Visual Plane
every picture states the point it is correct from
Concept

Telephoto compression — where it appears

The flattened look of a long-lens picture, which is a consequence of where the camera stood rather than of the lens. Moving the camera is what changes the near-to-far ratio; changing the focal length changes the framing and leaves that ratio exactly where it was.

Named by 3 essays across 2 fields — each of them below, with the objects they name alongside it.

3 m, 50 mm1.50 m, 25 mmsubject ×1.000000 · background ×0.526 · zoom alone would give ×1 for bothnear-to-far ratio 10.00 → 19.00changing the focal length leaves it at 1.000000000000

Stepping closer is not zooming

Changing the focal length leaves the ratio between any two things in a picture exactly alone — to twelve decimal places, at every focal length there is. Moving changes it. Hold the subject's drawn size across a step from 3 m to 1.5 m and the background halves, which is the whole of the shot everybody knows and nobody derives.

sensor · Dollyzoom halfway along the drawn linethe actual midpointcorrect from 26 cm, at 160 mm wide7 px apart

The eye taken to infinity

A parallel projection is a photograph from infinitely far away with the lens lengthened to match. That is not an analogy — it is the limit, it can be watched happening, and it explains why a long lens flattens a scene and why an isometric drawing has no viewing distance to state.

parallel · Limit principal pointoutward nearer than 5 m · still at 5 m · inward beyond5 points on the held plane do not move

A dolly zoom is a step and a zoom, and they meet at one depth

Step 1.5 m toward a subject 5 m away while shortening the lens to hold its size. Every mark moves along the line from the centre of the picture, to a ten-trillionth of a degree — outward if nearer than the subject, inward toward a limit if further, and not at all on the subject's own plane. The step and the zoom each move everything one way; the dolly zoom is where they cancel.

sensor · Dollyzoom

Named alongside it

The objects these essays reach for when they reach for this one.

Depth cueDiminutionfield of viewFocal lengthStation pointViewing distanceCrop factorDemonstrationDepth compressionForeshorteningIsometricOrthographic

All concepts