#11. "RE: Difference Between D50 and D40 , D40x" In response to In response to 10 Sun 22-Jul-12 10:57 PM by briantilley
This is a 4-year-old thread, but it's probably worth pointing out a couple of things - for posterity, if nothing else
It's true that "screwdriver" AF lenses have a pattern of electrical contacts that differs from the AF-S lenses that will not autofocus on the D40, D40X, D60, D3000, D5000, etc. The pattern on AF lenses is one contact, then a gap, then four more contacts. AF-S lenses have no gap and have between 7 and 10 contacts in one group.
Whilst the absence of contacts does mean it's an MF lens, the presence of electrical contacts does not guarantee it's an AF lens. There have been a couple of so-called "Ai-P" manual focus Nikkors (such as the 45mm f/2.8), which have the same "one-gap-four" contact pattern as screwdriver AF lenses.
Lastly, all the top "pro" Nikkors have the same contact patterns as the cheaper, plastic-mount, lenses that you mention. The number of contacts is not an indicator of quality.