The lens works fine on a Nikon and has been tested on a F3. The tab was included on the lens to engage the matrix metering on the Nikon FA and F4 bodies (it will still work for that as it's only shaved down 1mm) but otherwise it's just there to hold the protruding rear element off a table if you set the lens down. I have an adapter which will mount any Nikon lens to a Canon body. http://www.adorama.com/CZNKEOSA.html