My main digital camera is a Canon 1Ds mk2. It’s a full frame camera from 2004, I believe. I have grown fond of using vintage manual focus lenses on it. Mainly Nikon F mount lenses, but also a couple of M42 lenses. That is all fine and dandy with a cheap adapter from Amazon or Ebay. Or so I thought.
If you get an adapter without focus confirmation and have an older EOS body, you might run into a little problem. But before you get to modifying your adapter, test it. If it works, modification is a waste of precious shooting time.
On older EOS digital bodies – probably also on EOS film bodies, there is a little pin on the left side of the lens mount. When you mount a lens or an adapter, this pin is pushed up. For some reason though, it has to be able to move down when something without a focus chip is mounted. But the flange on the adapter prevents that. If you try to shoot your camera with an adapter mounted, the mirror will open and then lock up and you have to switch the camera off and on again for it to pop down.
To solve this, I actually filed off a piece of one of the flanges, as you can see on the pictures above. Now, which flange do you file? Answer: The one on the opposite side of the red EF-mount dot, as you see.
When you have finished filing your adapter, make absolutely sure there are no metal filings or metal residue of any kind left on it. If it gets in your camera, it can mess up quite a few things. If it is a digital camera, it can damage your sensor severely. I had a piece of metal get stuck by the lens contacts which caused my mirror to jam, just like what happens if you don’t file the adapter. This happened while I was using a fully automatic AF lens, so needless to day, I almost pooped myself, thinking my camera had broken. Lucky for me, when I popped off the lens, a piece of metal filing fell out and all was good again.