Clear Film: Inexpensive polyethylene film, which is '. for temporary greenhouses, has a useful of only six months, and a vinyl film (polr. chloride) lasts about one year. Mylar p ester is a tough clear film with a life expect: of several years. Rigid plastic, either finer : or polyvinyl chloride, is relatively perma: Plastic-covered greenhouses are tighter . glass houses and require less fuel for heat. t> a second layer of plastic is placed inside lie greenhouse framework, a fuel saving of appron mately 40% can be achieved. However, plastics used in greenhouses are combustible and are often not transparent.
Speedlights flash, the picture is taken, the film automatically advances, the shutter is cocked, and all is in readiness for the next child in the line. Similar cameras are available which operate with 35mm film. The smaller film cuts costs a bit but naturally the contact prints are not so appealing as those from the larger film.
The original Kodak was a box camera, 3:/4 x 3% x k inches with a fixed-focus lens of 27mm focal length d aperture f/9, fitted with an ingenious cylindrical, or rrel, shutter. It differed from most of its competitors cause it used film in a roll long enough for 100 nega-res, each with a circular image 2l/2 inches in diameter. : first this "American Film" was paper, coated with a bstratum of plain gelatin and then with light-sensitive latin emulsion; after processing, the hardened gelatin aring the image was stripped from the paper base. This licate operation became obsolete with the introduction "transparent film" on a clear plastic base of nitrocel-ose in 1891.
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Photography
