How the crop factor affects Lens hacking
An 85mm lens doesn’t have the same angle of view on a APS-C sensor camera as it does on a full frame sensor. The APS-C camera has a crop factor of 1.6 which means that an 85mm lens on a Canon 30D is equivalent to a 136mm (50 x 1.6) lens on a 5D Mk II.
Because Micro Four Thirds cameras have a crop factor of 2, a 50mm lens on a MFT camera is equivalent to a 100mm lens on a full frame sensor camera.
Select your lenses based on crop factor
To shoot wide, use a 20mm lens on a full frame sensor camera. You will want a crop factor of 1 for wide angle shots.
To shoot telephoto, use a Micro Four Thirds camera. The 2X crop factor on the MFT camera will turn your 300mm lens into the equivalent of a 600mm lens.
Lightweight, slow lenses from the 1950’s are fun to experiment with on a MFT camera and you can pack more into your bag. If you have an Olympus, you have image stabilization for every one of those lenses.