ImageReasonFocus, Depth of Field, and Macro
How much depth do I actually have at this magnification?
Enter your magnification, marked aperture, and circle-of-confusion criterion to see the approximate macro depth of field and effective f-number together.
Answer
Want to learn more? Circle of Confusion and Depth of Field
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Calculate to see the focus slab against subject depth.
| Aperture | DOF | Effective f-number |
|---|
Calculate a result to generate a copyable plan.
Depth shrinks fast at close magnification
At close magnification, depth of field can become dramatically smaller than the distance scale suggests. The marked aperture is not the whole exposure and depth story either: bellows-style magnification raises the effective f-number. This planner keeps both results together, so a decision about aperture also exposes the likely need for light or a focus sequence.
At one-times magnification, f/8, and a .015mm circle-of-confusion criterion, the approximate total depth is .48mm and the effective f-number is f/16. Doubling magnification to 2× cuts the depth to about .18mm while moving the effective f-number toward f/24. If the critical subject depth is 2mm, one frame may not cover it. Start with a test frame, then use a planned overlapping sequence rather than assuming a stack will repair movement.
This result models the values you entered. It cannot see the scene, verify focus or movement, predict camera-specific processing, or guarantee the final photograph. Use it as a stated starting point, then check the important subject area in a test frame or proof.
Make one controlled test with the important variable held constant. Inspect the subject detail, motion, highlights, and intended output, then adjust the setting that protects the priority you named.
FAQ
- Why does effective aperture get darker at macro distances?
- Image magnification increases the effective f-number. The displayed value is a planning relationship, not a transmission measurement.
- Why no universal best setting?
- There is no universal best setting because the relevant tradeoff changes with the subject, light, movement, output, and the part of the image that matters. This tool makes the stated tradeoff visible rather than hiding it behind a generic recommendation.