D40 with a Nikon AF-5 DX 55-200 lens will not auto focus.. The 18-55 does auto focus OK...

If you're looking at the camera without a lens on it, there should be a little flat protrusion in the lower left. Make sure that it is protruding and not obstructed.

Some charts are on the web. Search for your model of camera and compatible lenses.

Take your camera in and have them fix it under warranty if your warranty is still valid.

hi ! iam too a D40 holder,u can opt for AF-s versions or HSM sigma,both of them autofocus on d40,can go for 18-200 AFs VR or if u need still longer end go for 70-300 but it is costly than the sigms 70-300APO DG HSM MACRO..,its a much better reviewed lens and dont forget the cost..anyway do some research before considering..good luck

with your D40, you can old go on manual focus on the 70-300mm AF-G/D nikkor.

The D40 (& D40X & D60) will not autofocus with the G series lenses. The three cameras above require a newer DX series of lenses for the AF to work.

The G series lenses won't work in AF mode on the newer, entry-level Nikons. They require the DX series.

Autofocus function on the D40 only supports lenses with the
AF-S feature, which have an autofocus motor built into the lens,
instead of using an autofocus motor drive built into the camera.

The Tamron lens you have, does not have a built in motor and
the autofocus function relies on the motor drive in the camera.

It will not work with the D40 or D60, but it will work with other
Nikon digital SLRs, such as the D80. Need to get an AF-S
type lens or upgrade to different Nikon digital SLR. Unless
you do this, you will have to manually focus the Tamron lens.

All of the Nikon DX (for digital) series lenses are also AF-S
type, so they will work with the D40, which is designed as
an entry level digital SLR, therefore it is intended primarily
for use with DX lenses, which are typically sold in a kit with
the D40. Most common one is Nikkor 18-55mm DX AF-S.

Other Nikon AF-S lenses made for film cameras (FX type)
will also work with the D40, but these tend to be expensive
professional models. DX series lenses tend to be more
affordable. You might consider the 18-200mm DX AF-S
as an alternative to the Tamron, but these are not cheap.

This lens, afaik, does not have auto zoom - it has auto focus.

sir, replace ur lens image reading sensor