The Nikon D40 did away with the built-in autofocus motor, among other things, from its body to minimize cost and be able to offer the new DSLR to more people at an affordable price. Since its debut, test reviews have confirmed that the D40 is a very capable DSLR, affirming Nikon’s design move.
Without the built-in AF motor, the Nikon D40 will have to use lenses with built-in AF motors. These are called AFS lenses.
Sigma has announced that it has a line of those AFS lenses, fully compatible with the Nikon D40 mount. Most of these lenses have the HSM motor in them with the exception of the 80-400mm f4.5-5.6 EX DG OS which is optically stabilized.
Sigma says the following are fully compatible with the D40:
10-20mm F4-5.6 EX DC
12-24mm F4.5-5.6
17-35mm F2.8-4 DG
50-500mm F4-6.3 DG
APO 50-150mm F2.8 EX DC HSM
70-200mm F2.8 DG MACRO
80-400mm F4.5-5.6
100-300mm F4 DG
120-300mm F2.8 DG
300-800mm F5.6 DG
14mm F2.8 EX
30mm F1.4 EX DC HSM
150mm F2.8 EX DG
180mm F3.5 EX DG
300mm EX DG
500mm EX DG
800mm f5.6 EX DG
[Site: SigmaPhoto.com]