Screen gamma: Adjust your monitor’s colour with free software

December 21, 2008

More and more photographs are moving on to the screen rather than being printed out.

The screen has become the medium of communication. (There is a book by Fred Pitchen, After Photography, published by Norton and available on Amazon, which is fairly academic on the subject)

The problem is that screens vary tremendously as to the color they show you. Professional photographers realize that if the client is going to look at proof shots on a computer screen, that screen will almost certainly need to be adjusted.

The key to this is gamma.

Gamma is the relationship between the brightness of a pixel (which stands for picture element) as it appears on the screen, and the numerical value of that pixel.

A pixel can have any ‘value’ of red, green, and blue ranging between 0 and 255. Using logic you would work on the basis that a pixel value of 127 would appear as half of the maximum possible brightness and so on. Well it just ain’t so. The relationship, to use a mathematical terms, is not linear it is exponential with gamma being the exponent.

Monitor gamma values range widely depending on the type and age of the screen. Possibly somewhere between 1.4 and 3.2.

The standard for Windows if you are using an LCD screen — one that is thin and flat — should be 2.2. If it is not, all of your pictures will have a color cast. The further away you get from that ideal figure the more color inaccuracy there will be in displayed pictures.

Under Windows a gamma correction is already automatically applied but because most computer monitors do not have a real gamma of 2.2 you need to apply an additional correction.

Uncorrected monitors abound.

I once tested 30 at the Sydney Morning Herald and every single one was way off with the fairies, which may come as no surprise to anyone who knows that newspaper.

An uncorrected monitor is OK for word-processing, reading e-mail, or even casual web browsing but is disaster if you are looking at or working with images.

If you are working with a CRT monitor — the fat ones which look as if they contain a television tube — you may find 2.2 too dark and will work better with something a little lower — perhaps 1.8. You can experiment to see which is best.

Note that the majority of graphics professionals and pre-press proofing rooms use a gamma of 1.8 but, mainly, they are using CRT screens. Where they are using LCD screens, as on a notebook and increasingly on desktop machines, 2.2 is the best figure to go with.

We need not be fanatical about this. A compromise value of 2.0 — which is incidentally midway between the Mac and the PC — works if you are preparing images solely for web publishing.

If you have a full version of Photoshop then from version 3 onwards, it comes with a little utility called ‘Adobe Gamma’. In fact, this has not had great reports as to its quality and perhaps you will be better off using QuickGamma of which more in a moment.

If you use Paintshop Pro you can follow the instructions which are in File/Preferences/Monitor Gamma.

DarkAdapted,, is a free program that has had good reports. But the easiest to use — simple is good — is Quick Gamma, which is what I use on all of my computers.

With QuickGamma you can calibrate your monitor to a gamma value of 2.2, which, in conjunction with the automatic gamma correction, gets it right for every monitor.

More information and detailed instructions on how to use QuickGamma are available by pushing the Help button in QuickGamma.

The program is free as in at no charge, which is a good price. You can get it at QuickGamma and you should do so. Then check your screen every two or three months.

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