1. Represents inherent density of the film base, plus expected fog.
“Toe” portion represents areas of the film that are usually too light to be diagnostic.
“Straight line portion” represents useful density range; contains majority of diagnostic information.
Shoulder portion represents areas of the film that are usually too dark to be diagnostic.
“Dmax” represents the maximum amount of density the film can record.
Film “A” arrives at the pre- determined density (speed point) with less exposure than film B. Film A is therefore considered faster.
Film “A” with a steeper, more vertical slope, demonstrates higher contrast than film B.