The Densitometer

A.k.a. "three area procedure"

Densitometry makes is possible to produce standardized results, which is very important. But how does a densitometer work? How does it determine and measure colours?

With a densitometer, you can measure the optical density of a profile, i.e. it measures the degree of darkness.

Densitometry is actually the measuring of density, not colour. The densitometer detects a colour sample three times, each time using another coloured filter (red, green and blue). These filters correlate to the susceptibilities of the three types of the eye's cone cells. Hence, densitometers are also called three area analyzers.

The 3 resulting values (from 3 coloured filters) are:

Value for RED: Tristimulus value X

Value for GREEN: Tristimulus value Y

Value for BLUE: Tristimulus value Z

There are 2 kinds of densitometers: Reflection densitometers and transmission densitometers.

However, densitometers only have a limited precision, which is why spectral photometers are often used instead of densitometers.