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

braccio — where it appears

The Florentine arm's length, the unit a fifteenth-century pavement is laid out in and the unit Alberti's construction divides its ground line into. It is a length in the world; the picture records only the ratio of it to the panel's viewing distance, which is why a pavement never states a size.

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

the panelhorizon — the centric point's heightthe section — the eye, the panel, the ground470 px — the viewing distancethree routes agree to 6e-14 pxsection, distance point, and a pinhole camera

Alberti draws a pavement, and chooses where the reader stands

The costruzione legittima of 1435 is exact. Run as a construction — with drawn rays and drawn intersections rather than the formula it turns out to satisfy — it agrees with a pinhole camera to six parts in a hundred trillion of a pixel. And it has one free parameter that the recipe never names, which is the distance from the eye to the panel.

construction · Alberti the distance pointAlberti's sectionthe measuring pointcorrect from 12 cm at 160 mm widethree routes, 0e+0 px apart

Three procedures, one panel

Alberti's lateral section, the distance-point construction and a pinhole camera put every transversal at the same pixel — and every reading of the finished drawing therefore returns the same number for all three. The methods are distinguishable on the desk and indistinguishable on the panel, which is the fact any attribution has to start from.

construction · Attribution

Named alongside it

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

costruzione legittimaTransversalViewing distanceAttributionCentric pointCross-ratioDistance pointFocal lengthGround lineHorizonLateral sectionMeasuring point

All concepts