CMYK to RGB

[JagInTheBox]

Hey guys,

yes i know something similar has been asked before but all the other posts I have seen didn't answer my question. 

I understand that converting RGB to CMYK withhout color differences won't always be possible since the color garmut of RGB is a lot bigger than the one for CMYK.
What I don't understand is: If i try to do it the other way (CMYK to RGB) shouldn't it be possible to get the same color in RGB as I have in CMYK?

Maybe you can also tell me how you handle it if your client needs a logo in RGB and in CMYK colors and wants them to be similar.
 

Thanks a lot in advance can't wait to hear your replies.

 

Greetings,
Julian

Icon_Farbe.pdf

Icon_Farbe.pdf

[Czokalapik]

Google "cmyk rgb gamuts", there is no 100% coverage in cmyk and rgb gamuts, in either way. You can have bright red color in RGB, but can't print that bright color in CMYK, but you can have dark yellow/greenish in CMYK, but can't display such color on your monitor in RGB. Plus never assign profiles, always convert your files to profiles.

 

In general, when I'm designing logo or something important like that, I'm trying to use colors that will display in similar way on screen as when I'm printing them. I don't own Affinity (yet :D) but PS have small boxes next to color wheel, those boxes will show colors you are choosing, sometimes with exclamation mark sign, this indicates you won't be able to print this color (not in CMYK gamut). I'm sure Affinity have same basic functionality, so use that.

 

As for clients who can't understand the fact that monitors use different "colors" than print and are stubborn about it I have simple solution: Once I did designed some random graphic with specific colors. I chose those colors to show that not only printed colors will be different on professional and home printer, but also they will be different on different screens! Usually explaining the fact that every screen have differend spec, different ICC profile, different material will not only enlighten ppl about cmyk/rgb difference, but they will also realize that color will be different in different environment, on different screens etc.

[JagInTheBox]

Thank you guys! I appreciate both answers A LOT! They helped me explain the topic to my client so he understands where I'm coming from.

@Czokalapik

22 minutes ago, Czokalapik said:

Plus never assign profiles, always convert your files to profiles.

I am not 100% what you mean by that. I know you can set/assign a specific document to a specific ICC profile which alters the color output on the display (print shop wants ISO Coated V2). But I never heard about "converting files to profiles" is that only possible in Ilustrator or in Affinity as well?

[Czokalapik]

This is the best way to describe it found on Adobe forums (again, I'm not yet happy owner of Affinity, waiting for Indesign alternative to buy all 3 programs): Converting changes the pixels’ RGB-values to maintain the color impression while assigning leaves the numeric values unchanged but uses a different profile which can cause the appearance to change significantly.

 

Like in PS you can press ctrl+Y on rgb document to "see it in cmyk", but for more complex files there will be difference between this and converting it to CMYK (and it depends on actual profile you'll use). and if you are changing between rgb-rgb profiles (or cmyk-cmyk), you can assign profile OR convert it.

ps, if you are not working on image for later hq print (mainly web image and/or something that has to be as similar as it get everywhere, like  logo), use sRGB because it has way smaller color spectrum than adobeRGB etc. and it can/will be displayed on every screen (only specific monitors created for graphic designers/ dtp specialists can display Adobe RGB, not to mention prophoto rgb, that has wider color spectrum than you can see).

[JagInTheBox]

@Czokalapik
So what you're saying is I should work in RGB until Exporting it. Then with the Export Persona (see Example Export.jpg) I would select PDF CMYK and ISO Coated V2, correct?

@BofG
Thank you for your explanation. I just tried what Czokalapik told me and it the result is the same with "Convert" in the Document Settings as with changing it at the end during exporting. Now if I change the RGB profile to a CMYK profile it doesn't give me the choice between assign and convert since they're both greyed out/inactive. Can you explain to me why it doesn't give me the option if I change from RGB to CMYK. It only offers those buttons with an RGB to RGB change.

