Gossen Notes: What is the difference between incident and reflected light measuring?

The incident light reading measures the light which illuminates the subject. The reflected light reading measures the light which is reflected by the subject.

For the reflected light measuring, please direct the exposure meter from the camera to the subject. For the incident light measuring, please shift the sphere (white cone) before the measuring cell, go to the subject and measure to the camera. This is to guarantee that all light elements (e.g. stray light) are taken into consideration. Thus, the result is independent from the grade of reflection of the subject.

In the reflected light measuring, a soot-covered chimney-sweep would distort the result as much as a white apron-clad baker. Only the mechanic in a neutral grey overall delivers the correct result.

However, the exposure value/EV which is given by the incident light measuring is correct for all three persons.