[Klaus]

This is not correct. Iso 100 is iso 100. If that weren't the case, you'd need a different light meter for every different sensor size and/or film format. That the one sensor has 4x the noise compared to the other at the same iso inder the same lightign conditions is a different matter altogether.

 

All you can state in this regard is that a 4/3 sensor is not the same as a FF sensor, noise wise, when images from these sensors are displayed or printed at the same size, with images taken of the same subject under the same lighting conditions - note that noise levels change with different lighting conditions as well, provided the sensor is capbale of capturing the different light levels, i.e., no under- or over-exposure. In order to get equivalent noise levels on a 4/3 as on a FF sensor, you need an exposure capturing 4 times the amount of light per square unit, or the same total amount of light. It just happens that iso is an easy way to manipulate this. At 100 iso you capture 4x the light than you do at iso 400. This is where this whole misunderstanding of "iso equivalence" originated from.

 

Kind regards, Wim

 

This is what I wanted to express - ISO 100 (MFT) is not identical to ISO 100 (FF) because the noise level (aka amplification) is different.