Exposure dial

A thumb wheel for the three numbers that make an exposure. Drag it, scroll it, or use the arrow keys. With detents on it snaps to the nearest third of a stop and carries the speed of your release into the spring; with them off the same spring lands wherever the flick carries it.

The scales are the sequences cameras actually print: 1/4000 to one second, f/1.4 to f/22, ISO 100 to 6400, in thirds. Every third value is a full stop, which is what decides the tall ticks.

The ticks are laid out with a CSS variable instead of measurements, so the dial is correct on the first paint and at any width.

Keyboard and access

Keyboard

The dial is a focusable slider. Arrow keys move one third of a stop, Page Up and Page Down move a full stop, and Home and End jump to the ends of the scale. Horizontal scrolling turns it, and vertical scrolling does too once it has focus.

Screen readers

It is exposed as a slider named after the scale, with a value text spoken the way you would say it, like "1/250 second" or "ISO 400". The animated readout is hidden and replaced by the plain text.

Reduced motion

With reduced motion the dial jumps straight to its value without a spring, and the readout changes without rolling.