Does not feel right? RBG to CMYK the process

Question

I make mascot logos and have been asked from time to time to deliver a CMYK version of logo.

By googling around, there are claims that simply just "File -> Document Color Mode -> CMYK Color" is enough.

After that i click on one of the colors, i check the color box and type in the CMYK % values, but when i paste these into web generators i got another color output. My case, i pasted the code for a very dark blue, close to black, and it generated a grey color.

This left me frustrated about why color convertion has to be such a fluctuating thing, that clearly makes very little sense to people working for the web.

So real question. Was my method enough?

Example of that dark blue CMYK: 59, 49, 46, 64 RBG HEX: 0d111d

Does this convertion seem right? It's supposed to be printed for a jersey.

Answer 1

Conversions between RGB and CMYK are lossy. They typically can not be reversed perfectly. Part of the reason for this is that the black plate (“K”) is a guess, based on several factors.

If you have an RGB colour that you’re using on the web (which means you’re likely using the sRGB colour space), and you’d like to find the closest match for printed materials, the best option is to find a Pantone colour you like.

Emitted light is quite different to reflected light, so choosing a colour from a Pantone book that you feel matches is the best way. There’s a few reasons for this:

• You can use a Pantone booklet to choose the colour, which means you’re viewing the colour as a printed sample when you choose it.
• You can use the Pantone colour to specify spot colour print jobs. If you’re printing lots of jerseys, there is a good chance the printer will use screen printing and can match a Pantone colour. That’s a safer way to get a good screen print colour than giving CMYK values.
• RGB and CMYK values are largely meaningless on their own. They need to be attached to a colour profile to be given meaning. A HEX value of #ff0000 on the web is really #ff0000 in the sRGB colour space. CMYK values need the same.

If you have access to Photoshop, it can try to guess a Pantone colour based on an RGB value. To do that, open the Photoshop colour picker and choose your RGB colour.

Then, click Color Libraries.

The Pantone colour chosen should be treated as a guess though. You should check against a printed Pantone book, to be sure. Your printer should have a Pantone book handy (they’re fairly expensive, especially if you’re only using them one time).