Adelson

A bit heady of a reading.... 

DEFINITIONS:
Low-level vision: our eyes processing of raw visual data.
High-level vision An assumption of what our eyes see based on actual visual data and our experience of similar objects.
Mid-level vision: A mid point between Low Level Visions and High Level Vision.
Luminance is the amount of visible light that comes to the eye from a surface
Illuminance is the amount of light incident on a surface
Reflectance is the proportion of incident light that is reflected from a surface

I think it's fair to assume most of us in everyday life operate in Mid Level Vision most of the time.

I think the best way to understand this is to think of a Computer Monitor displaying a picture.  

Display at LOW LEVEL would be a very pixel-ate/noisy picture without detail.  

Display at HIGH LEVEL would be very shape based, low detail, and mostly inferred.  Similar to rendering an a 3D image in say 3D max prior to applying material to it.  Very crude shapes and contours.  This is very common with young kids who confuse objects based solely on shape and size.  Dog or Horse?

MID LEVEL is the merging of these two levels to create a complete image.