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ted939
Known Participant
February 28, 2022
Question

Info Panel color values are what unit of measure?

  • February 28, 2022
  • 4 replies
  • 3751 views

When viewing Info panel color values (whether CMYK, RGB, etc), what do the % values and the non-% values next to them represent?

% of what (for the % values), and # of what (for the non-% values)?

What are those units of measurement? I can't find that info anywhere.

Thanks!

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4 replies

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ted939Author
Known Participant
March 1, 2022

I think I now know the answer to my original questions, as I've distilled/compiled from all the info from this thread and elsewhere.

Would you please confirm if I now understand this accurately, @D Fosse , @TheDigitalDog , @Warren Heaton10841144 , @Test Screen Name , @Semaphoric and @davescm (and anyone else that reads this!)?

 

1.  The RGB #s are not percentages, and they have no unit of measure; they are numbers on a scale of 0-255, where 0 is the darkest of whichever color it refers to, and 255 is the brightest of whichever color it refers to.

  0-0-0 makes total black

  0-128-0 is no Red or Blue, with medium Green

  0-255-0 is max (saturation and brightness) Green

  128-255-128 is max Green, slightly muted with medium Red and Blue.

 

255-255-255 is max Red, Green and Blue, making total white.

 

 

2.

   In this sample taken from a Curves Adjustment Layer, the CMYK number values that do not have a percentage symbol next to them (preceding forward slashes and number values that do have percentage symbols next to them) actually are % values. (64, 51, 50, 75 in this picture)

For example, the "C: 64/ 72%" in the screen capture above, should read "C: 64%/ 72%" (including the "%" after the "64")

***Why not put that ONE extra character in there for clarity, Adobe??***

 

3.  CMYK values (which are all/always percentages, even if no percentage mark next to them) are on a scale from 0%-100%, with 0% being none of that ink being placed, and 100% meaning that whichever printer or press is used will as much as it can at any particular area with whichever ink(s) the 100% refers to.

There is no way to know/see exactly what that "100%" ink amount will look like printed until there is a print of it to look at.

There are color management profiles that can be selected in PS (and more that can be added to PS) that will help by displaying an on-screen approximation of what a 100% ink setting (and all other settings on PS) will look like printed, but it may take trial and error, printing until one becomes familiar with how the image on the screen relates to its print on any given printer.

 

4.  The numbers/values to the left of forward slashes refer to values before an edit, and the numbers/values to the right of forward slashes refer to values after an edit.

 

Conrad_C
Community Expert
Conrad_CCommunity Expert
Community Expert
March 1, 2022
@ted939 wrote:

4.  The numbers/values to the left of forward slashes refer to values before an edit, and the numbers/values to the right of forward slashes refer to values after an edit.

 

Not any edit, but before/after calculating the result of all edits made specifically using adjustment layers in the Layers panel. As shown below, if there are no adjustment layers, there is only one color value per channel, for the one Background layer, no matter how many edits have been done to that layer.

 

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Test Screen Name
Legend
February 28, 2022

For the CMYK values, it's percentage of ink. Like, 100% C is the maximum amount of cyan ink. 50% C is half as much ink as that. And 0% C is no cyan ink at all. If all the CMYK values are 0%, there's no ink at all, just blank paper. 

    T
    ted939Author
    Known Participant
    February 28, 2022

    Thanks for your reply, Test Screen Name!

     

    I understand that 0% is no cyan ink at all, but what do you mean by "the maximum amount of cyan ink"? 

    In reality, as long as humans can continue making cyan ink, there is no "maximum amount of cyan ink" without a qualifier telling the context, so I don't get it.

     

    The maximum amount of cyan ink that the paper can absorb? The maximum amount of cyan ink in the printer's cyan reservoir? I'm sure it's neither of those two, but I don't know what it is.

     

    The maximum amount of cyan ink that _____ ?

     

    Thanks!

    T
    Test Screen Name
    Legend
    February 28, 2022

    The maximum amount of ink that this printer could put at that place. Think of the ink as coming through a tap and it's full on. The amount of actual liquid is going to vary enormously, depending on the equipment. (As an aside, on cheap paper, with a fast moving printing press, 100% of all the inks at the same time is way too wet, and the paper falls apart. Part of the job is making sure that much ink isn't allowed). 

