Crop Factor Calculator

Translate focal length and optional aperture equivalence across sensor formats. Perfect for understanding how your lenses perform on different cameras.

Equivalent focal length
DoF-equivalent aperture
Assumptions

Equivalent focal length matches field of view: focal × (target crop ÷ source crop). Aperture equivalence is for depth-of-field comparison only.

Worked Example

Scenario: Comparing 50mm f/1.8 on full frame vs Micro 4/3

Setup: Source: Full frame (1.0) → Target: Micro 4/3 (2.0)

Equivalent focal length: 50mm × (2.0 ÷ 1.0) = 100mm

DoF-equivalent aperture: f/1.8 × (2.0 ÷ 1.0) = f/3.6

Meaning: Your 50mm f/1.8 on full frame looks and feels like a 100mm f/3.6 on Micro 4/3

Understanding the Results

Focal Length:
Affects field of view and magnification. Higher crop factors make lenses appear more telephoto.
Aperture DoF:
For depth of field comparison only. The actual f-stop for exposure remains unchanged on your lens.
Exposure:
f/1.8 always gathers the same amount of light regardless of sensor size—only DoF appearance changes.

FAQ

What is crop factor?

The ratio of diagonal measurement between a full frame sensor and your camera's sensor. Smaller sensors have higher crop factors.

Why does my lens look more telephoto on crop sensors?

Smaller sensors capture a narrower portion of the image circle, effectively cropping the image and making it appear more zoomed in.

Does crop factor affect exposure?

No! f/2.8 is f/2.8 regardless of sensor size. Only depth of field appearance changes.

When should I use aperture equivalence?

When comparing depth of field between different sensor formats, or planning a look you want to recreate on different gear.

Do I need to multiply my focal length?

For lens selection purposes, yes. If you want "50mm full frame look" on APS-C, use a 35mm lens (50 ÷ 1.5).

What about ISO equivalence?

Larger sensors typically perform better at high ISOs due to larger pixel sizes, but this tool focuses on focal length and DoF.

Related Tools

Field of View Calculator · Hyperfocal Distance · Equivalent Exposure

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