Abstract: An automatic scanning densitometer which is self calibrating and accurately measures highlight density, shadow density and tonal distribution of midtones occurring in the subject matter of the photograph to be reproduced. A reflection densitometer is disclosed which in one or more scans identifies and measures first the highlight and shadow densities and the tonal distribution of the subject matter to be reproduced, as opposed to the background of the photo. The instrument automatically determines the size of the original and, with an input to the device, the size of the window in which the original is to be reproduced to provide enlargement or reduction. Measurement of density values are uniquely stabilized and with the use of a monolithic sensor on a single substrate the entire image is processed and measured, not just target areas which must be manually measured or aligned with an apertured scanning bar.