Because signage is big, you images should be big enough to be
printed onto a sign without losing resolution and creating pixel
problems.
Most signage printing companies use CMYK digital printing (also
known as 'wide format' or 'large format printing'.
Take you
photo in the highest possible pixel setting on you digital
camera. Store this file as a .jpeg setting. Keep your photo in
RGB until you are ready to manipulate your graphic design into
your layout.
Once your photo is ready for sign design, create
a new file in CorelDraw, Illustrator, Photoshop, In Design etc
and work in the color mode: CMYK (C-cyan, m-magenta, y-yellow,
k-black) The letter K is used for the black ink. This is an
industry standard to avoid any confusion with RGB (b-blue)
File Resolution: Aim for 16mg per m of finished banner sign
size. Example, if you file is approx 32mb, you could create a
photo sign of two square metres without any printer requiring
internal work on the file. That is, you file is 'ready for
print'.
Exceptions: IF you are working with text only, or
vector (line art) then you can reduce your file size to 16kb.
Vector graphics are the best for sharpness. If your using
Photoshop, create all the photo work in a pixel format, and
'place' into your file .eps, .ai or .cdr lines, texts etc. This
will print better.
Work in 150 dpi (computer file) or higher.
Using a 72 dpi is for your computer monitor, not commercial sign
printing in large format CMYK.

If your file looks like this at
zoom, then it is ok for printing.
