Stop down

Glossary Terms

To stop down a lens is to reduce the aperture, or increase the f-stop number - reducing the amount of light passing into the camera through by the lens.

This is done:

• to reduce the exposure (or compensate for changing to a slower shutter speed, keeping the exposure constant),
• to increase the depth-of-field, or,
• in an SLR camera, to switch from the aperture fully open (for viewing/focusing) to the taking aperture (for depth-of-field preview, "stop-down metering", or taking the photo).