How can I tell if a nikon lens is ai. I have a d200 and a d7100. I'm using a dx 12-24, and non dx nikon 35 - 70 and 80 - 200. I also have an older 200 - 400 that I've used successfully on my d200 and a 24mm prime non dx. I originally bought those lenses for my now almost worthless N90s cameras. Would they (the 200 - 400 and the 24prime) work on my D7100?