I have a Nikon D40 with a Nikor 18 -55 mm lens. When I try to shoot close up shots of small products for ads (beer bottles, ipods,. ) I can't get a focus on the entire subject. Is the short depth of field due to user error or do I need to get a different lens?[email protected]

One problem might be the place you are choosing to focus. The Depth of Field is found both in front and behind your "focus" point. It's easy in product photography to focus on the closest point of the item, which wastes some of the DoF capability of your lens because you have area "in focus" that is in front of the object you are shooting.

Also, you need to shoot with the smallest aperture available, which means you need either a lot of light, or long exposures.

You may find this online DoF calculator helpful in helping you determine the optimum place to focus, and to place your items. Using your Nikor 18 -55 mm lens at f/22 with your lens focused at a point 2 feet from your lens, you get:
Depth of field
Near limit 1.85 ft
Far limit 2.18 ft
Total 0.33 ft

If you stop down to f/32, you get:
Depth of field
Near limit 1.79 ft
Far limit 2.27 ft
Total 0.48 ft

Hope this helps!