Resolution and colour: RGB, CMYK and 300 dpi

Customers design on bright screens and expect the print to match. It rarely does unless someone checks the file first. Resolution and colour mode are the two checks that save the most reprints.

Resolution

For photos and images, aim for about 300 dpi at the size they will print. A 1,200 pixel image is enough for 10 cm at 300 dpi, but looks soft at 30 cm. Logos and text should be vector where possible, so they stay sharp at any size. Large items seen from a distance, such as banners, can use lower resolution.

RGB and CMYK

Screens mix light (RGB); presses mix ink (CMYK). Some bright RGB colours, especially vivid greens, oranges and electric blues, cannot be printed with four inks and come out duller. Convert RGB files to CMYK with a proper profile, and show the customer the result on the proof.

Rich black and fine text

• Large black areas look deeper as a rich black (black plus some cyan, magenta and yellow).
• Small text and thin lines should be plain 100% black, so they do not blur if the plates shift slightly.
• Watch total ink coverage on uncoated stock: too much ink dries slowly and can set off onto the next sheet.

Spot colours

When a brand colour must match exactly, it may be specified as a Pantone or other spot colour. On a four-colour job it will be converted, and the match will be close but not exact. Agree with the customer whether close is good enough, or whether the job needs a spot ink.

Soft proofing

Before the job prints, send a PDF proof converted to the output profile, and say plainly which colours will shift. A customer who has been told in advance accepts a small change; one who sees it for the first time on delivery asks for a reprint.

A note for repeat jobs

For customers who reorder, keep the converted file and a printed sample of the approved job. Matching the next run to a physical sample is far easier than matching it to a screen, and the customer sees the same colour every time.