An example: the lower the color- or brightness contrast between printed text and a sheet of paper, the more difficult it is to read the text. The same applies to small font sizes.
Fundamentally, visual performance increases abruptly with increasing illuminance. However, above 92.90 fc (1,000 lx) it increases only slowly to then finally decrease at very high illuminances due to the occurrence of glare.
1. Visual acuity S according to age (nominal values)
2. Influence of illuminance E on visual acuity S of normal-sighted observers
3. Influence of illuminance E on relative visual performance P for simple (upper curve) and difficult visual tasks (lower curve)