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Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

  • 1.  Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 23 days ago
      |   view attached
    I'm a content creator tasked with establishing color profile settings for my employer, as relates to all Adobe CC apps. We regularly provide print-ready PDF to a variety of print providers, including offset, flexo, and digital hybrid.
    I've chosen Adobe RGB for our created print-ready RGB images, and selected GRACoL2013-C1 (CGATS21-2 CRPC6) for CMYK.
    My question has to do with the setting for grayscale.
    The various standard profiles (for example North America General Purpose 2) provided indicate Black default as 20% Dot Gain, and the same for Spot colors.
    Wouldn't I want to set my Black profile to match the cmyk profile (in this case it would display as "Black Ink - CGATS21_CRPC6.idd in Photoshop Color Settings) so that this color behaves the same throughout the remainder of the production process?  [See attached screen cap for these settings]
    In other words, if the black channel in a cmyk image is 50% tint (which passes through into my PDF) wouldn't I want my 50% gray tinted graphic to carry the same profile?
    I can understand spot colors playing by the 20% dot gain rule, as those colors could be controlled on press independent of the cmyk. But the black channel is ultimately shared by both cmyk and grayscale images, and when we have cmyk images we are also likely to have gray images in the document, too. Shouldn't their profile settings match?
    I'm fully open the idea that I'm thinking too hard about this, but I do want to get it right and not just by flipping a coin for each setting.
    Thank you for your input -- it is valued and appreciated. ​​

    ------------------------------
    Brett Stone
    Owner
    Yfficient Graphic Design and Marketing
    Saint Charles MO
    ------------------------------


  • 2.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 23 days ago
    Brett,

    You are 100% correct.

    Don

    Don Hutcheson
    don@...
    908-500-0341
    (Typos courtesy of iPhone's teeny-tiny keyboard and not-so tiny thumbs)




  • 3.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 22 days ago
      |   view attached
    You're 100% correct as Don points you but.... you can forget about it. If you look internally to "Black Ink - CGATS21_CRPC6.icc" and to "Dot Gain 20%.icc" you'll see both are "identical" profiles (except by a little difference I'll mention later on). You can compare them just in PhotoShop (loading them in Gray ColorSpace and then looking to the curve going to custom) or in a match easy way just opening both profiles in ColorSync utility (in a Mac) or with ICC Profile Inspector in a PC. You'll see the KTRC curve (this is a GrayScale profile so it doesn't contain A2B or B2A tables, only curves) is the same one. Ok, you'll note it's starting in a different point (DG 20% starts in x,y 0,0 while Black Ink from CGATS21 starts in x,y 0,2.4) but this is because also the White Point in both profiles is set in a different way and even more this will be only considered if you use Absolute Colorimetric RI.

    So basically if you convert from CMYK to both grayscale profiles of from this 2 grayscale profiles to RGB or other profile, you'll get exactly the same numbers except in the very highlights (below 5%) just because decimal conversions.

    You're assuming "Black Ink - CGATS21_CRPC6.icc" came from the Black channel of CGATS21_CRPC6.icc what it's essentially not true. "Black Ink - CGATS21_CRPC6.icc" is just a synthetic ICC profile (not based on measurements) with a 20% dot gain and a different white points regarding the Adobe one.

    Best regards.

    ------------------------------
    Juan Martorell Climent
    ColorInLab Color Consulting S.L.
    Villarreal Spain
    +34 964 523 278
    ------------------------------



  • 4.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 22 days ago
    Brett,
    I hate to disagree with Juan, but there is in fact a considerable difference between converting to Dot Gain 20% and Black Ink CRPC6.

    Juan, I'm surprised that a man of your intelligence, wisdom, good looks, charm (etc.) would make such a mistake! :-)
    When you select an actual ICC profile as the Gray working space, Photoshop uses its "forward tag" (A2B) data to construct a 1-D LUT that converts from 0-100% K to L*. This becomes the forward tag of the Gray profile.
    Photoshop then inverts that table to create the "reverse tag".
    Note that this is NOT the same as just using the black channel of the profile as an output conversion, because obviously, the resulting tone shape would then be influenced by profiling software settings used when making the original profile, like Black start, Max black, Black shape, etc.

