The Contax/Yashica lens to Canon EOS camera adapter without negative glass sure looks like a relatively new development; I was only aware of the one by Kenko which has the negative element.

On the same note, I have two adapters with negative elements for using Minolta manual focus lens on autofocus camera, one offers no automation and seems to carry no maker's mark, only "Adapter MD/Maxxum", which seems to be easy enough to use even with no automation coupling. The other is a Sigma 1.6X converter which not only offers diaphragm automation couplings but autofocus as well; I have contacted Sigma but they couldn't be bothered to send me a manual so I am not sure how to use it either with a Minolta lens or even a M42 lens via a Minolta P-Adapter. Any thoughts on that?