Polaroid (polarizer) Polaroid (polarizer) Polaroid is a type of synthetic plastic sheet which is used as a polarizer or polarizing filter. A trademark of the Polaroid Corporation, the term has since entered common use. The original material, patented in 1929 and further developed in 1932 by Edwin H. Land, consists of many microscopic crystals of iodoquinine sulphate (herapathite) embedded in a transparent nitrocellulose polymer film. The needle-like crystals are aligned during manufacture of the film by stretching or by applying electric or magnetic fields. With the crystals aligned, the sheet is dichroic: it tends to absorb light which is polarized parallel to
History of the single-lens reflex camera a modular camera, in which various assemblies such as the pentaprisms, the focusing screens, the special 35mm roll film 250 exposure film back and the Speed Magny film backs (two models: one using the Polaroid 100 (now 600) type pack films; and another Speed Magny was designed for 4×5 film accessories, including Polaroid's own 4×5 instant film back). These could be fitted and removed, allowing the camera to adapt to almost any particular task. It was the first 35 mm camera offered with a successful motor drive system. Unlike most of the other manufacturers involved in 35mm camera production, the