    You can clearly see the difference as follows:

    1. Convert a copy of my "Lab_ramp.tif" image (www.hutchcolor.com/Images_and_targets.html) into Dot Gain 20%, Relative, BPC.
    2. Convert another copy into "Black Ink CRPC6", Relative BPC.
    3. In the Layers window of one of the resulting K-only images highlight the Background layer and shift-drag it onto the other image. The shift key should make them register perfectly.
    4. With the eye-dropper, create locked measuring points on patches that produced 100, 75, 50, 25 and 0% K.
    5. Alternately reveal and hide the top layer (by clicking its eyeball icon) and watch as the percentages change.

    You will see that the intermediate percentages (75, 50, 25, etc.) are significantly different, and shadow detail is also quite different.

    This is one of Photoshop's hidden gems, that allows a 1-channel, black-only, reproduction to almost exactly match the tonality of a CMYK reproduction made for the same device. The only difference should be in deep shadows, which will usually have more contrast with four inks than just black.

    Don


    ------------------------------
    Don Hutcheson
    HutchColor, LLC
    Washington NJ
    908-500-0341
    don@...
    ------------------------------



  • 5.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 22 days ago
    Hi Don.

    This becomes an interesting issue :))

    I'm trying to see and get this differences you mention, but honestly I'm not able to see them....

    I believe the issue is in your PhotoShop settings. Let me proof you.

    Instead of following your steps, do the process as I'll describe it right now.

    1) Open the Lab_ramp.tif.
    2) Add some color sampler tools into it, so you'll have point values.
    3) Duplicate the image so you'll have two Lab images with color samplers in exactly same locations.
    4) Convert the first one to Black Ink - CGATS21_CRPC6.icc" (Relative BPC as your suggestion).
    5) Convert the second one to "Dot Gain 20%.icc" with the same settings (Relative BPC as your suggestion).
    6) As you'll be now on Grayscale in both images, Photoshop rounds values in 8 bits to %, so for getting away of rounding issues, lets convert both images in RGB (AdobeRGB for example), so you'll get really round numbers and not an interpolated %.
    7) take a look to the values and tell me if you found any difference between them. :))) (maybe you'll found differenced by 1 just because the calculations).

    Now arrives a possible explanation of why you're getting this differences if you do the process following your steps. When you "copy" one of the images into the other one (point 3 of your process), by dragging one layer from one image into the other, depending on your color settings, the values of the channel will be converted or not, from one profile to the other one...

    However this will have no sense for me knowing your deep knowledge about this topics, so maybe I'll be missing something. Any idea of why I'm not getting differences if I follow the previously steps? (or even following your steps and ensuring correct color setting in PhotoSop).

    Best regards.






    ------------------------------
    Juan Martorell Climent
    ColorInLab Color Consulting S.L.
    Villarreal Spain
    +34 964 523 278
    ------------------------------



  • 6.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 22 days ago
    Hi Juan,

    As you correctly assumed, when I dragged one image onto the other, I did NOT convert, so the K percentages were preserved.  The appearance of both layers was therefore controlled by the assigned profile of the receiving image.

    Here is the difference I saw after converting into 20% Dot Gain (lower had) and Black Ink CRPC6 (top half).
    I layered the 20% Dot Gain file over the Black Ink CRPC6 file and made a mask to show the difference at the dividing line. The difference is most visible in shadows.



    Your suggested experiment:
    Regarding your suggestion of converting both files to Adobe RGB, of course it seems to show no difference, because the test is fundamentally flawed.  (It's also unnecessary, BTW.)

    Why it's flawed:
    Converting the two K-only files to AdobeRGB (or any destination space) should ideally result in virtually identical appearance, because in both cases, the assigned profile should (hopefully) allow a colorimetrically-accurate translation back to the original Lab condition, as it existed prior to each file's conversion.
    However what we want to know in this case is how would the K-only percentages appear when printed on a common destination device. Those differences are irretrievably lost when you convert into a second color space.

    Why it's unnecessary:
    You can see fractional percentages values simply by changing the eyedropper mode in the Info palette from 8 bit to 32 bit. The numbers are now expressed from 0.000 to 1.000, with three digits of precision.  Here's what it looks like...

    The only slight annoyance is that now everything is inverted (100% = 0.000, 0% =1.000, but at least you have ten times the precision.

    Does this help?

