[JJ_SO]

No BC, I'm not looking for straw man arguments, I'm basically following the ones I read before - and there was the generalisation that a FF sensor, no matter what, gains about 2 stops of light. I know it has to be sort of same generation sensors, but that wasn't said - it's just that all of these simple equivalencing calculations fail with reality of so different sensors, RAW-converters and also to say this lens is just that other lens, only slower and longer - misleading and  not helpful.

 

There is no camera which is the exactly scaled version of a smaller or bigger one. Therefore you have a nice formula, one just needs to build teh devices fullfilling it.