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
Polaroid SX-70 cost of $180 for the camera and $6.90 for each film pack of ten pictures ($ and $, respectively, adjusted for inflation) limited demand, Polaroid sold 700,000 by mid-1974. In 1973–4, the Skylab 3 and 4 astronauts used an SX-70 to photograph a video display screen to be able to compare the Sun's features from one orbit to the next. There were a variety of models beginning in 1972 with the original SX-70, though all shared the same basic design. The first model had a plain focusing screen (the user was expected to be able to see the difference between