Bellows Extension Calculator

Calculate exposure compensation and magnification for bellows macro photography.

Bellows & Lens Settings

Lens Focal Length (mm)

Bellows Extension / Total Extension (mm)

Total distance from film/sensor plane to lens optical center

Lens Aperture (f/)

Base Shutter Speed (metered without bellows)

1.0:1

1.00x life size

Bellows Factorx4.00

Exposure Compensation+2.0 stops

Effective Aperturef/16.0

Base Shutter1/60

Compensated Shutter1/15

Working Distance100.0mm

Depth of Field0.96mm

Subject Coverage36.0mm x 24.0mm

Extension for 1:1100mm

For 1:1 magnification, extension equals 2x focal length

• Use a sturdy tripod - vibration is magnified at high magnification

• Focus by moving the camera/subject, not the lens

• Stop down for more DOF but watch for diffraction

• Consider focus stacking for greater depth of field

• Use mirror lock-up or electronic shutter

• Flash lighting helps freeze subject movement

Magnification = (Extension - FL) / FL

Bellows Factor = (1 + M)²

Exposure Comp = log₂(Bellows Factor)

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MyCalcBuddy Editorial Team

This page is maintained as an educational calculator reference.

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Formula Source: Standard Mathematical References

by Various

ðŸ”„Last reviewed: May 2026

âœ“Formula checks are based on standard references and internal QA review.