Glossary
Bellows extension
Light loss that happens when you focus close on a view camera with extending bellows.
When a large-format lens is racked out for macro or close-focus work, the distance between lens and film grows. Light spreads over a larger area and gets dimmer at the film plane, which means your meter reading is no longer accurate without a correction. The bellows factor counts the number of stops of correction needed. Zone Light Meter calculates this automatically once you tell it your bellows extension.