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 type 55 Polaroid type 55 Polaroid Type 55 film is a black-and-white peel-apart Polaroid film that yields both a positive print and a negative image that can be used to create enlargements. The film speed is given by the manufacturers as 50 ISO, however that applies only to the positive component. The negative is rated by Polaroid as 25 ISO though it is possible to rate the negative at 32 ISO). After processing the film is peeled apart to reveal positive and negative images. To prevent fading and physical damage the positive image requires a protective coating (included in the box) while