Joey at Lensrentals.com has written an article on how to use lens adaptors properly. There are a lot of photographers out there with a mirrorless system to compliment their DSLRs, and it's nice to be able to use lenses on either system whenever possible.
From Lensrentals.com
Mirrorless cameras have become incredibly popular these days, saving a lot of users from the size and weight of bigger SLR systems out there. As consumers make that switch, they often want to bring their current lenses along for the ride. Thanks to shorter flange distances, this is physically possible, but in practice, it’s not as simple. Because of that, it felt necessary to explain the differences, the challenges, and what you might not know when going into a new system when a handful of adapters. Let’s break down the most popular options out there that we carry.
To start, we’re mainly talking about the following three camera systems that make adapting easier than the others: Sony E/FE mount, Micro 4/3s (Olympus and Panasonic), and Fuji X mount. Lenses from Canon, Nikon, Leica, and Sony’s SLT lineup, as well as third party lenses in those mounts, are all able to be adapted, with some degree of success. Read the entire article