The adapter ring can be used to connect lenses with different bayonets, but it may not work properly. For example, Canon's EOS is an electronic aperture. Switching to other lenses may not be able to adjust the aperture, and there are problems such as no autofocus, no focus prompt, and no metering. Because the bayonet is a very complicated part, each company's bayonet contains many patented technologies, and the adapter ring can't completely make the lens universal.