Black

Question

I am currently designing a billboard on Illustrator. The background is black on the screen. I used CMYK  0 0 0 100.  But when I save it as pdf or export is as JPG, it becomes greyish in pdf/JPG. Why is that? On the other hand, if I use RGB in Illustrator (and not CMYK) and use RBG 0 0 0, what I get in the pdf or JPG is what I see on the screen, that is black. The colour does not change in thsi case from illustrator (black) to pdf/JPG (grey).
Should I use RGB or CMYK? Is there a way in which I can use CMYK and secure the same colours for my illustrator file and pdf file?  Using RGB solved the problem but do printers accept RGB? RGB seems to secure consistency between pdf, JPG and illustrator but not CMYK.
Thanks for your help!!!

Answer 1

Blacks are more complicated than you would expect. Whether you use RGB or CMYK is dependent on your method of production. If you're having this billboard printed, you would generally use CMYK, unless the printer specifies otherwise.
Here is a chart showing values for different blacks for CMYK. Try playing around with these values:
This article explains nicely what the differences between CMYK blacks and RGB blacks are, if you need more information: http://www.printernational.org/rich-black-plain-black.php