I’ve seen those Nikon to Canon adapters discussed a few times on the DP Review Canon 300 - 500 - 1000 forum, but never seen any results. I bought one last year but hadn’t played with it much. So last weekend I mounted my 50mm f/1.4 (from around 1970) on my XSi (450D) and went wandering around town.

The details: My adapter always reports f/2. I used aperture priority, ISO 100, center point exposure and focus. I used the green dot focus indicator to determine focus at f/1.4 and shot one photo. Without refocusing, I then stopped down to f/8, f/11, or whatever, and shot another another. A few examples are below. See the comments under each.

At home, I set up a test stand to see what was going on. Tripod, 2 second delay, etc. I focused without the yardstick in place, then returned it to the position you see. The results confirmed my impressions from the outdoor pictures. I tried focusing at f/1.4 and stopped down as far as f/5.6, with the same result. The focus detection function in the Canon is somehow being fooled by the Nikon lens. Despite the little green dot in the corner saying focus has been acheived, the lens is actually focusing noticably in front of my target. Stopped way down, the images look much sharper, not unexpected. See the individual comments.

I also tried my Nikon 135mm f/2.8, and got the same result, focusing in front of the target.

I then tried my two Canon kit lenses (18-55 and 55-250), and they worked just fine with autofocus.

None of the images were adjusted in any way.

If you know how the focus system is being faked out, or what to do about it, please leave a note.

So I don't think my Nikon to Canon adapter is going to see much use.