I recently noted that Lumix are to bring out a 42MP micro 4/3 and a 100-400 pro grade lens ...Good I thought make a great bird combo for more POI. Then I went oh no the iso sensitivity is bad at 800 v the FX at 3000 so thats out. So I took my old D800 (I keep the good cameras in the floor safe) and photo in the garden FX 1/80 F8 iso 200, Then I switched it to DX still 1/80. Then I fetched the old D3200 ..still 1/80 and no doubt if I use a M4/3 I would still have got 1/80. The light falling on the sensor is just as bright whatever the size of the sensor right? ( I said brightnes not quantity) So if a camera is just a lens in front of a sensor whats going on? DX sensor half the size of FX so half the sensitivity and 4/3 is 25% of FX so thats a quarter sensitivity .. Now I know that these ratings are based on noise levels (-30db) so are they saying that a 25% crop on my D850 if taken at over 800 iso will be as bad as a M4/3? My neighbour who is a 4/3 fanatic does not follow it either.