cmyk build percentages. And you'd be surprised at how little deviation it takes to actually see it in print. Enough that you should even turn the dithering off in the convert to profile dialog, as that alone can cause a visible change.

     
    |
    Mark as:
  • Jan Renette
    Currently Being Moderated
    7. Jan Renette,
    Mar 12, 2012 1:17 PM   in reply to Gernot Hoffmann
    Report

    Thanks a lot Gernot,

    I learned a lot of wikipedia..Thanks a lot for this link. It recognized the C91 M79 Y62 K97 (the R0G0B0 in photoshop, translated into CMYK in Adobe Indesign) as Rich Black FOGRA39 coated paper standard)...

    You mentioned "C88M79Y64K93" in your responce..Why this difference?

    I am working on your answer, to practice this and I will keep you informed of the results. Thanks again.

    Jan

    .

     
    |
    Mark as:
  • Gernot Hoffmann
    Currently Being Moderated
    8. Gernot Hoffmann,
    Mar 13, 2012 1:12 AM   in reply to Jan Renette
    Report

    Jan

     

    you're welcome. The percentages of the four inks depend on the profile,

    that's to say on the specific printing process. That's the reason for

    different 'mixtures'.

    Using exactly the same mixture as indicated by Photoshop for a profile

    with input L=0,a=0, b=0 (same result for R=0,G=0,B=0) would deliver a

    background black which matches exactly the darkest black in images

    nearby.

    Using for instance C=70, M=70, Y=0, K=100 would deliver a Rich Black

    as well, e.g. for a page background without special reference to images,

    here with a reduced amount of total ink coverage.

    By the way: adding ink Y can make the appearance lighter instead of

    darker.

    For offset printing we have (or had?) in Europe two standard profiles:

    Isocoated_v2_eci.icc

    Isocoated_v2_300_eci.icc

    These are the official filenames. The first profile has 320% or 330%

    total ink coverage, the second 300%.

     

    Best regards --Gernot Hoffmann

     
    |
    Mark as:
Actions

More Like This

  • Retrieving data ...

Bookmarked By (0)

Answers + Points = Status

  • 10 points awarded for Correct Answers
  • 5 points awarded for Helpful Answers
  • 10,000+ points
  • 1,001-10,000 points
  • 501-1,000 points
  • 5-500 points