Colour is in the eye of the beholder

Posted on November 13th, 2013 | Tags: Technical

colouring-pencils-small

We do a lot of colour printing, and I do mean a lot, and the quality of what our machines produce is very high. Occasionally we do get someone who says ‘but it didn’t look this colour on the screen’ when we give them the prints. This becomes critical when people are trying to match company colours or want a colour feel to an image. So why does it happen and what can be done to ensure that it doesn’t become a problem.

The science of colour (how it is seen, how it is produced, how the underlying media effects how the colour looks, even what you should call a particular shade) is a massive subject and is far too big to cover in a quick little blog article. (If you are interested you can start at this wikipedia article:http://en.wikipedia.org/wiki/Colour .) There are massive businesses devoted to dealing with the problems of colour, Pantone being the most well known. In this article we will look at the most basic causes of colour problems and how to deal with them. They come down to the following problems: projected and reflected light, RGB and CMYK colours, colour ranges, Pantones and the nature of papers themselves.

Projected and Reflective Light

The most common complaint about colour issues is that the printed copies are ‘darker’ than the original seen on the screen. The cause is that on a computer screen the image you see is projected light, often with it set too bright too, while on the page you see the image from reflected light. The colours are going to be darker because the light is weaker than what you see on the screen. If you want a graphic example, it’s comparing looking directly in to a lit torch compared to looking at the light from torch reflected in a mirror. From the anecdotal evidence I’ve collected it seems to be about a 10% brightness difference.  While we can adjust the brightness of the printed image (in total) when we print it, it does pay to remember that what you see on the screen will always be brighter than what you see on the page.

RGB and CYMK

Red, Green and Blue are the three primary parts of light and the ratio and strength of each colour makes every colour you see. You start at R0% G0% B0% which is black and add to each of the three colours till you get white at R100% G100% B100%. This is how computers, cameras and tv’s work to make images. Most printers, however, rely on Cyan Yellow Magenta to make colour you see, with black being C100% Y100% M100% and reducing the amount of each to you get white at C0% M0% Y0%. (The K in CYMK is for blacK because it’s more cost efficient to use small amount of black to darken a colour than extra CYM and the pure black looks blacker than the ‘rich’ black of CYM). The issue comes from translating from the RGB of computer images to the CYMK of the printing system. While they spend huge amounts of time and money writing software to deal with the issue there will always be some small colour drifts – think of it as “lost in translation.”  Unfortunately, most Microsoft products work in RGB rather than CMYK.  When designing things that have special colour needs you should always use a tool that support CMYK.  For even more accuracy, you should use a “colour profile” for the machine that the material will be printed on (yes, they all vary ever-so-slightly) – we can supply you with files for our equipment if you need it.

Colour Ranges

I’ve already talked about RGB and CYMK and you would have read that all the colours we see are made up by mixing different amounts of the primary colours. Depending on who you talk too we can see about 10 million colours. Display technology has made strides where your computer can display most if not all of these colour. Printing technology is still catching up so they can’t make the same range of colours. In practical terms most printers have a much more limited colour range – counted in the tens of thousands not millions of colours, and there are some shades each printing technology will have issues with no matter what you do (for example, no digital printer can recreate Cadburys’ purple). Interestingly, digital printers have a higher colour range than CMYK offset printers, but the key point here is that there are limits.  From a design perspective it is good to design for your target printing technology – there is no point is using a colour that just can’t be matched without great expense!

Pantones

This one is for the designers out there. Pantones are a double edge sword for printers. Once upon a time in the ink and plate days, Pantones were vital because that mean there was a single standard to pick out the inks needed to do the printing job. These days the only way to properly use a Pantone colour is on an offset printer with a special plate and ink tank for that specific colour (this is usually done on massive 10-plate presses that cost millions).  But if you are using digital or lower-cost offset printing methods then this is not available to you.  What can be a problem is that often designers will use a Pantone palette designed for one style of technology and then send it to be printed using a different system all together with a resulting colour change as the printer tries to match a colour setting it isn’t designed to handle. The easiest way for designers can avoid this is just convert the Pantones colours in to their CYMK versions and leave the printer to take care of the rest.

Nature of papers themselves

I’ve discussed the effects of the nature of paper can have on printing in the Coated versus Uncoated post in a different article. The only addition I will say here is that because reflected colour relies on the paper to form part of the colour base, the minute you stop using ultra white paper you will have changes in the colours printed on it. We do have ways to compensate for it to a degree, but in the end there will be some colour changes we can not control.

As I said at the start of this article, the science of colour is far too big to deal with in a single blog post. What I will say is that for the majority of people, all the issue I’ve talked about here are never big enough to cause an issue with the work we print for them. If you are concerned, then we are always more than happy to print samples to take away and compare to your source before committing to a print job. In fact we will always recommend doing it where colour is important as it’s often the final tweak needed to turn something good to great.