Microform polarity

A microform is any photographic storage medium that requires magnification to be read by the human eye. Examples include microfilm, microfiche and photographic film. Microforms can have positive or negative polarity. In positive polarity microforms, the colours and tones of the image will be
represented as they appeared in the original object. In negative polarity microforms, the colours and tones are reversed, with light areas appearing dark and vice versa. Negative images have much less natural contrast than positive images, but the contrast of negative images can be greatly enhanced when the microform is scanned and digitally post-processed – often producing cleaner and
more easily machine readable images.