Contrast ratio results for xt

Black
Contrast ratio	670:1
Monitor model	xt
Submitted	16 Dec 2009 05:11 CET, by 69.145..
Camera model	Canon PowerShot A620
Processing remarks	Warning: image file 2: exposure time below 1/500 sec is unreliable. Try increasing the EV compensation. image file 2: Note: image seems to be noisy. Try reducing the ISO setting or increasing the exposure time.
Screen photo	[open image]
Luminance	0.62 cd/m2
Luminance spread	0.1 cd/m2 (2 standard deviations)
Exposure value	–1.77 stops (aim for –2 to –3)
Exposure spread	0.24 stops
Area used for calculation	0.494 x 0.494
Camera settings	Exposure time: 0.8 ISO: 400 F-number: 2.8 Focal length: 34.2 mm (35 mm equivalent) Exposure compensation: 0
White
Screen photo	[open image]
Luminance	413 cd/m2
Luminance spread	179 cd/m2 (2 standard deviations)
Exposure value	–2.34 stops (aim for –2 to –3)
Exposure spread	0.64 stops
Area used for calculation	0.494 x 0.494
Camera settings	Exposure time: 1/1244 ISO: 400 F-number: 2.8 Focal length: 34.2 mm (35 mm equivalent) Exposure compensation: 0

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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.