Stiles-Crawford Effect

The Stiles-Crawford effect of the first kind (SCE-I) describes the perceived difference in brightness when a light beam travels through the open pupil . The perception of brightness resembles a Gaussian curve , ie the perception of brightness is weak at the nasal and temporal edges of the pupil and highest at the point of best vision (near the center of the pupil).

The curve is described as follows: Visibility ${\ displaystyle \ eta (r, \ lambda) = 10 ^ {- \ rho (\ lambda) (r-r_ {0}) ^ {2}}}$

${\ displaystyle \ rho}$ is the direction factor of the cones, which describes whether the curve is flatter or steeper. Since there are three different types of cones on the retina and in different places, different values result for each different wavelength . is the center of the pupil (not to be confused with the point of best vision) and r describes the measuring point on the pupil at a distance from the center of the pupil. The visibility depends on the measuring point on the pupil related to the pupil center and the incident wavelength. ${\ displaystyle \ rho}$ ${\ displaystyle r_ {0}}$ ${\ displaystyle \ eta}$

The Stiles-Crawford effect of the second type (SCE-II) describes an additional perceived change in color when a monochromatic light beam moves away from the center of the pupil. This color shift was published by Stiles in 1937. But since there is a fundamental connection with the publication of 1933, we speak of the Stiles-Crawford effect of the second type today. The current theory suggests that the effect disappears with monochromatic light as the bandwidth decreases.

Both effects occur in daylight vision. The reason lies in the fiber properties of the cones, which are mainly located in the fovea centralis of the retina and are responsible for color vision. Light entering the edge of the pupil falls on the fovea at an angle of approx. 10˚. As a result, less light is coupled into the cones and this light is perceived as weaker, less bright.

The optical Stiles-Crawford effect (O-SCE) does not describe the SCE on the retina, but rather the light reflected by the retina is measured outside the eye.

literature

WS Stiles, BH Crawford: The luminous efficiency of rays entering the eye pupil at different points. In: Proc. Roy. Soc. B. Vol. 112, 1933, pp. 428-450.
AW Snyder, C. Pask: The Stiles-Crawford-Effect - explanation and consequences. In: Vision Research. Volume 13, 1973, pp. 1115-1137.

Individual evidence

↑ WS Stiles: The luminous efficiency of monochromatic rays entering the eye pupil at different points and a new color effect. In: Proc. Roy. Soc. B. Volume 123, 1937.
↑ B. Vohnsen: On the spectral relation between the first and second Stiles-Crawford effect. In: Journal of Modern Optics. Volume 56, No. 20, Nov. 2009, pp. 2261-2271.

[1] WS Stiles: The luminous efficiency of monochromatic rays entering the eye pupil at different points and a new color effect. In: Proc. Roy. Soc. B. Volume 123, 1937.

[2] B. Vohnsen: On the spectral relation between the first and second Stiles-Crawford effect. In: Journal of Modern Optics. Volume 56, No. 20, Nov. 2009, pp. 2261-2271.