Invisible Center

Every photograph that claims to measure the world rests on three numbers nobody ever looks at: a distance, f, and a point, (cx, cy). No datasheet gives them. Without them, an image is only an image.

Invisible Center is a workshop, not a measuring instrument. Three chapters, all of them worked with your finger.

The chamber. A camera reduced to what matters: a point, a plane, a distance. Turn it to see where the principal point actually sits. We imagine it at the centre. It almost never is.

A few pixels. Shift cx and cy by a few pixels and watch what becomes of the measurement. A tiny flaw, an error that is not.

Finding the camera. Six sightings on a known building, nine unknowns, and a calibration that walks instead of leaping. You start the computation and follow its iterations and residuals until they settle.

It is also a reflection on a reversal: metric chambers declared their geometry by construction, you could see their tie rods. Our cameras are optically admirable and metrologically mute.

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An IMAGE4D application.