Quote Originally Posted by noparking View Post
When I went to check its accuracy by comparing exposure readings with my Olympus E-P1 the exposure values reported by the light meter in reflective mode (i.e., spherical diffuser moved to the side) are way off. (I have to adjust the exposure factor from 1 to 4 to get the Goessen reflective value to match the E-P1's). Here's the odd part, when the Gossen is in incident mode (i.e., spherical diffiuser is inline with light sensor) the exposure reading of the Gossen matches ~ that of the E-P1.
1 to 4 EV of difference?

Maybe you know it but I would like to clarify: one uses incident light metering and reflected light metering in different ways.

Incident light metering: the light meter is placed in front of the subject, the cell with the dome pointing toward the camera.

Reflected light metering: the light meter is placed near the camera, the cell without the dome pointing toward the subject.

If the subject is of average brightness (reflectivity) you should have more or less the same exposure always.

For an accurate comparison you should measure, while in reflected light metering, a grey card without projecting your shadow on it, filling the entire frame with the grey card. That should give you a value which is very close to the incident light metering.