Since a few people asked this is a short how-to on how I tune my adapters. As you will notice I am far from a perfectionist but so far my method has worked well for me and I think it could solve issues for some of you as well.
Correcting Infinity Focus
Most adapters, not only the cheap ones, are a bit too short. This means that the markings on your lens are off and you can focus your lens behind infinity so the infinity hard stop of your lens won’t work. It makes sense for adapter manufacturers to make their adapters a bit too short because your Sony’s flange focal distance varies a bit and so does lens calibration. If their adapters were exactly as thick as specified there would be quite a few cases were people couldn’t focus at infinity which is way more annoying than a focus scale which is a little off.
But a too short adapter can also have negative impact on the image quality if you use a lens with floating elements. Especially with fast wide angle lenses you can get serious field curvature issues as many users of the Metabones Canon EF adapters have found out.
Important notice: This fix only works if you can focus at infinity and beyond! If you can’t reach infinity the fix will only make matters worse.