I have devised a method of measuring gamma without the need for special equipment – a way of setting up a display which is independent of the operating system. Commercial profiling systems don’t seem to provide software for Ubuntu (Linux).
There are several charts and applets on the web which rely on subjectively matching stripes and grey patches but whilst my method uses the same principle the match is based on measured luminance rather than on human judgement.
The method uses test targets displayed in Photoshop (or other image/graphics processing application) – which has the advantage of predictable colour management – and hardware costing about £10 (US $16) including the meter!
I have just added a page describing the system. Have a look and feel free to comment.
Since my previous post and uploading the page on this subject I have noticed that the test cards look different in different browsers. In IE and Chrome the shadow card shows a just perceptible difference between the ‘4’ patch and the ‘0’ background. In Firefox, Seamonkey and Safari there is a more noticeable difference. I believe this is because these last three are implementing colour management and are showing the card ‘correctly’. This was confirmed by viewing the file in Photoshop and selecting either ‘don’t color manage’ or using the embedded profile (sRGB).
I should point out that since the page was originally uploaded I have replaced the jpeg test cards with .png files so as not to confuse matters with embedded profiles. This does not in any way invalidate the above statements but it does mean that to view the files correctly in Photoshop a profile (sRGB) should be assigned and colour management applied on opening. The appearance of the test cards (now without embedded profiles) in the listed browsers is unchanged, suggesting that those browsers implementing colour management are assuming an sRGB profile.