Sat Mar 29, 2008 3:42 pm
Nikon USA says the D-40 will run all AF-S lenses. This is or was a flagship comsumer body and one of the primary consumer lenses, so it ought to work. I suspect a problem with the lens mount itself. I have issues with an 18-135 of this same AF-S G series. The plastic mounts can have enough play in them such that the contacts do not line up and the lens goes dead. Not a fan of plastic lens mounts. When mine acts up I find by gently shifting the lens on the camera the stars realign, and viola the lens works. Another possibility, is there may is a focus priority release mode, in which the shutter does not release unless the image is in focus. The D-200 has the "feature". It can be overridden. Finally, the AF system is finicky at f5.6. 5.6 is the minimum at which the system will function. If you're shooting in low light, at 5.6 sometimes the AF doesn't get enough light to work and it will refuse focus. Normally though I believe in this condition the lens will hunt, as oppose to not focusing at all. Lastly another of those questions that we hate to ask but need to be asked, your battery is fully charged? Any other signs from the camera itself that there might be electrical issues? Plaintive desire... better, faster non pro wide/zooms from Nikon.....