The lack of electrical contacts seems to cause problems with manual focus with some lenses,Canon 35mm F2.0 on Eos M (1st generation- focuses fine- seems to expose correctly)Canon 40mm STM- manual focus didn't work, it seems that this lens needs electrical contacts to be able to focus manually- weird-I bought a slightly more expensive product with electrical contacts and there were no manual focus issues.
19/08/2016