So there is a lot of discussion about the conversion of apertures and depth of field between smaller sensors and full frame sensors. The main thing that I remember is that the depth of field doesn’t change during the conversion. What do I mean by that?
So if you have a 150mm lens on the MFT camera at F/2.8 that is the same as a 300mm at F/5.6 on full frame. For both these lenses, for a given focus distance the depth of field is the same. So if you are interested in trying to get a blurred or sharp background then remember that your aperture has doubled with the focal length.
That does make things difficult to get a really blurred background. With a full frame F/1.8 at say 85mm you can get a nice blurred background. To get the same depth of field (blurring) on MFT you would need a something around 42mm at well F/0.7. That’s not going to happen with most lenses.
There are two options on the market that come pretty close! There is the Panasonic 42.5mm F/1.2 ASPH Lieca DG Nocticron OIS lens, which in the UK is currently about £1150. Or there is the Voigtlander 42.5mm F/0.95 Nokton, which is £850. It should not be a surprise to you that these lenses exist for the exact reasons stated above.