Receptor 
I_{0} * 
Region 
Reference 
Rods 
4.4 log scot. td 
Periphery 

L & Mcone mixture 
4.3 log phot. td 
Fovea 

Lcone 
3.89 log phot. td 
Fovea 

Mcone 
3.89 log phot. td 
Fovea 

*the intensity at which the fractions of unbleached and bleached pigment are both 0.5.
Formulae
(1) Equilibrium bleaching
,
where p is the percentage of unbleached pigment, I is the intensity if the bleaching light in trolands and I_{0} is the halfbleaching constant in trolands.
(2) Short bleaching exposures
,
where p is the percentage of unbleached pigment, I is the intensity if the bleaching light in trolands and t is the time in seconds.
Baker, H.D. & Rushton, W.A.H. (1965). The redsensitive pigment in normal cones. Journal of Physiology, London, 176, 5672.
Campbell, F.W. & Rushton, W.A.H. (1955). Measurement of the scotopic pigment in the living human eye. Journal of Physiology, London, 130, 131147.
Ripps, H. & Weale, R.A. (1969). Flash bleaching of rhodopsin in the human retina. Journal of Physiology, London, 200, 151159.
Rushton, W.A.H. (1972). Visual pigments in man. In Dartnall, H.J.A. (ed.), Handbook of sensory physiology VII/I. New York: SpringerVerlag.
Rushton, W.A.H. (1963). Cone pigment kinetics in the protanope. Journal of Physiology, London, 168, 374388.
Rushton, W.A.H. (1965). Cone pigment kinetics in the deuteranope. Journal of Physiology, London, 176, 3845.
Rushton, W.A.H. & Henry, G.H. (1968). Bleaching and regeneration of cone pigments in man. Vision Research 8, 617631.