Advance Densitometers is a device capable of measuring the degree of darkness (the optical density) of a potographic/semitransparent material or of a reflecting. The measurement is made by placing the sample between the Densitometer, which acts as a source of light, and a photoelectric cell. The presence of the sample between the densitometer and the photoelectric cell creates a difference, which determines the density of the sample. There are three types of densitometers: Transmission, Reflection and Combination. A Transmission Densitometer is used to measure the amount of light transmitted through a transparent material. Here, the densitometer determines the opacity for different areas of an original transparency or of the processed film negative or positive. A Reflection Densitometer determines the density by measuring the amount of light being reflected from a surface. It is also effective in calculating total dot gain, hue error, grayness, and other characteristics in printed pieces. The last type of densitometer can make both kind of reading, hence it is known as Combination. The advance densitometers are outfitted with electronic integrated circuitry for precise reading.