When you compose a shot, and depress the shutter button 1/2 way - you should hear the focus motor run to find the best focus. You should also see the image eventually become sharper in the veiwfinder, during this time. Focus can only occur when there is sufficient contrast. If the area is dimly lit, the D70's focus assist lamp should come on (unless disabled in the menu) to help bring out enough contrast for focusing. It has limitations however.. it too dark, distant or still lacks contrast, the camera will not be able to focus. This is usually a problem for night time shots or poorly lit indoor shots with slower lenes. You shouldn't run into this problem on bright, sunny days or with a fast, prime lens.
The D70 and many Nikon lenses for that matter, have the ability to switch between AF and M focus modes. An image of the switches is below:
It is important that BOTH switches not
be in the M
position. Different lenses have different designations for Auto Focus. The one pictured on the lens allows for manual override when the lens is in the M/A
position. This simply means you can twist the focus ring on the lens without first needing to change the position of the switch to M
. It is a nice, handy feature. Other lenses without the M/A
position would require that the switch be moved first, an additional step that could be the difference in getting the shot - or not.
Make sure you're not trying to hand-hold the camera when the shutter "1 / 1.5 x Focal length". That is, if you're shoot at 100mm, you should use a tripod if the shutter speed is 1/150 sec. If at 300mm it would be 1/450 (or 1/500) of a second. At 50mm you should be 1/60 - 1/100 of a second. That's just a guide.. some people can hold it steadier than others and the new vibration control built in to lenses can lower that shutter speed too. If you're running into that as a problem, bump your ISO up one and try again.
THose are a couple of things to check out. Hopefully, one will solve your problem. Good luck! please rate my reply - thanks!