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

Angular resolution — where it appears

How finely a picture samples the directions it holds, counted as marks per square degree of world rather than per unit of page. It varies across a single picture surface by up to a factor of twenty-five, and a reprojection can move it but never increase it.

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

plane — ×24.99 edge to centrecylinder — ×2.40 edge to centrestereographic — ×2.22 edge to centreequidistant — ×1.30 edge to centreequal-area — ×1.00 edge to centreequirect. — ×1.34 edge to centre36 cells of 377 square degrees, out to 70°equal-area ×1.00 · plane ×25.0

Where a surface spends its pixels

A picture surface is a budget before it is anything else, and the six named ones distribute the same marks over the same directions quite differently. The flat plane lays 25.0 times as many on a square degree at the edge of a 70° field as on one at the centre; the equal-area fisheye is flat to 8.3e-6 per cent.

curved · Resolution 02401020304050degrees off the optical axis, inside the reprojected framemarks the target wants, per mark the source laid downone mark for one mark×5.49 at the edge68% of the source unusedcorrect from 6.7 cm at 160 mm wide

Shot on one surface, shown on another

Two picture surfaces are two charts of the same pencil of rays, so a reprojection between them is a change of coordinates and loses no geometry at all — bit-exact at all 408 sampled directions. What it costs lies elsewhere — 70 per cent of the source has nowhere to go, and the target wants ×5.49 the marks at its edge.

curved · Composite

Named alongside it

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

Area scaleEquidistantfield of viewFisheyePicture surfaceSolid anglecentre of projectionChartEqual-areaEquirectangularre-projectionStereographic

All concepts