- Raiders of the Lost Ark (Wikipedia)
Raiders of the Lost Ark is a 1981 American action-adventure film directed by Steven Spielberg from a screenplay by Lawrence Kasdan, based on a story by George Lucas and Philip Kaufman. Set in 1936, the film stars Harrison Ford as Indiana Jones, a globetrotting archaeologist vying with Nazi German forces to recover the long-lost Ark of the Covenant which is said to make an army invincible. Teaming up with his tough former romantic interest Marion Ravenwood (Karen Allen), Jones races to stop rival archaeologist René Belloq (Paul Freeman) from guiding the Nazis to the Ark and its power.
- f-number (Wikipedia)
An f-number is a measure of the light-gathering ability of an optical system such as a camera lens. It is calculated by dividing the system’s focal length by the diameter of the entrance pupil (“clear aperture”). The f-number is also known as the focal ratio, f-ratio, or f-stop, and it is key in determining the depth of field, diffraction, and exposure of a photograph. The f-number is dimensionless and is usually expressed using a lower-case hooked f with the format f/N, where N is the f-number.