Why colour shifts from your screen to the printing press

April 8th, 2015

I have a lot of clients who are surprised that the colour of something designed - shifts from one media to another. I wanted to write a little about why this happens and my own experiences with colour shifting. When I was in college, I learned about colour gamut - or the range of colour that we can perceive. I learned that the human eye can see the most colour - more than we can reproduce using a screen or a printer.

If we used a physical object to loosely represent how much colour the human eye could see - lets say it would be the size of a watermelon - the largest gamut of colour.

The next largest would be what you see on a monitor or RGB colour - comprised of red, green and blue beams of light. This colour gamut might be the size of a cantaloupe.

Printers and printing presses come last in the gamut of colour they can reproduce - the colours used on a printing press are CMYK - cyan, magenta, yellow and black inks. Lets say this colour gamut would be the size of a baseball.

So - why is colour gamut important? Well - what we see on screen in RGB colour often can't be reproduced exactly in CMYK colour - why? Because RGB colour has a larger colour gamut - you can see this when you are in a program like Photoshop and you have vibrant colour photo, when you covert the file from RGB to CMYK for printing - the entire photo dulls down. Certain colours are lost because they simply can't exist in the CMYK gamut.

So an image on screen often looks different than the final printed product. There are ways to make them look closer - but often certain brilliant colours will be lost.

BUT! Printing presses do have a way of bringing some colours back, by using spot colours (also known as Pantone colour). Designers can add a spot colour into your printing file. Lets say you had an image of an amazing bright red sports car and you want the colour to really pop when it printed - a designer could isolate that colour and replace it with a custom mixed spot colour - to help brighten the car and make it stand out. Printers also have the ability to add varnish to the printed piece to add or take away shine - something you can't do on a screen.

The great thing about spot colour is that they can be many things: fluorescent, metallic, pastel etc. And can punch the colour up in an image, and create certain colour that are even outside of the RGB gamut.

Colour on screen will often look more vibrant - but the printer has a few tricks they can use to add back some of that "colour" that was lost in the RGB to CMYK conversion. Understanding the limitations and possibilities of each colour gamut allows a designer to offer the best solutions to his or her client.

So - the next time you get a printed piece that closely matches your on-screen version - be happy - your designer just made magic happen for you!

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