Field adaptation in the horizontal cells. Rushtonian transformation.

In the presence of a steady ambient illuminance there occur two changes in the horizontal-cell incremental response; 1) The incremental sensitivity decreases which is WeberFechner like phenomena. 2) The response becomes faster . The response to a modulation around a mean is linear: This is a piecewise linearization. With the classical spot-annular experiment, a steady annulus of light increases the incremental sensitivity, makes the response faster, and linearizes the response. I propose to refer to the set of changes as the Rushtonian transformation which is an extension of Rushton's idea of field adaptation1).