Light response is nonlinear
Our visual system has a large dynamic range
•We
can resolve both light and dark things at the same time
•One
mechanism for achieving this is that we sense light intensity
on a logarithmic scale
–an
exponential intensity ramp will be seen as a linear ramp
•Another
mechanism is adaptation
–rods
and cones adapt to be more sensitive in low light, less sensitive
in bright light.