>Both my lenses are autofocus, and the one I'm borrowing from >my friend (something to 300..not sure if it's 50) is also >autofocus. The 70-210 is a 35mm lens but is not Non-CPU; >that's why I'm confused as to the problem I'm having with it. > > >Thanks for any help!
Is the 50 to 300mm lens a Nikon? If so it has to be manual focus. Nikon never made that lens as an AF. Maybe you have the AF 70-300mm. Nikon made the 70-210mm zooms as both manual and auto focus. That's why I asked. If it is an AF lens make sure the contacts on the lens are clean. When you turn on the camera with it attached do you get an error message? If so make sure the lens is locked to the smallest aperture like f32. I have both the f4 and the f4-f5.6 AF 70-210MM AF lenses and they work fine on my D300.