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Abstract:
The natural world presents our visual system with a wide range of colours and intensities. A starlit night has an average luminance level of around 10-3 candelas/m2, and daylight scenes are close to 105 cd/m2.
Humans can see detail in regions that vary by 1:104 at any given adaptation level, over which the eye gets swamped by stray light (i.e., disability glare) and details are lost. Modern camera lenses, even with their clean-room construction and coated optics, cannot rival human vision when it comes to low flare and absence of multiple paths ("sun dogs") in harsh lighting environments. Even if they could, conventional negative film cannot capture much more range than this, and most digital image formats do not even come close. With the possible exception of cinema, there has been little push for achieving greater dynamic range in the image capture stage, because common displays and viewing environments limit the range of what can be presented to about two orders of magnitude between minimum and maximum luminance. A well-designed CRT monitor may do slightly better than this in a darkened room, but the maximum display luminance is only around 100 cd/m2, which does not begin to approach daylight levels. A high-quality xenon film projector may get a few times brighter than this, but they are still two orders of magnitude away from the optimal light level for human acuity and colour perception.