Digital Cinematography, 2nd Edition

164 Chapter 7

Figure 7.73 Diffraction through wide and narrow

apertures.

Diffraction occurs when wavesencounter an

obstacle or a very small aperture. It is the bending

of light waves around the corners of an obsta-

cle or aperture into the region of shadow of the

obstacle. Similar effects occur when a light wave

travels through a medium with a varying refrac-

tive index such as glass or an aperture. Diffraction

in lenses shows up as arbitrarily softer pictures at

deeper stops, diminishing the benets of added

depth of eld that stopping down should intui-

tively yield. Diffraction sometimes creates odd

artifacts ...