PhotographyLesson 2 of 3 in the course Exposure

Optical and Photographic Aperture: Stops, Exposure, and Image Quality

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces aperture as a concept in optics and distinguishes the aperture from the structures that control light.

In an optical system, the aperture is the opening that primarily limits the light passing through the system. A lens, mirror, or more complex arrangement uses this opening to determine which rays from an object point can reach the image plane and come to focus.

All flashcards

What is the f-number of a photographic lens?
The ratio of focal length to entrance-pupil diameter: N=f/DN=f/D.
What is a lens's maximum aperture?
Its widest opening, described by the lowest available f-number.
What is a field stop?
A stop that limits an optical system's field of view.
What is a sampling aperture?
An opening or time interval over which a signal or image is sampled.
What does image-space telecentricity mean?
Image size is insensitive to the image-plane location.

Quiz questions

  1. In aperture-priority mode, what does the photographer choose?Answer: The aperture; the camera selects an appropriate shutter speed.
  2. At the same focal length and with equal transmission, how does f/2 compare with f/4 in admitted light?Answer: It admits four times as much light.
  3. In an optical system, what does a field stop primarily limit?Answer: The field of view.
  4. In a telecentric optical system, what results when the aperture stop is at the front focal plane of a lens?Answer: Image-space telecentricity.
  5. For a circular entrance pupil, how does its area change when its diameter doubles?Answer: The area becomes four times as large.

Based on the Wikipedia article Aperture, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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