Why what you see on screen isn’t what you get when you print.
It can be confusing when you’re looking at a design on your monitor screen, because the colours you see on the computer screen won’t be the identical to the colours you get when it’s printed out – either printed on your work printer or at a commercial printers. But why?
Well, the computer monitor displays pictures in a format that’s known as RGB – that is, the pictures are made up of tiny Red, Green and Blue dots which combine to display pretty well any colour.
Printers don’t use RGB to create an image, they use Cyan, Magenta, Yellow and Black (or CMYK). So there’s a discrepancy there for a start. When a commercial printer makes up a colour, they use an agreed scale of colours called Pantone to achieve an accurate colour. If you specify a particular pantone reference to a printer, they’ll be able to match the colour exactly.
However, only very expensive computer monitors (usually the ones designers use) can display true pantone colours. So the chances are that your desktop monitor won’t be able to. Unless they’re calibrated to display print-ready pantone colours, the colours you will get will be different from the ones that are printed out.
And the colours printed out by your desktop laser printer will be different from the colours printed out by a commercial printer working to pantone references too. That’s because your desktop printer is unlikely to be calibrated to an accurate CMYK pantone standard.
But it’s not just colour accuracy of the screen that’s at fault. The brightness and contrast of your monitor will slightly alter the colours seen by the eye too.
All of which is why we tend to use printed colour proofs for colour-critical print jobs – and not a PDF version that you see on screen.