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

Degeneracy — where it appears

A configuration in which the quantity being sought has left no trace in the data, so no method whatever can recover it.

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

-10-50-2-10baseline (m, log scale)worst deviation in the recovered shape (log scale)exact pointsread to 1 pxat 2 mm: 4.7e-9 exact, 2.9e+1 read to 1 px6e+9× apart

A turn of the head is not a step sideways

The textbook says a short baseline makes reconstruction ill-conditioned. Measured, the algebra does not notice — a two-millimetre baseline recovers the courtyard to nine digits from exact marks. What fails is the ratio of baseline to reading error, and it fails without refusing.

depth · baseline pixels 2.00 : 1recovered focal length219.9 pxthe camera's actual one436.4 pxwhat the recovery returnsspread across three estimates 0.0e+0worst bundle residual 9.1e-13 pxboth are what a wrong picture would trippixel aspect 2.00 unmodelledfocal length 49.6% short, every diagnostic clean

The pixel that is not square

A camera with two focal lengths is a real thing — anamorphic cinema optics, non-square photosites, a stretched video format. Hand this site's own round trip a picture from one and it returns a focal length 49.6% out, a principal point far from the truth, three independent estimates agreeing to 1e-16, and bundle residuals at the noise floor. Every alarm the site has stays silent.

sensor · pixelaspect

Named alongside it

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

ResidualAnisotropyAspect ratioBaselineCamera calibrationCamera matrixConditioningDemonstrationEntrance pupilEpipoleFocal lengthHomography

All concepts