Currently there seem to be two types of Exacta to Eos EF adapters available - one type is cheap, a simple converter that is recessed slightly into the camera mount and (just) allows focusing to infinity by the lens flange being more or less level with the front of the camera, the other has the lens well out from the camera body and presumably incorporates a corrective lens - it's a lot more expensive. Until a few days ago I would have recommended the cheap ones unreservedly - they work very nicely with manual stopdown lenses. But I've just had several lenses in with Exakta's version of auto-stopdown, which has a stop-down button in a side housing, and it turns out that it is impossible to mount lenses as they're supposed to fit. An example of the type of lens below: The adapter fits onto the lens before you put it onto the camera, and goes in with the side lump at the top. Except it doesn't because the bit that sticks out fouls the flash. It is possible to put them in at a different position, but then they don't lock on properly, and I think that there's a very good chance that they could get jammed and be impossible to remove without damaging the camera. It looks like the adapters with lenses bypass this problem, though there's probably some degradation of the image, so they may be a better option if you're really keen to use Exakta lenses.