Mount adapters are incredibly useful for their ability to make lenses from one manufacturer usable with camera bodies from another. But do they have any impact on image quality? LensRentals' Roger Cicala, not one to take manufacturer's claims at face value, has done some investigation. Knowing that slight mis-alignments between a lens and even its native mount can cause softness in images, the added complexity with a lens adapter in the mix seemed likely to cause more problems. His findings are indeed interesting. 

In his blog post, Cicala takes a thorough and technical look at the effects of lens adapters on the measured edge-to-edge sharpness of a lens. His focus is mainly on whether commercially-available adapters would be good enough for testing lenses on an optical bench, which is a pretty demanding application. As usual, though, he brings a unique insight to the issue, from being able to test a large number of high quality adapters from the likes of Metabones and Novoflex.

In real-world use shooting 3D subjects (rather than planar test charts), we've found very little evidence of lens adapters having a serious impact on image quality. Still, his report is worth reading if you're interested in adapting your camera to accept different lenses.