Purkinje effect  From Wikipedia, the free encyclopedia Jump to:
navigation, search  The Purkinje effect (sometimes called the
Purkinje shift, or dark adaptation and named after the Czech
anatomist Jan Evangelista Purkyně) is the tendency for the peak
luminance sensitivity of the human eye to shift toward the blue
end of the color spectrum at low illumination
levels.[1][2][page needed]  This effect introduces a difference
in color contrast under different levels of illumination. For
instance, in bright sunlight, geranium flowers appear bright red
against the dull green of their leaves, or adjacent blue
flowers, but in the same scene viewed at dusk, the contrast is
reversed, with the red petals appearing a dark red or black, and
the leaves and blue petals appearing relatively bright.  The
sensitivity to light in scotopic vision varies with wavelength,
though the perception is essentially black-and-white. The
Purkinje shift is the relation between the absorption maximum of
rhodopsin, reaching a maximum at about