ClarityHow to use this tool
- Enter total lens-to-image distance, focal length.
- Select Calculate to view the result.
- Check the method and assumptions below before using the result.
The method, explained
Exposure factor=(extension/focal length)²; compensation stops=2log2(extension/focal length).
Using total lens-to-image distance = 100 mm, focal length = 50 mm, the result is 2 stops. Change these example inputs to match your task; use the method above to check each step.
Understanding your result
Symmetric thin-lens approximation. Enter total extension, not only extension-tube length. Internal focusing and pupil magnification can change compensation.
What to keep in mind
Symmetric thin-lens approximation. Enter total extension, not only extension-tube length. Internal focusing and pupil magnification can change compensation. An ideal geometric or exposure estimate. Lens behavior, stabilization, sensor crop and scene conditions may change practical results.
Common questions
How do I use this bellows exposure compensation calculator?
Estimate macro exposure compensation from lens-to-image extension and focal length. Enter total lens-to-image distance in mm, focal length in mm. The starting example is editable; use values for the same system or project.
Which assumptions affect this result?
Symmetric thin-lens approximation. Enter total extension, not only extension-tube length. Internal focusing and pupil magnification can change compensation.
Methodology maintained by ClarityKit. How these tools are built and checked.