What is lens compression?

Lens compression (more accurately, perspective compression) makes the background appear larger and closer to the subject. It is caused by camera-to-subject distance, not focal length. When you use a telephoto lens, you stand further away — this distance creates the compression effect. Cropping a wide-angle shot from the same position gives identical compression.

Does focal length cause compression?

No — distance does. Focal length only determines magnification (how much of the scene you capture). Two photos taken from the same distance with different focal lengths show identical perspective when the wider one is cropped. The compression changes only when you move the camera.

How do I use compression creatively?

Use compression to make backgrounds appear closer (telephoto from far away) — great for bringing mountains behind a subject. Use wide-angle close up to exaggerate distance and depth. Portrait photographers use moderate compression (85-135mm on FF) for flattering facial proportions.

Why do wide-angle lenses distort faces?

When you photograph a face up close with a wide-angle lens, the nose is much closer to the camera than the ears. This distance difference is exaggerated, making the nose appear larger. At telephoto distances, the nose-to-ear distance is tiny relative to camera-to-subject distance, so proportions look natural.

Lens Compression Calculator — Perspective Compression

Visualise how perspective compression changes the apparent relationship between subject and background at different distances.

Subject Distance

Camera-to-subject distance. Moving the camera back increases compression.

Background Distance

Camera-to-background distance (must be greater than the subject distance).

Subject Height

Subject size measured along one axis — e.g. a person's height (~1.8 m).

Background Height

Background feature size measured along the SAME axis as the subject (both heights or both widths).

How We Calculate This

Perspective compression depends entirely on where the camera stands, not on the lens. The calculator works it out from the distances and sizes you enter:

Angular Size

Angular size = 2 × arctan(height ÷ (2 × distance))

This gives the angle each object subtends at the camera. We measure the subject and the background along the same axis (both heights or both widths), then take the ratio.

Apparent Background Size

Apparent size = (background angular size ÷ subject angular size) × 100%

A value above 100% means the background looms larger than the subject — the hallmark of strong compression. Compression gets stronger as the camera moves farther from the subject: the gap between subject and background then becomes proportionally smaller (a smaller background-to-subject distance ratio), so both render at a more similar size and the background appears to crowd in behind the subject.

Distance Ratio

Ratio = background distance ÷ subject distance

This describes the geometry only. Counter-intuitively, a smaller ratio (camera far back) gives stronger compression, while a large ratio (camera close, subject just in front of a distant background) gives a wide-angle look with the background pushed away.

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.