    Don

    **************************
    Don Hutcheson
    President
    HutchColor, LLC
    908-500-0341
    **************************











  • 7.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 22 days ago
    Don and Juan,
    I'm enjoying this conversation on my behalf, and I want you to both know that your input is greatly appreciated. Please stay friends!
    From the demo that Don just posted, I'm seeing that the blacks remain blacker (is that a thing?!) and the tonal range more complete. As a designer, I've often wondered why it was so difficult to achieve a deep black in gray images, and the DG20 may be a contributing factor (We also set our max % to 95%, which may be an unnecessary printer recommendation holdover from 'the old days', and the topic of a different conversation -- I've always wondered why I wouldn't provide the file with full tonal range and the printer adjust for press and paper realities in their process.)
    I welcome additional conversation, whether it's Don, or Juan, or anyone else who would like to chime in. I'm learning much simply from everyone's input.

    ------------------------------
    Brett Stone
    Owner
    Yfficient Graphic Design and Marketing
    Saint Charles MO
    ------------------------------



  • 8.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 22 days ago
    Hi Don.

    Now I see what you're talking about. I didn't realize of it as I was setting all color samples in the mid tones & highlights, and in this areas you can't see differences in color values. Now I've check initial Lab 5,0,0 and it's finishing in 98% in "Black Ink - CGATS21_CRPC6.icc" and in 95% in "Dot Gain 20%.icc", so 3% in difference in this dark areas.... yes, it's mathematically different... but I'm not sure if it'll be visible in a print.

    On the other hand, you're absolutely right regarding the Adobe RGB conversion, I don't know in what I was thinking when I wrote it...maybe Jetlag...

    What I initially was trying to explain Brett was the "Black Ink - CGATS21_CRPC6.icc" is not an ICC created from the black measurements of CGATS21_CRPC6.icc. If you convert the same Lab 5,0,0 into "CGATS21_CRPC6.icc", you can check the black channel finish in 91%. Of course you've the gray area coming from CMY that will increase the amount of gray in this area... but if you extract the just the black measurements from the CGATS of CGATS21_CRPC6.txt and build an output ICC (and convert this ICC from 1CLR to GRAY of course), so if you build a true ICC from the measurements, you can check it's absolutely different from "Black Ink - CGATS21_CRPC6.icc" as "Black Ink - CGATS21_CRPC6.icc" is a synthetic profile, not a profile from measurements as CGATS21_CRPC6.icc". In fact if you do it you'll see this Lab 5,0,0 is finishing on K=100%.

    Brett. Don & me are and will be forever good friends, but both of us loves color and are passionated about it, so if there is something about what to get deep into, both loves to do it even just for fun... :)) Today I was recovering myself from a long trip and I had time for reading this forum.... so I was just enjoying a little discussing about something I like.

    Best regards.


    ------------------------------
    Juan Martorell Climent
    ColorInLab Color Consulting S.L.
    Villarreal Spain
    +34 964 523 278
    ------------------------------



  • 9.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 21 days ago
    I'm still reeling from the shock from reading that content creator actually understands and cares about this detail. Hat's off to Brett, I say. Surely a sound CM workflow begins with thoughtful selection of working spaces and CM policies. The % dot gain settings for the gray space are certainly archaic at this point and should be replaced with the "gray" adopted from the CMYK working space. Perhaps one day Adobe will put this in the update for North American Prepress and the like. Thanks also to Don for illustrating the consequences of deferring to the default gray. The discussion of the spot color working space is far more fraught, unfortunately.

    ------------------------------
    Mike Strickler
    MSP Graphic Services
    ------------------------------



  • 10.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 20 days ago
    Thank you Mike for the kind words.
    Understanding how color management works is such a huge challenge, I can understand why 99.9% of creators seem to not even try, and it would seem reasonable to me for any commercial printer to second guess (or maybe ignore?) what their client provides knowing that it's suspect, at best, under most circumstances. I'm geeky, so I don't mind; many others aren't and just stick with 'this is how we do it.'
    Just today I saw a discussion amongst InDesign users regarding when/if to convert from rgb to cmyk. There was the usual mix of just use the default, to just convert at PDF with preserve color, to the most dangerous convert at PDF to preserve color AND don't include the profile. There was no consideration to the value of passing-along profiles, even if the creator doesn't understand them; maybe their printer does, and blindly converting removes a tool that could be used by the printer to create a great piece. It just underscores that there is little understanding in the design/production community.
    On the flip side, having worked with many commercial printers in book publishing, marketing materials, and direct mail that the printing companies often do a poor job communicating their needs. Maybe they just gave up (I wouldn't blame them), but maybe they just don't understand it all, either, and we just all get lucky, or we work it out on press, or we just don't know what opportunity we're really missing.
    Even with a G7-certified commercial printer we work with frequently has a difficult time sharing how they'd like for us to handle profiles, output intents, etc. They have the internal resources and know-how to be certified, but the communication with the client is difficult.
    I truly appreciate the input from everyone on this matter -- there is still much I must learn, and I also have to explain and defend my rationale. When it all blows up I know the fingers will quickly turn toward me. Another day in paradise (I'll be ok -- work with great people!)
    If anyone from Idealliance is listening, I'm wondering if a valuable training or forum might be built to bridge the communication between creators and commercial printers. Just an idea I know I'd find valuable.

