Figure 1.

Luminance calibration of two iPad tablet screens: iPad2 (gray circles) and iPad3 (unfilled diamonds). Both return similar gamma functions (2.4, lines) but the iPad2 tablet is consistently dimmer than is the iPad3 due to its lower amplification. This results in a dimmer background level for testing on the iPad2 (4.2 vs. 5.0 cd.m⁻²) but has no practical impact on the dynamic range (30.8 vs. 31.4 dB) as the smaller steps are proportionately scaled by the higher amplification constant.