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
Folding camera the Polaroid SX-70 Instant film camera, and the Speed Graphic press cameras used folding designs into the 1970s. The typical amateur camera of the early 20th Century made various "postcard" sized negatives around 4" × 5". By the 1930s 6cm × 9cm cameras for either the 120 or 620 film size, were highly popular. The use of folding cameras declined in the late 1930s with advances in lens technology allowing superior enlargement, high quality images on smaller negatives, and shorter distances between the lens and the film. 35mm film made small-sized cameras practical without using bellows. Lens technology allowed 120/620