Nikon D3100 Lenses, I have an AF-S Nikkor 18-55mm 1:3.5-5.6G What do these numbers mean?

I would like to buy a lens that would allow me to focus and take shots at a longer distance, so what numbers on the lenses should I be looking for? I'm new to photography as you probably guessed!

The 18-55mm refers to the focal length, which in this case is wide angle to mid-range. If you want further 'reach' (ie to fill the frame without having to get closer to your subject), then you need bigger numbers for the focal length. A reasonable complementary lens to the one you have is the 55-200mm lens which extends the range you have now.

The other numbers refer to the maximum aperture (ie the amount of light you can let in). With cheaper consumer lenses, the max aperture is variable - you'll get f3.5 at the 18mm end but only f5.6 at the 55mm end.

So called 'pro' lenses tend to be 'faster' - they are capable of wider apertures throughout the zoom range, eg 70-200mm f2.8 lens gives yo f2.8 at 70mm AND up to 200mm. This lets in a lot more light and allows for faster shutter speeds. You pay a price for this though - Nikon's 70-200mm is around £1600.

The lens designations can really be confusing. Here is a webpage that shows the numbering systems for all popular manufacturers of lenses:

http://www.althephoto.com/lenses/concepts.php

For focal length, understanding what the different focal lengths represent is also helpful. This webpage will show you the difference between 20mm and 200mm:

http://www.althephoto.com/concepts/lenses.php

Finally, a Nikon AF-S 55-200mm is a popular second lens for your camera, and Nikon even bundles it in a two lens kit:

http://www.amazon.com/...000O161X0/

And if you want a bit more reach, the 55-300mm is often bought. However, I don't recommend this lens, but rather the Nikon AF-S 70-300mm as it is a superior lens to the 55-300 (and don't worry about the gap between 55 and 70mm.

http://www.amazon.com/...000HJPK2C/

Although this lens is a bit expensive, you can sometimes get it refurbished for a good discount.

http://www.adorama.com/...AFVRR.html

If you buy the 70-300mm refurbished, it is a better deal than the 55-300mm.

Be aware though, not all Nikon 70-300mm lenses will work on your camera. It must have "AF-S" in the model name or it will not autofocus on your camera. To date, there's only one AF-S version of the 70-300mm, but several AF versions - which will not autofocus.

Your D-3100 Nikon camera body has a smaller image sensor than some other models, so choose those Nikon lenses that are marked "DX". The "G" on lenses for your camera indicates the lens does not have a built in mechanical aperture control ring. You don't need this ring because the aperture control for your camera is built into your camera body. The DX lenses are lighter than those made for larger sensors, such as the professional models.

When choosing the lens for a longer distance, you decide how much magnification you want to have. I have a Nikon body like yours that takes DX lenses, and also have the 18-55mm which is an excellent lens. If you are interested in nature photos, including birds, then the 55-300mm gives you a tremendous range, including for taking birds and other animals where you can't get close enough. This lens is reasonably priced.

For any telephoto lens for your camera, get one that has "VR", which is "Vibration Reduction". On a tripod, you don't need VR, but usually, for me anyway, a tripod is good only for stationary subjects. For nature or young children, you need to take the picture before it moves away. Hand holding and VR can work really well, especially if you learn how to hold your body and the camera reasonably still without a tripod.

The Nikon 18-200mm lens that is DX and has VR is also great if you want to carry only one lens and you don't want to carry and change lenses. Not as well suited for nature and child photography as the 55-300mm but more versatile. It is also a lot more expensive than the 55-300mm.