Linearity of the camera in ISO setting.

The mean raw RGB response of the three color channels (red, green, blue; shown in corresponding colors) is plotted against the ISO setting after dark subtraction, for two values of exposure time (solid line, circles = ; dashed line, squares = ), and aperture. The lines are linear regressions through non-saturated data points (solid squares or circles; raw dark subtracted values between 50 and 16100); the slopes are 0.99 (R), 0.98 (G), 0.99 (B) for exposure and 1.03, 1.02, 1.04 for exposure. The camera saturated in the red channel at longer exposure; the corresponding data points (empty red circles) are not included into the linear fit.