Film Sensitivity and Grain
The size of silver halide grains in the emulsion affect film sensitivity; which is related to granularity because larger grains give film greater sensitivity to light. Fine-grain film, such as film designed for portraiture or copying original camera negatives, is relatively insensitive, or "slow", because it requires brighter light or a longer exposure than a "fast" film. Fast films, used for photographing in low light or capturing high-speed motion, produce comparatively grainy images.
Kodak has defined a "Print Grain Index" (PGI) to characterize film grain (color negative films only), based on perceptual just-noticeable difference of graininess in prints. They also define "granularity", a measurement of grain using an RMS measurement of density fluctuations in uniformly exposed film, measured with a microdensitometer with 48 micrometre aperture. Granularity varies with exposure — underexposed film looks grainier than overexposed film.
Read more about this topic: Film Speed
Famous quotes containing the words film, sensitivity and/or grain:
“You should look straight at a film; that’s the only way to see one. Film is not the art of scholars but of illiterates.”
—Werner Herzog (b. 1942)
“...some small boys came out of the city and jeered at him, saying, “Go away, baldhead! Go away, baldhead!””
—Bible: Hebrew, 2 Kings 2:23.
Elisha--proving that baldness has been a source of sensitivity for centuries, Elisha cursed them and they died.
“Grow your tree of falsehood from a small grain of truth.
Do not follow those who lie in contempt of reality.
Let your lie be even more logical than the truth itself,
So the weary travelers may find repose.”
—Czeslaw Milosz (b. 1911)