Light Tracing

Definition

Light tracing names the documentation technique — and the representational idea behind it — in which a point of light stands in for the moving body, its path registered as a visible trace. Weinthal's chapter supplies two canonical instances and one ancestor. The ancestor: in Woolf's Orlando, a servant's movement through the palatial residence "was made visible by the main character… from one interior into another" by "a single point of light illuminated by an oil lantern or candle" — "the characters' movements mapped by their direct connection to light." The theatrical instance: at Anna Pavlova's cancelled 1931 The Hague performance (she died the night before), "the performance went on but rather than being danced by Pavlova, she was represented by a point of light moving across the stage to mark her movements. The point of light was a projection that registered on the floor, similar to an orthographic plan view marking one-dimensional points, and similar to the pirouette discussed earlier." The laboratory instance: Callaghan and Palmer's "dark technique" photograph, in which the actor wore "lights attached to head, hands, elbows, feet, and back… The shutter of the camera was left open throughout the action and the moving lights recorded the paths of motion" — "a time-lapse capturing movement made by the tracings of a point of light."

The concept's theoretical claim is that light is the moving body's admissible substitute within a drawing system that refuses bodies: "Since this system is not conducive to the recording of a person, perhaps light as a replacement for the body can be considered an intermediate step toward an alternative iteration of the drawing. After all, the same rules and variables apply." The light-point obeys the orthographic variables (a point, registered on a plane, at true location) while carrying the temporal information the system excludes. Callaghan and Palmer's version had the double virtue Weinthal prizes — "true data was extracted, while simultaneously fulfilling a phenomenal graphic" — and their whole collection of experiments "could be seen as the precursors to current motion capture technology." The chapter's frame thesis names the technique's captivation: "the fleeting can always be grounded in true data, and the means by which the fleeting is documented can be captivating due to the invisible forces that are being made visible."

Key Thinkers

• (Named in the source, not yet paged — see log: Jane Callaghan & Catherine Palmer — inventors of the "dark technique" photograph, the light-point time-lapse of bodies in domestic action.)
• (Named in the source, not yet paged — see log: Anna Pavlova — the dancer whose cancelled final performance survived as a stage-light traversing the floor, the technique's most poignant realization.)
• (Named in the source, not yet paged — see log: Virginia Woolf — the Elizabethan lantern-and-candle world of Orlando, where light-borne movement is visible "from one interior into another.")
• Lois Weinthal — the concept's theorist: light as "a replacement for the body," the "intermediate step" by which the temporal enters the orthographic variables.

Related Concepts

• Orthographic Projection — the system the light tracing satisfies: the point of light is "similar to an orthographic plan view marking one-dimensional points" — the body's dynamic truth smuggled in through the system's own variables.
• Space-Shape — the sibling technique from the same laboratory: where the space-shape interpolates the movement's volume, the light tracing records its path — trajectory against sweep.
• Indexicality — the semiotic register: the light tracing is the index par excellence, a mark physically caused by the movement it signifies — smoke-of-fire, footprint-of-walker in photographic form; "true data" and Peirce's existential connection in one exposure.
• Temporality — the technique's payload: the open shutter accumulates time into a single image, the movement's duration made simultaneously visible — the time-slice problem answered by superimposition.
• Representation — the standing question: is the light tracing a representation of the body or of its absence? The trace remains when the dancer (Pavlova) is gone — representation of movement by the body's evacuated surrogate.
• Movement Perception — the documentary counterpart: chronophotography (Marey, Muybridge) registered "change… over a sequence of still frames"; the light tracing compresses the sequence into one frame.
• The Visible and the Invisible — the technique's affect: "the means by which the fleeting is documented can be captivating due to the invisible forces that are being made visible" — invisibility (movement, time, labour) converted into visible line.

Source Support

Sources in the wiki that discuss this concept:

• A pirouette on the orthographic hinge (Weinthal 2018) — the concept's source: Woolf's carried lights, Pavlova's stage-point, Callaghan & Palmer's "dark technique" photographs (lights "attached to head, hands, elbows, feet, and back"; the open shutter; "the moving lights recorded the paths of motion"), and the motion-capture lineage claim.

Open Questions

• Pavlova's light-point was at once memorial and documentation — the dancer's path performed by her surrogate. Is the light tracing a representation of the body, or the body's absence made drawable — and does the difference matter for a discipline that designs for bodies?
• The "dark technique" photograph needs darkness: the trace is legible only when the world is excluded and the light-point isolated. Does the technique's legibility depend on the same erasure of context ("clean and objective") that Weinthal diagnoses in orthographic drawing itself?
• Callaghan & Palmer attached lights to "head, hands, elbows, feet, and back" — multiple simultaneous points. One point yields a path; many yield a choreography. Is there a scale at which light tracings stop being documentation and become the thing designed — the interior as the field its occupants' traces compose?
• Weinthal calls light "an intermediate step toward an alternative iteration of the drawing." What is the final step — movement-rules in construction documents, real-time sensor interiors (Taylor's responsive environment), or a drawing convention not yet invented?