The Olloclip can also help users get their iPhone better protected against bumps and it’s an impressive additional lens for owners who use the rear-facing 5Mp camera more than occasionally. iPhone users can now purchase Olloclip for $69.99 a pop from various sources, including Amazon.
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Anthony gave a very good answer, some of the older Nikon lens will work, to a point.I have a Nikon D200, and use some lens that I bughot back in the ’70 s,but I do have to focus these manual lens.I have a 75-300, 4.5-5.6 Auto Focus, that IS completely auto, everything works great.I don’t think the D40 will use as many auto features of some lens, as the D200, but no sure there?I also have an 18-200 VR lens, and if you are looking for a single lens that does a lot, I really like it.It is on my camera about 80% of the time.I like that I don’t have to worry about dust/dirt, changing lens in the field.