Sunday, April 17, 2011

All The Hues That’s Fit To Print

Whenever I’m using a complicated piece of software, I find it’s invariably the things that I ignore that turn out to be the most important.

The Blob

When a strange, grey blob-shape appeared between my scrollbars in Inkscape about 18 months ago I completely ignored it and carried on drawing and colouring in. Not only was it vitally important, but if I had only been curious enough to find out what it was sooner I would have discovered a whole new and fascinating world: colour management.

I’ve never had enough money to own a colour printer; I only have a monochrome laser printer which I use very sparingly as a toner cartridge is almost third of my wife’s monthly salary. So I’d never really thought about colour printing until I started designing covers for Retro Software. Dave Moore would sometimes ask me to change this colour or that colour as “it looked awful when printed out”, I’d grumble and change the colour and that would be as far as my interest in printed colour would go.

If I kept myself up to date a little more dilligently I would have realised that that little blob-shape would have allowed me to see what my designs would look like when printed right there in Inkscape.

Colour management seems like too much faff to bother with at first, but is actually pretty simple. When you’re designing on screen, you’re working with light. Light is “additive” – every time you mix colours together you get a lighter colour.  This is usually illustrated using the famous “light spots” you may remember from school (or college):

Avez Vous Le Tempo?

So, for instance, cyan looks lighter than the green and blue you mix together to make it.

When you print you’re working with inks, which get darker as you mix them together. So, for instance, the colour blue is much darker than the cyan and magenta inks you mix together to make it.

The upshot of all this is that there are (quite a lot of!) colours you can show on your monitor that you simply can’t reproduce in print. Pure blues and pure greens that look vivid and exciting on screen look like faded socks and mouldy cheese when printed out.

The precise range of colours you can use on a printer depends on the type of printer you are using. A colour newspaper press can print a far narrower range of colours than the one used to produce a colour magazine.

Conversely, a printer can produce darker colours than you can reproduce on a screen. And each model of scanner, monitor and digital camera has its own quirks as to the range, or gamut, of colours they can deal with.

A horseshoe, apparently

Hence the blob – the blob-shaped icon was based upon the standard horse-shoe shaped graph used to illustrate colour spaces.

The solution to the problem of differing colour gamuts was the creation of a file format called an .icm file. Each .icm file contains an ICC profile which describes the colour gamut of a monitor, printer, camera or scanner. This means that provided you have an .icm file for your monitor and a .icm file for the printer you want to use, your graphics program should be able to use them to show you on screen what your output will look like when it’s printed.

Getting hold an .icm file for your monitor is a pain. Professionals have hardware  calibration devices that they use in conjunction with a program like ArgyllCMS in order to calibrate their monitors. Windows users with Adobe software can use Adobe Gamma. The rest of us can make-do by using a tool called lprof and create a profile by eye. You may find you need to adjust the colour temperature of your monitor to 6500K before you calibrate your screen.

If you are using Fedora, Colour Management is very, very easy to set up in Inkscape. First, you have to get a program called lcms using the “Add/Remove Software” tool. Once you have installed it, you simply have to click the mouse a few times in an Inkscape dialog box and that’s really all there is to it.

Settings to see the effect of Colour Management

Here, I’ve just checked the “Simulate proofing on screen” and chosen a printer .icm in the “Device Profile” box. The display profile should be the profile of your monitor – I haven’t generated one yet so I'm using sRGB.

The Blob In Colour

The blob-shaped icon now springs to life. It is not only in glorious colour but it has also become a button; pressing it has interesting results. Here is my drawing without pressing the blob-shaped button:

Living Colour on screen…

And here is my drawing with it pressed in:

…but the blue and green won't look as good printed!

This is a huge help when designing, as I can now see what my RGB designs will look like when printed out in CMYK.

There is a lot more to the subject of colour management, even in Inkscape. You’ll have to do a bit of research on the web to get to know which .icm profiles to use and the best workflows for CMYK output. But hopefully I've encouraged you to at least have a play!

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