RGB black is nice, deep and... well, black. CMYK's default black is dull and... grey. Why so? Because it uses only one ink, which may look well while you are designing (depending on the options), but when you export the file or, God forbid, print CMYK black, it shows its true grey nature.
Here's what I am talking about:
Represented with digits, it looks like this:
R: 0, G: 0, B: 0. It's simple. You block all light and you are left with the fathomless, ghastly black of the void.
C: 0, M: 0, Y: 0, K: 100. Print simple black ink on a white base and you get meh black.
Truth be told, no black would look super black when printed on a t-shirt with a Direct-To-Garment printer, as illustrated by this RedBubble graphic, but still, rich black would look better than poor black.
So what's the trick, then?
Well, working in CMYK doesn't stop you from having rich black. The default black in the swatch is C: 0, M: 0, Y: 0, K: 100, but all you need to do is change the colour of your shape or path to:
C: 75%, M: 68%, Y: 67%, K: 90%
This is the CMYK equivalent of RGB black. Of course, it means it will use colour ink, as well as black ink, to achieve that deep look, but you shouldn't be cheap on the inks if you are printing a t-shirt. :)
NB! If you are using Adobe Illustrator, the default CMYK black would be displayed as regular, rich black on screen. To avoid confusion, set the on screen option to "Display All Blacks Accurately". This is found in Edit -> Preferences -> Appearance of Black.
NB 2! If you are printing from a .png file, I have noticed that Illustrator doesn't export rich black properly when you use the "export" option to create the .png. You don't get true rich black, but sliightly greyer black.
There's an option "Output All Blacks as Rich Black", but the funny thing is that it only works on default CMYK black, not on all blacks as it claims.
Here is what I mean:
Here is what I mean:
The difference is not that big, but I still prefer my files to use true rich black. The only workaround I found is to save the file as .eps, open it with Photoshop, change the colour space to RGB and save as .png.
It takes a bit of extra time, but at least I can sleep soundly in the knowledge that my black is proper all the way. :D
That's it for now, stay tuned for more graphic design tips.