Cinématographe

Period film stock was cellulose nitrate: it self-ignites, burns without outside oxygen and caused many cinema fires. Work only on acetate or polyester base.

Title: “Apparatus for obtaining and viewing chronophotographic proofs”. One apparatus to take the pictures AND to see them — it is all in the title.

Slide a strip of images past a window without stopping: all you see is a blur. Each frame has to be still while you look at it.

Machine a channel that guides the film perfectly flat behind a rectangular window. Film that buckles gives an image blurred along one edge only.

Perforation pitch sets frame height. An irregularity of a few tenths makes the picture jump vertically on projection.

Cut two fine points mounted on a moving carrier. They must enter the perforation without tearing it and withdraw cleanly.

The claw must follow four movements: in, down, out, up. This is the motion of a sewing machine needle feed, and the Lumières took it directly.

Measure the claw's travel. Too short and the picture creeps up; too long and it creeps down. The setting must be exact, not close.

Fit a disc with an opaque sector, timed to mask the window while the film moves. Without it you see the film sliding between frames.

Both must run from the same axle. Approximate synchronisation gives either a light veil or an image smeared vertically.

Allow a loop of slack each side of the gate. It absorbs the jerk: without loops the film tears at the perforations within seconds.

Count two turns per second for eight frames per turn. That was the Lumière rate; 24 frames per second only arrives with sound.

Replace the taking lens with a lamphouse and a projection lens. The transport mechanism stays the same — that is the governing idea of the apparatus.

At sixteen frames per second the image flickers. Add extra blades to the shutter so the light is cut two or three times per frame: the frame rate is unchanged and the flicker disappears.

The patent. Auguste and Louis Lumière filed French patent no. 245,032 on 13 February 1895, “Apparatus for obtaining and viewing chronophotographic proofs”. Louis Lumière designed the mechanism with the engineer Charles Moisson, and Jules Carpentier manufactured it. The first paying public projection took place on 28 December 1895 at the Salon Indien of the Grand Café, boulevard des Capucines in Paris.

An apparatus against a machine. Edison's earlier Kinetoscope worked perfectly well but could only be watched through a peephole, one person at a time, on a heavy mains-powered machine. The Cinématographe weighs about five kilos, runs on a crank, and serves in turn as camera, printer and projector. That portability explains the spread: Lumière operators went out to film and project in Russia, Egypt, Japan and South America, and brought back views of the whole world in under two years. The advantage was not optical, it was logistical.

The claw comes from sewing. The central problem of any cinema apparatus is contradictory: the film must advance and stand still during exposure. The Lumière solution is a claw mechanism derived from the cloth feed of a sewing machine — two points trace a rectangle, pierce the perforation, pull the film down one frame, disengage and rise. During the still period the shutter opens; during the movement it closes. The slack loops on either side absorb the jerk, without which the film tears at the perforations.

On persistence of vision. Cinema is often explained by “persistence of vision”. This is inaccurate: the after-image exists but does not explain perceived motion. Psychologists now attribute the illusion to the phi phenomenon and beta movement — that is, to processing in the brain rather than the eye. At sixteen frames per second motion reads but the image flickers; so shutter blades were multiplied to interrupt the light two or three times per frame. That raises the flicker frequency without raising the frame rate — an engineer's trick that treats the eye and the perception as two separate problems.