Contrast ratio results for iMac 27" (Late 2012)

Black
Contrast ratio	900:1 (edge: 1124:1)
Monitor model	iMac 27" (Late 2012)
Submitted	26 Mar 2024 08:05 CET, by 73.140..
Camera model	Canon EOS REBEL T3i
Processing remarks	Warning: image file 3: Overexposed. Please decrease the shutter time. Note: image file 3: suggested exposure time: 1.8 s (Set EV to -2.1)
Screen photo	[open image]
Luminance	0.42 cd/m2
Luminance spread	0.31 cd/m2 (2 standard deviations)
Exposure value	–2.36 stops (aim for –2 to –3)
Exposure spread	1.11 stops
Area used for calculation	0.524 x 0.589
Camera settings	Exposure time: 1.6 ISO: 400 F-number: 4 Focal length: 37.7 mm (35 mm equivalent) Exposure compensation: 0
White
Screen photo	[open image]
Luminance	374 cd/m2
Luminance spread	32 cd/m2 (2 standard deviations)
Exposure value	–0.85 stops (aim for –2 to –3)
Exposure spread	0.12 stops
Area used for calculation	0.524 x 0.589
Camera settings	Exposure time: 1/197 ISO: 400 F-number: 4 Focal length: 37.7 mm (35 mm equivalent) Exposure compensation: 0
Black at screen edge
Screen photo	[open image]
Luminance	0.33 cd/m2
Luminance spread	0.05 cd/m2 (2 standard deviations)
Exposure value	–0.36 stops (aim for –2 to –3)
Exposure spread	0.24 stops
Area used for calculation	0.524 x 0.589
Camera settings	Exposure time: 8 ISO: 400 F-number: 4 Focal length: 37.7 mm (35 mm equivalent) Exposure compensation: 0

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.