Why do I need equivalent focal lengths?

When switching between camera systems with different sensor sizes, equivalent focal lengths tell you which lens on the new system gives the same field of view. For example, switching from APS-C to full frame, a 35mm APS-C lens is equivalent to about 23mm on full frame — you would need a 23mm FF lens for the same framing.

How do I convert between any two sensor sizes?

First convert to full frame equivalent (multiply by the source crop factor), then divide by the target crop factor. For APS-C (1.5x) to MFT (2x): multiply by 1.5, then divide by 2. A 50mm APS-C lens is equivalent to 37.5mm on MFT.

Does equivalent focal length affect perspective?

Equivalent focal lengths give the same field of view, but perspective depends only on camera-to-subject distance. If you stand in the same position, you get the same perspective regardless of focal length — cropping simply selects a portion of the scene. Moving closer or further changes perspective.

What full-frame focal lengths are most common?

Key focal lengths on full frame: 14-16mm ultra-wide landscape, 24mm wide reportage, 35mm street, 50mm standard/portraits, 85mm portrait, 135mm tight portrait/events, 200-400mm wildlife/sport. On APS-C, divide by 1.5 for the equivalent lens: 35mm FF ≈ 23mm APS-C.

Equivalent Focal Length Calculator — Cross-System Comparison

Find the equivalent focal length when switching between sensor sizes to maintain the same field of view.

Focal Length

Lens focal length

Source Sensor

Camera you have

Target Sensor

Camera you want to match

How We Calculate This

This calculator converts focal lengths between any two sensor sizes:

Conversion Formula

FF equivalent = focal length x source crop factor

Target FL = FF equivalent / target crop factor

This works because crop factor represents the ratio of full-frame diagonal to sensor diagonal. The field of view is determined by the ratio of sensor size to focal length, so matching FOV requires scaling the focal length by the ratio of crop factors.

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.