What camera lens would be best for zoom?

I would like to buy a new lens for my camera (Nikon D40) which can zoom far to take pictures of birds/nature.

I'm not a professional photographer I just do a bit now and then for fun but I know nothing about the different lens types.

What would these lens types be best used for?
75-300mm
100-400mm
500-1, 000mm

Nikon has an online lens simulator

http://imaging.nikon.com/...simulator/

I think this will help you.

There's more to a lens than just the focal length, the speed of the lens (how much light it can let in) and how it will work to focus with your camera are also important. With the D40 you also need to remember that you need a lens with a focus motor in the lens. Most cameras have this in the body, but Nikon has always left this out of their entry-level DSLRs.

None of them. Best lenses for long range photographs don't zoom, this is because of the engineering difficulties to make supertelephoto lenses.

I would be looking a 300mm or 400mm prime lens instead.

Have you also considered Nikon's 55 - 200 VR? (see link below) It doesn't have the same reach as the ones you've listed, but it's a very decent lens with a respectable reach, and is very affordable.

The 75 - 300 mm is in the same class but has a bit more reach and is more expensive, whereas the Nikon 80 - 400 mm is a $ 1, 500+ beast of a lens, and more often than not needs a tripod to get sharp results. It's also Nikon biggest zoom lens, and is primarily aimed at photographing static subjects, not action shots like sports etc. Nikon biggest, current tele (not zoom) is the 600 mm, and can be yours for a mere $ 10, 000.It weighs in at 11.2 lbs, with a length of 17.5". You can get larger zooms from non-Nikon brands, but their image quality usually isn't up to standard.

Lenses (zoom or otherwise) with a focal length of more than 300 mm are usually specialist lenses for nature photographers etc. With a price to match. More common are the so-called fast f/2.8 70 - 200 mm lenses used by photojournalists, sports and wedding photographers etc. The big lens opening (f/2.8) lets them shoot in low light, but it also means that the construction of these lenses is necessarily large and somewhat cumbersome compared to the much lighter 55 -200 mm and 75 -300 mm lenses. The latter two, could be categorized as multipurpose tele-zooms, lightweight and much more affordable than the larger and/or faster zooms.

The millimetre designation stems from the days of good old film cameras, and nowadays also applies to so-called full-frame (FX-format) digital cameras, which have digital sensors that are the same size as a film negative back then. Your D40 however, uses a smaller, so-called DX-format sensor to capture an image which means that any focal length must be multiplied by a factor of 1.5. A 55 - 200 mm lens for instance, effectively becomes a 82.5 - 300 mm on your D40. Keep this in mind when you try Nikon's excellent lens simulator as someone's already suggested.

Other popular and reputable lens makers other than Nikon are Tamron, Tokina and Sigma. Their lenses tend to be less expensive than the original Nikon lenses. Hope this helps. Happy snapping.