neuroanatomist said:
The alternate method you suggest I'd call measuring DR, as opposed to calculating it. IMO, measuring is the better way to test DR - that gives you an actual test of the usable DR.
About that wedge test... doesn't the measured DR, on the dark side, depend on the size of the wedge? If the criterium is the ability to distinguish two adjacent patches, and that ability is limited by noise, then I would think a 4 times larger intersection would give a factor ~2 more sensitivity (and thus 1 stop more DR; the eye is great in seeing structure among noise). If you have a wedge, it should be easy to test, just put the wedge 4 times further away than you would normally do and see if the DR comes out ~1 stop lower.
In the extreme, if each patch was only one pixel big, then it's clear the measured DR would be much less due to noise. The other extreme would be if two adjacent patches shared the full diagonal of the sensor (for a straight line). That would surely give a much higher "DR".