CNET Australia's lens buying guide is a comprehensive look at what lens to buy when you are thinking of moving beyond the kit lens that came with your digital SLR.
If there is some terminology in this guide that is unfamiliar to you, make sure to read our Learning Centre for full explanations. Each brand will have a dedicated lens range for its digital SLRs, and don't forget in some instances you may be able to use older lenses on a new camera.
As a general rule for beginners, you need to buy the same brand lens as your digital SLR. So, if you own a Canon camera, you'll need to buy a Canon lens or a lens that is marked as being compatible with the Canon mount. Third-party manufacturers such as Tamron, Sigma and Tokina, will make lenses compatible for all the major camera brands.
Note that this isn't a comprehensive guide to every lens that's available for every brand of digital SLR, but it will hopefully give some general information that is useful for making an informed choice based on your style of photography.
Most digital SLRs will come in a kit with one or two lenses to get you started. These lenses will usually cover the most common focal lengths that photographers will need. Usually, kit lenses will be in the focal length region of 18-55mm and 55-200mm.
A kit lens is a zoom lens, offering flexibility because of the range of focal lengths available within the one unit. In general, the body is made of plastic and is not as optically refined as a dedicated lens in its respective area (such as wide angle, standard or telephoto).
Use for: everyday photography
Any lens with a focal length less than 35mm is classified as a wide angle. This means it has a wide field of view, allowing you to fit more of your subject in the frame.
Ultra or super wide-angle lenses are characterised by their focal length being less than 24mm. Note that some wide-angle lenses tend to distort straight lines, a characteristic known as barrel distortion. Usually, wide-angle lenses afford the photographer a greater degree of depth of field compared to standard or telephoto lenses.
Use for: landscapes, street photography, group shots
Prime or fixed focal length
Prime lenses have just one focal length (that's right, no zoom). This means that they are generally very sharp and can open up to wide apertures, perfect for portrait photography and achieving that blurred background look. Prime lenses are lightweight compared to zoom lenses, and can be considerably cheaper; as an example, the Canon EF 50mm f/1.8 can be bought for AU$150 whereas a 55-250mm will be closer to AU$400 outright.
As a trade-off for all this goodness, they usually don't have image stabilisation built into the lens body. Prime lenses can be any focal length, but the more common ones available are in the standard focal length range; anywhere between 35mm and 80mm. The happy medium is a 50mm lens which lets the camera capture a scene roughly equivalent to how the human eye sees it.
Use for: low-light photography without a tripod, portraiture, street photography
A telephoto is the ultimate lens choice for photographers who want to shoot from a distance, getting in close to their subjects. These are generally large, bulky lenses, and depending on the level of magnification and maximum aperture, will be classed as semi- or professional lenses. As a rule, the wider the maximum aperture (eg, f/2.8) the more expensive the lens.
Telephoto lenses can come in prime lens variants or zoom variants. Telephoto lenses have a smaller field of view than wide-angle and standard lenses. They also have a tendency to "flatten" the image plane, and afford the photographer less depth of field.
Use for: shooting subjects from a distance, wildlife, sports photography
For those wanting to get into macro photography, or taking close-up images of plants, animals or objects, a macro lens is a must-buy investment. True macro lenses have only one focal length and some can focus to 1:1, or life size.
Use for: close-up, macro photography
Want to experiment with some fish-eye lenses? Perhaps some tilt-shift photography is more your thing? There are lenses available that will cater to pretty much every whim that a photographer may have. These lenses do tend to break the bank a tad more than standard lenses, and will have limited applications beyond their intended use, so buyer beware.