[Czokalapik]

@JagInTheBox 

What I'm doing depends on the project.

• Working on photo from professional camera: Adobe RGB all the way since I have monitor that can display 99% of it's colors. Convering it to CMYK will destroy part of image's color. Save as Adobe RGB too.
• Working on project for print: set up to CMYK file (in my country most popular profile is FOGRA39) and import all the images, export without any profile or with desired CMYK profile (depends what printing company want).
• Working on web images or things that have to be similar across all media: sRGB and export with profile included (exporting image without profile will result in different color on screen between image and html color even if it's same exact rbg color). For things like logo I'm usually starting with rgb, checking how it will look using CMYK, if client will like it I'm choosing pantone colors, making print proofs, if something is off (between cmyk/pantone), I'm changing pantone, if I can't find good match, change cmyk to match pantone and then adjust sRGB. (PS. while choosing pantone/cmyk match, make sure you have good lightning, sunny day without direct sunlight is perfect for me, you can use something like D50 Lighting Indicator Stickers as really cheap lightning indicator. While matching rgb-cmyk both lightning and monitor profile are important, on good monitors profiling should usually be done once, I'm using i1Display Pro once a year or so, but nothing changed since my first setting).

I'm not using ProPhoto RGB since Adobe RGB offers best match between what I can see, what my monitor can display and what will be printed.

[Thomas Cobb]

1 hour ago, Czokalapik said:

As for clients who can't understand the fact that monitors use different "colors" than print and are stubborn about it I have simple solution: Once I did designed some random graphic with specific colors. I chose those colors to show that not only printed colors will be different on professional and home printer, but also they will be different on different screens! Usually explaining the fact that every screen have differend spec, different ICC profile, different material will not only enlighten ppl about cmyk/rgb difference, but they will also realize that color will be different in different environment, on different screens etc.

That's genius! I will borrow the trick from you, if you don't mind. Do you show your graphics on several monitors to explain?

[Czokalapik]

@Thomas Cobb

Yes, that's the trick. Showing it on 2 phones and PC/laptop, plus the best trick is (since I have 2 same phones) is to set screen brightness to half on one, and to max on the other one. That should do the trick even with hardest clients  My friend showed me that when he was working in printing company, although he was using printed cmyk color + pantone swatch - he was asking client to select best matching pantone, then he was taking him to another room with good lightning and clients had to select best match again - it was almost always different choice! Nothing can teach better than own experience.

[JagInTheBox]

@Czokalapik  I did it the same way you said you do it and my client finally accepted the small color difference between print and screen after comparing different company screen logos with the print version. So thank you for that tip!

And thanks to everyone else who helped me solve this problem and got me to understand the difference between CMYK and RGB and why you can't make them look exactly similar.

I have to say this has been by far the best experience I made regarding being part of an online forum!

[Czokalapik]

@JagInTheBox I'm happy happy to hear that

Btw, just downloaded trial of Affinity Photo and it is amazing, you can open your file in Adobe RGB (or create one) and add 2 layers of adjusments: Soft proof with sRGB and Soft proof with desired CMYK profile. You can mask those layers half-to-half to see how your logo (or any other project would look like both in print AND on monitor!

I don't think you can have 2 soft proof previews at once in PS, AMAZING!

Edit: ofc you still need to profile your monitor, print with proof and there is still a matter of different displays on different devices.

Edited April 18, 2018 by Czokalapik

[ashokcool2636]

double cyan = 35.0/100.0;
double magenta = 29.0/100.0;
double yellow = 0.0;
double black = 16.0/100.0;
you can easily perform CMYK to RGB conversion,First You divide every value by 100 since it need to come in the range of 0 to 1 then
        R=255*(1-cyan)*(1-black);
        G=255*(1-magneta)*(1-black);
        B=255*(1-yellow)*(1-black);
In this way we will get almost approximate values

Edited March 7, 2019 by ashokcool2636