I have been in the market for a used 24 mm and came across one today. I read the archives as well as Moose Peterson's Nikon System Handbook. I have these questions: 1. what is AI? (I know it means auto indexing, but what is that?) 2. the man behind the counter said this lens had been "AI-d". A section was cut away which, apparently, makes it "AI-d". If he was correct, what does this mean? 3. What do I lose/gain with this lens vs. a new AFD? I know I will not have distance information. That's okay. I plan to use it for landscapes, and I love its "real" depth of field scale on the barrel. I assume I lose matrix metering. My LCD suggests I retain center-weighted and spot metering. I assume metering is available only in S and A modes. Any thing else I lose? What can I gain from this classic? Thanks for any insights you can give me! God Bless! Robert Madden