    ------------------------------
    Brett Stone
    Owner
    Yfficient Graphic Design and Marketing
    Saint Charles MO
    ------------------------------



  • 11.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 20 days ago

    Hi Brett,

     

    We're glad to hear this discussion has been productive for you. There is always great discussion within the global G7 communities.

     

    Idealliance's BrandQ® program serves brands, buyers, and creatives to align the entire printing and packaging supply chain. BrandQ is a unique program focused on the packaging supply chain, providing tools, measurements, methods, and language for facilitating effective communications between brands and suppliers. BrandQ helps brand managers, creatives, print buyers, and other members of the print and packaging supply chain communicate expectations and requirements and then carefully monitor and measure these throughout their supply chain as part of our BrandQ Manager certification & training program. Brand managers who take the BrandQ Manager training learn the language of quality control and print measurement and how to effectively communicate expectations with suppliers. They learn how to determine if suppliers can meet their expectations and the how to best work with spot colors, among many other critical components. The program results in a vastly improved brand/supplier relationship.

    More information on BrandQ Manager online training is available here at the BrandQ microsite – www.idealliance.org/brandq

     

    We again appreciate your passion and discussion on aligning with your entire print supply chain.

     

    Please also feel free to contact me directly if you have any questions as well.

     

    Thank you!

     

    Jordan Gorski

    Vice President of Global Certification Programs
    Idealliance
    1800 Diagonal Road, Suite 320

    Alexandria, VA 22314-2862

    Direct: 703.837.1096

    Email: jgorski@...

    www.idealliance.org

     

    Australasia • Greater Bay Area China • Europe • Latin America • Mexico • Pakistan •
    Africa • South Asia MENA • Southeast Asia & Korea • Taiwan

     

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  • 12.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 19 days ago

    Brett,

    Great comments and this was a great discussion. I see the same things you are seeing. Designers/Agencies with no understanding about color or color managements settings and other printers that we work with that are still running density/visual and as you stated "getting lucky" or fixing it on press. Education is the key, especially on the designer/agency end. Its one of our target projects for next year. What I have found is that apart from a few designer with just enough knowledge to be dangerous, most designers want to do the right thing and just need to be shown and educated. Lots of great opportunities out there. Thanks for being one of the good ones, Brett.

     

     

    Mike Todryk | Color Technical Specialist

    IWCO Direct | iwco.com

    O: 952-470-5659 | C: 952-797-3940

    idealliance_certificatebadge_G7expert_80x80_web idealliance_certbadge_G7mastercolorspace_qf_80x80web idealliance_seal_cmp_80x80_web

     

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  • 13.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 20 days ago

    Sidenote:

    I knew this forum was 'my people' when all responses were thoughtful, explanatory, helpful, and kind. It takes time and energy to do that, and it's appreciated.
    Other forums I might have received 37 variations of 'What's a profile?" "I don't see that black option in my InDesign settings," "Color profiles are for stupid people!" and "It doesn't work because of the republicats."
    I may just repost in one just to see!



    ------------------------------
    Brett Stone
    Owner
    Yfficient Graphic Design and Marketing
    Saint Charles MO
    ------------------------------



  • 14.  RE: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

    Posted 19 days ago
    As someone who is on the print end of things and knows a bit about color management, I too have a difficult time "talking shop" with clients and even to some of our in-house staff.
    Besides the Color Management Professional classes provided by Idealliance, does anyone know of any resources that A) will help me better communicate the importance & requirements of proper color management with others and/or B) increase my knowledge of CM and the inner workings of profiles in general?

    Thanks!

    ------------------------------
    Brian Tickenoff
    Art Dept. Supervisor
    Coyle Reproductions Inc.
    Brea CA
    (866) 269-5373
    ------------------------------