All lenses with Nikon mount are compatible with Nikon D40. If the question rephrase : "What lenses are able to autofocus with Nikon D40", then the answer is : the new Nikon AF-S lenses (with Silent Wave Motor inside), Sigma lens bearing HSM code, and upcoming Tamron lenses (18-200mm, 17-50mm and 70-300mm).
There is a wide selection of lenses you can pick most nikon lenses would fit but diffrent companies like telephoto lenses wont autofocus because the nikon d40 autofocus motor is too small.
Yes, but they won't act the same on a D40 as more expensive Nikons. Only AF, AF-D, AF-S, and G lenses will meter on a D40 and ony AF-S and G lenses will auto focus on a D40.
No, Canon lenses on Canon; Nikor lenses on Nikon.
Yes. The lens' brand (Nikon for example) to your Canon adapter.
It doesn't depend on the camera body, it depends on the size of the lens. DON'T confused size of lens for focal length. If you can't find the specs for your lens, just measure it.
It depends on the make of the lens and the mount type. Newer Canon lenses have an EF mount while Nikon lenses have a Nikkor mount. Though you can purchase conversion kits to put a Canon lens on a Nikon and vice versa.
not without a converter. but then it becomes a completely manual lens. focus, meter, everything.
Yes
Yes, it will fit. However, you will still need to see if the lens you have has or does not have features like autofocus or CPU connectors that will carry all the info that your camera needs... If it is a Nikon Lens it will work fine. So will others like Sigma, Tamron and Tokina. Carl Zeiss may not give you all the functions but will work in manual mode.
nope
yes, sure can
yes
No
Yes. And that is an AMAZING lens, by the way.
The Canon AE1 lens will not fit a Canon digital. You can buy an adapter that will allow the lens to work in manual focus mode on the digital camera.