Can you please tell me why the Tamron 18mm - 270mm lens stops focusing on a Nikon D90, I purchased one for my daughter and with in a few months she started to have problems, looking on web forums this is NOT uncommon, what do you have to say about it.
Her description of the fault is as follows,
1) The camera is turned on with the lens in situ – it works fine for a say 15 minutes and then the Nikon error F_ _ is displayed on the screen denoting a none compliant lens is fitted.

2) I switch the camera off, take the battery out. Then re fit the battery and switch camera on.

3) The camera works again at whatever focal length the lens was set to, but if I change the focal length say from 18 to 100 it will again cause the F_ _ error and the lens fails to autofocus and ‘dies’.

4) At first I switched the camera off and then back on again the lens re set itself and worked for another few minutes, but as the day progressed this became less and less likely to resolve the issue and a hard reset was necessary all the time.

5) Two Nikon lenses were tried on the camera with no fault occurring.
Have you had anything like it ? do you know what will fix it ? on some forums people have had 2 or 3 replacements & all do the same in time.