      D Fosse
      Community Expert
      D FosseCommunity Expert
      Community Expert
      February 28, 2022

      And also note that the actual numbers refer to your working spaces. The numbers will vary in different color spaces.

       

      That's why, for instance, 128-128-128 does not necessarily correspond to 50% K! It will only do that if the RGB space has the same tone curve (gamma) as the working gray, which it won't have at default settings.

        T
        ted939Author
        Known Participant
        February 28, 2022

        That's above my head at this point, and not exactly addressing my question, but I appreciate you offering that info, that will hopefully make sense/mean something to me at some point.

         

        Thanks!

        Semaphoric
        Community Expert
        SemaphoricCommunity Expert
        Community Expert
        February 28, 2022

        The percentages are for CMYK and Grayscale, and refer to the ink coverage  — 0% is paper white, 100% is total ink. Halftones are in between.

         

        The non-percentages are on a scale from 0 - 255, the range of 8 bits (even for 16-bit images).

         

          T
          ted939Author
          Known Participant
          February 28, 2022

          Thanks for your reply, Semaphoric!

          Follow-up Qs:

           

          a. When you say "100% is total ink", what does "total ink" mean?

          Like if I said that a drink is total juice, then I'd know nothing else in there, but if only 60% juice, then there might be part juice and part water.

          So, "total ink" as opposed to what: part ink and part  ____?

           

          b. What does % refer to?

          Like if I said someone ran 50% of a marathon, I'd know that the unit of measure is miles, the 100% quantity is 26.2 miles, so 50% would be 13.1 miles.  100% quantity is 26.2, and unit of measure is miles.

            In CMYK or RGB, what is the unit of measure, and what is the 100% quantity in those units?

           

          c. Is that 0-255 range for both CMYK and RGB?

           

          d. Why does RGB show two side-by-side differing non-% values, while CMYK shows a non% value next to a % value.

           

          Thanks!

          TheDigitalDog
          TheDigitalDog
          Inspiring
          March 1, 2022

          Thanks for your reply, thedigitaldog - and nice Spinal Tap reference 🙂

           

          A: 100% of all what ink that is defined by that output? Of all the ink defined by that output in certain amount of printer placing the ink? YES, how do we measure how much ink correlates to a certain % of ink that is defined by that output (color space)?  What is the unit of measure for the quantity of ink to which we apply the %? I'm guessing the unit of measure is a inkVolume, or inkVolume/print time, or a inkVolume/paperArea or something like that.

           

          B: If you don't get what quantity a % applies to, then how can you have any idea what the result will be? If someone asked you if you want to put a certain % of ink on a page (or help perform a certain % of a job, or eat a certain % of a meal), you'd wann know what 100% of it refers to. 100% of a meal is 5 jars of peanut butter and 17 apples, you'd probably decline?  100% of a job is 130 hours in a week? You might decline.  100% of a certain color's ink is a tablespoon per square cm, probably not a good idea. So, it's necessary to know, what #s and %s refer to. Basic math/science concepts like we learned in grade school, right?

           

          C: Yep - I'm very familiar that equal RGB values represent neutral/shades of gray (white to black)

          You say CMYK is always a percentage, but that's not true in my Photoshop Info Panel (see below). You can clearly see 64, 51, 50 and 75.

          What do those refer to? 64 of what of Cyan? And 72% of what? And 34/42 of what for Red?

          And what scales do those fall on? Scale of 0-255 for RGB I did know, but no matter how jet black or stark white I sample in an image, the values never come anywhere close to 255.

           

          D. Why does RGB show two side-by-side differing non-% values, while CMYK shows a non% value next to a % value.

           

          Thanks!


          A: 100% of the ink defined by the CMYK profile. Load/use a different CMYK recipe, you get a different set of values.

          B: Again, the profile is supposed to define the output. It should, but does it? Can't answer that: YMMV.

          C: That number is based upon the RGB values converted to CMYK by the profile again. But what counts is the percentage. Because that's what's "supposed" to be taking place in output but again, will it?

          When you see two sets of numbers like above (R34/42: Before and After an edit.

          Author “Color Management for Photographers" & "Photoshop CC Color Management/pluralsight"
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