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

Roughness — where it appears

How large a residual's second differences are against its own size, which separates the ways a hand or a rule enters a drawing. Independent errors give the square root of six exactly; a walk gives less because its neighbours are correlated, and a smooth rule gives least of all.

Named by 4 essays across 2 fields — each of them below, with the objects they name alongside it.

the distance pointone mark on the horizonleaves another exact drawingAlberti's sectionone mark per braccio, each from the panelleaves errors each its ownthe measuring pointdividers walked along the measuring lineleaves errors that accumulatea photographnoneleaves a smooth curvethe constant ratioone ratio, applied throughoutleaves a smooth curveone hand step eachand four kinds of trace

One hand step each

Every classical perspective construction has exactly one step a person performs by hand, and the four constructions perform four different steps. That single difference decides everything a finished drawing can say about its maker, because the answers are identical and only the mistakes are not.

construction · Handerror 0.4000.6000.80011.201.40braccia in the pavement (log₁₀)the worst departure of a mark, in pixels (log₁₀)steppedmeasured from the zerothe same hand, laid off two ways√n against n^0.21

Stepped, or measured from the zero

The same hand at the same precision, laying the same braccia off two ways — dividers walked from the last mark accumulate and grow as the square root of the count, while marks set from a common origin do not accumulate at all. The difference is not which method was used — it is where the zero is, and only the second is recorded in the drawing.

construction · Handerror wrong hzcorrectno shapefrom a zerosteppeda rulethe distance pointAlberti's sectionthe measuring pointa photographthe constant ratio60144157203036060read with the panel's own horizon60 drawings each

What a panel says about its maker

The reading assembled over this row, run against every procedure sixty times and scored — with the failures reported as carefully as the successes, because three of the five rows are refusals. A drawing names the class of error in it, not the recipe that produced it, and one procedure it never names at all.

construction · Attribution the constant-ratio rulecorners off the chord by 8.03 pxAlberti's sectioncorners off the chord by 2.47 px

A straightedge convicts the rule on five braccia

The constant-ratio rule for spacing a pavement's boards leaves one mark a correct construction does not: its tile corners bow off the diagonal. The worry was that a painter's hand would bury the bow in its own scatter. At a pixel of scatter it does not, on any pavement of five braccia or more. What limits the test is not the hand but the page: a pavement drawn to one width bows no more at twenty braccia than at eight, while the hand's wander keeps growing with every tile.

wrong · Taughtratio

Named alongside it

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

AttributionError termProcedureResidualFalsifiabilityIdentifiabilityMeasuring pointrandom walkTransversalAsymptoticsbraccioConfusion matrix

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