1

EDit: The Image is in RGB mode and it needs to be saved as an PNG!

I need to change the CMYK values of a logo to C:16%, M:100%, Y:79%, K:5%.

ColorPickerBefore

But after I confirm these values, no matter what method I use to change the color, I get these values: C:17%, M:99%, Y:79%, K:5%.

ColorPickerAfter

The Hex stays consistent at #be0438.

Can I somehow force the CMYK to not change (my client won't accept the work if it's not the correct CMYK)?

  • 1
    It can not be cmyk if its a png. – joojaa Aug 9 '18 at 11:05
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You can NOT. There is no workaround, there is no shortcut, there is not an alternative way.

  • If the file is in RGB mode it is in RGB mode.

  • PNG does NOT accept CMYK mode.


  • You SHOULD change the color mode to CMYK, adjust the color and use a file format that accepts CMYK. Your options are TIF or PSD itself.

  • The CMYK value needs to include the color profiles used. Normally this would be "Adobe 1998" and one specific where you live, for example, SWOP, Fogra, Japan, etc.


It has no sense that the client asks a CMYK PNG, it does not matter if it is for a webpage. That is NOT how things work.

When you are reading a CMYK value from the color dropper on Photoshop you are NOT reading any CMYK value. The program is "inventing" those values on the fly in the case you want to actually convert it to CMYK and save it in a file format that supports it.


Edited to clarify @Danielillo's comment.

I need to assume somethings.

  1. You want PNG format probably because you know it is a lossless format for a webpage. On a web page, you need an RGB image.

  2. But in this case, the client feels insecure about using another color that another designer (wrongly) defined as CMYK, just because that is what the company's image design guidelines states.

A color conversion is done on a matrix of ranges. On an RGB file, you have potentially 16 million combinations of values to get potentially 16 million different colors.

But if you add another channel you have potentially 16 million x 256 or 4 billion combinations of colors...

But there are several issues here.

a) You can not get 4 billion colors from a 16 million source. You convert values from ranges.

b) On a CMYK print, you have even less color gamut than an RGB file so you actually have less than 16 million colors.

c) On CMYK file, regardless you are actually using 256 levels on each channel you are rounding the values from 0 to 100%. This is, the color combinations of the matrix use a maximum of 100 ^ 4 or 100x100x100x100 possible combinations, that again exceeds the real gamut of the color mode.


d) A color has different ways to be interpreted on a print. It is not very common but the two ways are a "chromatic combination" or an "achromatic" one.

A color can be defined as a combination of CMY+K inks or a combination of K+CMY ones... Yes I know that sounds silly.

This means when a color gets neutralized by a combination of C+M+Y values, this color can be replaced by a K ink.

e) A color profile does not shoot black ink on light colors, for example, to avoid the user seeing black dots.


All these elements give you "gaps or steps" on the color conversion.

On @Danielillos tests he assigned Y:80% but this value jumped to Y:79% again because the RGB value was reinterpreted as that value.

  • If is not possible at all, I wonder how I could. There must be a way to recreate and keep this fake CMYK value in a RGB file to save a .png RGB and make the client happy. By the way, this is another subject, clients are clients and we can tell them what they need and what they don't but some of them will accepted and many others no :-) – Danielillo Aug 9 '18 at 11:09
  • There are two points here. No, a client does not know what they need. If you go to the medic you do not ask them to give you X medicine on Y format or else. It is the professional obligation to guide the client to what he actually needs with the best available options. For the first part, I will expand a bit on the answer. :o) – Rafael Aug 9 '18 at 11:19
  • I agree, it's the perfect theory, but reality has many colors. If the theory is perfect, supposing that its implementation is also perfect means utopia. – Danielillo Aug 9 '18 at 11:37
  • @Danielillo CMYK to RGB is a many to one conversion so many different cmyk values can map to same RGB value. Therefore you can not rely on a color to turn back to said cmyk value when converted back. What color it is out of your control. Even if you can get the same cmyk value in PS, there is no guarantee that another application will do that or even that a differently configured PS will. Since PNG can not be guaranteed to carry the setting you can not rely on this to get paid if the condition of payment is tgis cmyk or no money. Use a CMYK format. – joojaa Aug 9 '18 at 13:21
-1

Assign a RGB profile to your document and do not change the profile when creating the .png.

To match the exact color I defined C:16%, M:100%, Y:80%, K:5% and after editing it I've got C:16%, M:100%, Y:79%, K:5% at the original file and the .png copy.

At the left the original file, at the right the .png.

Color Picker

  • Hey, sorry i just realized i didn't add the most important detail, the image is in RGB and it needs to be saved as a PNG file. In CMYK there is no problem. – user125699 Aug 9 '18 at 8:01
  • Answer updated with the RGB file – Danielillo Aug 9 '18 at 8:13
  • Thank you for your help but on the color profile i'm using, sRGB IEC61966-2.1, changing the Y value doesn't affect the C nor the M value. Do you have a custom profile or which one are you using? – user125699 Aug 9 '18 at 8:27
  • I'm using the same profile, but Photoshop CC and the color keeps the same values. – Danielillo Aug 9 '18 at 8:38

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