Accelerator Chemical ingredient of developer to speed up the otherwise slow activity of developing agents. Normally an alkali such as sodium carbonate, borax, or (high-contrast developers) sodium hydroxide. Also known as ‘activator’ or ‘alkali’ component.

Acid Chemical substances with pH below 7. Because acid neutralizes an alkali, acidic solutions are often used to halt development – as in stop bath or fixer.

Adaptor ring Narrow threaded ring which fits the front rim of a lens to allow use of accessories of a different (‘step-up’ or ‘step-down’) diameter.

AE Automatic exposure metering.

AE lock (AE-L) Camera control which locks the exposure settings made by an auto exposure programme.

Aerial perspective Sense of depth conveyed by changes ...

Get Basic Photography, 7th Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.