Contrast ratio of IBM Thinkpad T23 (1024x768)

Black
Contrast ratio	139:1 (edge: 168:1)
Monitor model	IBM Thinkpad T23 (1024x768)
Submitted	04 Mar 2008 19:12 CET, by 82.139..
Camera model	Canon PowerShot A540
Processing remarks	Note: image file 2: suggested exposure time: 1/430 s (Set EV to +0.6)
Screen photo	[open image]
Luminance	0.79 cd/m2
Luminance spread	1.31 cd/m2 (2 standard deviations)
Exposure value	–2.88 stops (aim for –2 to –3)
Exposure spread	3.46 stops
Area used for calculation	0.495 x 0.495
Camera settings	Exposure time: 1/4 ISO: 400 F-number: 2.6 Focal length: 34.3 mm (35 mm equivalent) Exposure compensation: 2
White
Screen photo	[open image]
Luminance	109 cd/m2
Luminance spread	15 cd/m2 (2 standard deviations)
Exposure value	–1.07 stops (aim for –2 to –3)
Exposure spread	0.2 stops
Area used for calculation	0.495 x 0.495
Camera settings	Exposure time: 1/159 ISO: 400 F-number: 2.6 Focal length: 34.3 mm (35 mm equivalent) Exposure compensation: 2
Black at screen edge
Screen photo	[open image]
Luminance	0.65 cd/m2
Luminance spread	1.1 cd/m2 (2 standard deviations)
Exposure value	–2.89 stops (aim for –2 to –3)
Exposure spread	3.6 stops
Area used for calculation	0.495 x 0.495
Camera settings	Exposure time: 0.3 ISO: 400 F-number: 2.6 Focal length: 34.3 mm (35 mm equivalent) Exposure compensation: 2

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The luminance values in cd/m2 are not very reliable, since camera sensitivities can easily differ up to 50% from their nominal value. Typically, the real luminance is 30% lower than this number. The area used for calculation is chosen such that it corresponds to a viewing angle of ±14° horizontally and ±10.5° vertically, which is equivalent to viewing the screen from a distance of about 1.5 times the diagonal size.

Unfortunately, there is a lot of variation in how cameras use EXIF settings. If photos from your camera your produce unusable results, try coming back in a few days. I review submitted pictures regularly and try to fix problems.