Digital Video and HD, 2nd Edition

11

Picture rendering

Examine the flowers in a garden at noon on a bright, sunny day. Look at the same garden half an hour after sunset. Physically, the spectra of the flowers have not changed, except by scaling to lower luminance levels. However, the flowers are markedly less colourful after sunset: Colourfulness decreases as luminance decreases. This is the Hunt effect, first described (in 1952) by the famous colour scientist R.W.G. Hunt. Reproduced images are usually viewed at a small fraction, perhaps ¹/100 or ¹/1000, of the luminance at which they were captured. If reproduced luminance were made proportional to scene luminance, the reproduced image would appear less colourful, and lower in contrast, than the original scene.

To reproduce contrast ...