Macro exposure compensation
Close focusing loses light. Find the extra stops from magnification.
Matters mostly on bellows / large format and true macro. TTL metering already accounts for it.
About this tool
When you focus close, the lens moves farther from the film and less light reaches it, so a meter reading underexposes. Enter the focal length and the actual bellows extension, and this tool returns the extra stops of exposure the close-up demands. It keeps macro and large-format close focusing correctly exposed.
How to use it
- Enter the lens focal length in millimetres.
- Enter the bellows extension, the distance from the lens to the film plane.
- Read the compensation in stops and add that much exposure.
FAQ
When can I ignore bellows compensation?
At normal distances the extension roughly equals the focal length and the correction is negligible. It only becomes significant in close-up and macro work, growing large near and beyond 1:1 magnification.
Does this apply to my 35mm SLR?
The physics is the same, but many modern SLRs meter through the lens and already account for the light loss. The calculator is most useful with hand-held meters, bellows units and view cameras.