Design Nomenclature / Color
Purkinje shift
Also called Purkinje effect, scotopic shift
- Color
- Light & Optics
- 2D & 3D
As light falls and vision hands over from cones to rods, peak sensitivity moves from about 555 nm to 505 nm. Reds darken toward black and blues hold their luminance — which is why a red geranium that outshone the foliage at noon goes flat and dead at dusk while the leaves stay legible.
In practice
The practical case is dark interfaces and night instrumentation: red on a dark ground loses more apparent luminance in dim viewing than its measured contrast ratio predicts.