Crop factor is the ratio of the full-frame sensor diagonal (43.27mm) to your sensor diagonal. APS-C sensors have crop factors of 1.5x (Nikon/Sony) or 1.6x (Canon). It determines how much the field of view is narrowed compared to full frame. A 50mm lens on a 1.5x crop sensor gives the same field of view as a 75mm lens on full frame.

Does crop factor change the actual focal length?

No. A 50mm lens is always 50mm regardless of sensor size. Crop factor only affects the field of view — the sensor captures a smaller portion of the image circle. The focal length, aperture, optical quality and perspective remain the same. Only the framing changes.

What is equivalent aperture?

When comparing depth of field between sensor sizes, you multiply the aperture by the crop factor. A 50mm f/1.8 on APS-C (1.5×) gives similar depth of field to 75mm f/2.7 on full frame (1.8 × 1.5 = 2.7). This does NOT affect exposure — f/1.8 lets in the same amount of light per unit area on any sensor, so shutter speed and ISO are unchanged.

Does medium format have a crop factor below 1?

Yes. Medium format sensors are larger than full frame, so their crop factor is less than 1. The Fuji GFX system has a crop factor of about 0.79x. A 63mm lens on GFX gives the same FOV as a 50mm on full frame, but with shallower depth of field.

Crop Factor Calculator — Equivalent Focal Length & Aperture

Convert focal lengths between sensor sizes and calculate equivalent aperture for depth of field comparison.

Focal Length

The focal length marked on the lens (e.g. 50mm). This stays the same on any camera body.

Aperture

The f-number you're shooting at (e.g. 1.8). Used to work out the equivalent aperture for depth-of-field comparison.

Sensor / Crop FactorPick your camera's sensor format, or choose 'Custom crop factor' to enter your own

How We Calculate This

Crop factor converts between sensor sizes for equivalent framing:

Equivalent Focal Length

Equivalent FL = actual focal length × crop factor

A 50mm lens on an APS-C (1.5×) body frames like a 75mm lens on full frame.

Equivalent Aperture (DOF)

Equivalent aperture = actual aperture × crop factor

This applies to depth of field only — it does not change exposure. f/1.8 stays f/1.8 for brightness on any sensor.

Field of View

FOV = 2 × arctan(sensor dimension ÷ (2 × focal length))

Full-frame reference dimensions are 36mm wide × 24mm high (43.27mm diagonal); the crop-sensor dimension is the full-frame value ÷ crop factor.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard optical and photographic formulas. Results may vary with specific equipment.