The Tenuous Link

Two computer screens, the same picture on each. But it looks different. And on both, the image is different from a print of the picture. The colours are different, and the dark areas have detail on one, and are just black on the other. None of which is really a problem unless (a) I am trying to edit a photograph so it looks as good as possible when I print it, or (b) I'm using both monitors at the same time.

OK, (b) is more of an irritation than a problem, but how can I get everything looking right? Well, in my case, a lot of wasted time, and then spending some money on the problem. First how I spent my money ...

Pantone ColorVision Spyder2Pro is a "Professional Color Calibration System for CRT and LCD displays" according to the box. It cost me £200 from Amazon.co.uk. Pricey? Depends how obsessive you are, or how much money you spend on printed pictures.
Amazon.com or Amazon.co.uk?

The Spyder2 is a hardware gadget that plugs in to your computer's USB port and attaches to (or rests on) the front of your monitor. The bundled software then displays a sequence of colours, and the Spyder measures the actual colour on the screen. After the measurements, the software loads correction curves in to your graphics card so that everything you look at is correct.

Unfortunately, "correct" can mean many things; I aimed the Spyder at the sRGB colour space, which is what pictures on the web should be optimised for. An added complication comparing the colours on the screen with the colours on a print is that light shining on white paper will affect the apparent colour of the paper; typical room lighting has a colour temperature of 5000 K, sRGB specifies 6500K. I used the Spyder to make me another profile aimed at 5000 K, and it's easy to use the software to switch between them to "print proof". Also, the 5000 K profile seems a little easier on my eyes when I'm working at night.

The biggest difference after calibration is that when I look at a website that describes how to calibrate your screen visually, everything looks good. The grey blocks don't have a colour cast, and they do disappear into the stripy backgrounds when I take off my glasses. I can tell the difference between dark grey and black, and between light grey and white. Printed pictures look pretty close to what's on the screen, and that's before I've started calibrating my printer - but that's a whole other wasted afternoon ;-)

So why was this so hard without the hardware? I did spend time with Adobe Gamma, and WiziWYG, but decided that the Gamma curve is a myth. My monitor doesn't have a perfect response, and the curve has kinks in. In addition, the red, green, and blue colours have different responses, and it's important to get the black and white points set correctly. If you have a problem with this, you aren't going to be able to fix it by squinting at striped patterns. Spend the money.

Did you know you can get special calibrated light bulbs for looking at your prints under? This guy claims to use one, and links to some useful test patterns too:gamma evaluation at 3 brightnesses and a Java applet to evaluate gamma at any brightness.

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Problems:

• For my main LCD, I to get a visually correct gamma of 2.2 I had to ask the software to calibrate for a gamma of 1.9.
• You lose a little screen brightness after the correction.
• My graphics card or monitor was causing some clipping of the brightest white values on the screen. The Spyder2Pro didn't fix that automatically, but does have a precalibration that helped to fix it by hand.
• Even using a calibrated light-bulb (I'm joking -- I don't really have one), print colours can't match exactly to screen colours all the time because of the different ways screen and printer make the colours. Printers mix magenta, cyan, and yellow inks; monitors mix red, green, and blue light.

Differences between Spyder2 and Spyder2Pro:

• The feature matrix on the ColorVision web site says the Pro hardware is "best" callibration accuracy. Is there really any difference?
• The software included with the Pro version lets you define your own target profiles. I needed to use this to get a gamma 2.2 profile that looked right for my main LCD monitor.
• The software in the Pro version allows calibration of multi-monitor setups (dual-head: two monitors on one PC).
• The license included with the Pro version states that you are allowed to calibrate all computers on a site (and 10 laptops -- how generous!).
• More software is provided. I only used the Nik Effects plugins in PhotoShop Elements. Once.

Differences between the old fashioned Spyder and the new Spyder2:

• A plastic baffle is supplied with the hardware, and a counterweight, to enable use with LCD screens.