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Crop Factor and Equivalent Lens Settings

Equivalent focal length and depth-of-field aperture from a nominal sensor crop factor.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Formula and method

The worked inputs demonstrate the selected model; change a known value or leave an editable unknown empty for a supported inverse.

Equivalent focal length = focal length × crop factor × converter

Worked example

Enter these known values and leave the other values blank.

Lens focal length
50 mm
Aperture f-stop value
4
Focal reducer/teleconverter
1 ×
Lens focal length
50 mm
Aperture f-stop value
4

Assumptions and limitations

  • Presets are illustrative nominal sensor dimensions. Their crop factors are computed from diagonal ratios against 36 × 24 mm; they do not certify measurements or labels of a specific camera model.
  • Equivalent aperture describes comparable depth of field and total-light framing, not a change to the lens exposure f-number.

Common questions

What does this model assume?

Sensor presets are nominal rounded crop factors, not guaranteed model-specific measurements. Their stated dimensions permit a diagonal-ratio check against 36 × 24 mm. Equivalent aperture describes comparable depth of field and total-light framing, not a change to the lens exposure f-number.

How do units and inverse calculations work?

Choose compatible units for each quantity. The model converts quantities internally; supported editable fields can be solved from sufficient independent known values. Display rounding does not change the underlying value.

References

Explicit model domains enforce physical bounds and strict whole-count membership where required. Explanatory image content is replaced by original dimension descriptions without changing its visibility. Crop presets are computed from their explicitly stated nominal sensor dimensions using the diagonal ratio to a 36×24 mm reference. This corrects inconsistent rounded captured ratios and labels the dimensions as illustrative geometry rather than validated camera-format specifications. Every conditional diagram follows the corrected ratio.

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