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photography to secure them; (3) the use of a single camera; (4) of perforated film; (5) of intermittent film movement; and (6) in making the period of illumination exceed the period of change or substitution of a new picture element, or frame, for the last in sequence throughout the series.
The first motion picture mechanism we have any record of is the zoetrope, or wheel of life, though its origin is buried in antiquity. It may be that this is the device Lucretus was writing about.
It usually consists, as you all doubtless well know, of a paper cylinder having equi-spaced axial slits cut through its wall. Between the slits on the inside were arranged sketches of successive phases of an object in motion. By whirling the cylinder and viewing the sketches through the slits as they The Zoetrope passcd the cyc ouc got the sensation of an object in motion.
The picture series were also put upon a slotted disc (this form may have antidated the drum type) and were viewed by looking through the slots at the reflection of the pictures in a mirror as the disc was whirled.
The first attempt at projection followed this line, that is, transparencies were mounted in disc form and illuminated from the back, a projection lens imaging these on a screen as the successive pictures of the series were momentarily exposed in the field of the lens.
Plateau, who seems first to have made up such a mechanism, mounted sixteen pictures on his disc, suitably illuminated them through a whirling opaque shutter having a single radial slot therein, the shutter disc rotating sixteen times as fast as the picture disc. Though blind. Plateau appears to have given diligent study to this persistence of vision phenomena, and at this early date, 1849, curiously enough, hit upon the same picture frequency now universally used. This picture disc, intermittently illuminated, was subsequently employed by several experimenters.
Another form was exactly the reverse of this plan, for instead of a single stationary lens and stationary light with a 16-picture transparent disc revolving between, consisted of a stationary disc with 16 pictures and 16 lenses, a single lens mounted in front of each picture, while the light whirled around to momentarily pass through each picture and adjacent lens. As all the lenses were adjusted to register at a single spot on the screen, the composite on the screen appeared, by persistence of vision, as a single uninterrupted picture.
The idea of simulating motion by intermittent illumination of a series of related picture elements seems to have been the preferred method for more than a hundred years, the last of the line being Edison's Kinetoscope of 1894 (to be described later).
The picture series were first made in a camera in 1860, to the best of my knowledge, by Colman Sellers, an engineer, who, in one form, pasted the photo prints on an endless band for exhibition.^
^Sellers, U. S. Patent No. 31,357, issued Feb. 5, 1861.
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