Cameras & f-Numbers

Aperture, exposure and pinholes

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• f-number $N = f/D$; brightness $\propto 1/N^2$; each stop halves the light.
• Wide apertures give shallow depth of field; small apertures keep more sharp.
• The best pinhole is about $1.9\sqrt{f\lambda}$ across.

Steps

1. The f-number
2. Quarter the light
3. Depth of field
4. The best pinhole
5. Reading an f-number
6. Phone cameras