Which Lens?

Before the camera there was the lens. The Greeks figured out that lenses bend and distort light. The Romans and later the Vikings realised you could light fires with lenses. Nicholas of Cusa, used it to correct eyesight. But it was an Arab scholar called Ibn Al-Haytham who invented the pinhole camera which is pretty much a basic lens. Not bad for pieces of glass named after lentils.

These days, lenses have come a long way. They still bend and distort light, but with much more finesse and accuracy, and the mechanisms have changed as well, zoom ranges, apertures and more recently image stabilisation. There are literally hundreds of different lenses on the market and for photographers this is a very practical consequence. It means you have to think carefully before buying a new lens. So here are a few points to consider first.

1. Lenses are not interchangeable.
This means that lenses made for Canon cameras don't fit on Nikon DSLRs. It's a bummer but it means you have to be really careful about what lens you are buying. Make sure it has the mount appropriate to your camera. The easy route is to buy Sony lenses for Sony cameras or Canon lens for a Canon camera as an example but for Nikon this doesn't always work. Nikon D40, D40x and D60 have come with a pesky new mount which limits what Nikkor mounts they can autofocus on. To make things more complicated, third party lenses, such as Sigma and Tamron will produce cheaper lenses but sometimes for only certain brands or certain mounts. You have to make sure the lens you are looking at will fit on your camera.

2. Determine your focal length
Focal length is determined in millimetres. It basically signifies how big the image is magnified, so how close you have to be to the subject. Lenses come in fixed focal length, which means you can't zoom in or out, or with a range of focal lengths. Depending on what kind of photography you want to concentrate on, the focal range matters a lot. Standard lenses are between 35mm-105mm and this range is good for portraits and taking photos of things like flowers. Wide angle lenses have focal lengths shorter than about 28mm, and are good for taking landscape photographs. Telephoto lenses are lenses that fall somewhere between 100mm-300mm, can magnify distant objects really well and therefore are good for bird watching and wildlife photography. Super-telephoto lenses go beyond the 300mm mark, and that's for anyone who really wants to capture wildlife shots.

3. Prime lens or zoom lens
If you know what focal length you will be working with the most, you might want to consider a prime lens. It's another name for Fixed Focal lenses, so they have one focal length which can't be changed. This might not sound appealing at first, but prime lenses have an advantage over zoom lenses. They tend to take much clearer photos because they don't have as many moving parts and the lenses are very accurate. They also come with small f/stops which means bigger apertures and which again means clearer sharper photos. Zoom lenses on the other hand provide versatility. If you like taking photos at 18mm, 35mm and 50mm, you might as well just get an 18-55mm lens than to carry around three different lenses. Going out hiking and trekking is all fun and games until you have to carry a ton in gear. A good zoom lens will make life easier.

4. Maximum Aperture
A wider aperture allows in more light, which often makes for clearer brighter photos, especially in dark situations, so having a lens that allows a wider aperture is an asset. Most lenses will allow you to set it to very small apertures, like f/16 or more, which has its uses. A smaller aperture means greater depth of field. A large aperture means you can create Bokeh, take good pictures with natural light, even if it isn't that bright and faster shutter speeds to prevent blur. But you don't always need the widest aperture on your lens, unless you like taking photos in dim light situations such as indoor portraits. Lenses with wide apertures are often pricier and heavier since they need wider barrels.

5. First party or third party lenses?
If you have a Canon Camera, it makes sense to buy a Canon lens, which is a first party lens. You can be sure they are compatible (unless you have a Nikon D60, where they don't take all Nikkor lenses) and have a reputation for quality. But if price is an issue, you could consider a third party lenses such as Tamron or Sigma. The trade-off is often quality, but sometimes third party manufacturers make very good lenses that don't have first party matches, they sometimes have a bigger range of lenses with different focal lengths but again you have to check to make sure the lens mount is compatible with your DSLR.

6. Optics
You'd think all lenses were created equal, but unfortunately this just isn't so. Many come with little extra features like Special Low-Dispersion (SLD) glass for Sigma, Extra-low Dispersion (ED) glass in Nikkor lenses and Low Dispersion in Tamron lenses. There are many denotations, but basically they all work to prevent distortions in images that happen when all the points of light don't translate back into single points. You might see flares, or something called chromatic aberration, when the colours are misaligned. The annoying aspect of lenses is that each manufacturer gives a different name to the methods they've used to prevent image distortion, though they are basically the same methods. Most lenses come with some optical extras to prevent image distortion but it's a good idea to check before buying your lens.

7. Image Stabilisation
Some cameras, like Sony and Pentax DSLRs come with In-body image stabilisation which means you don't have to worry about investing in a lens with Image stabilisation. They tend to be pricier anyways. But don't despair all ye who have DSLRs that don't come with in body image stabilisation. Firstly, in lens stabilisation is considered to be better as it shifts the image before it hits the sensor rather than move the sensor to try and compensate for a shaky image. Secondly, you could just invest in a good tripod. However, if you are the type of person that likes to walk around and take shots on the spur of the moment, some form of image stabilisation will be useful, especially if it isn't very bright and you need a longer shutter speed to capture the image.

8. Price
Ideally price is the first thing to consider, but you should become well aware of all the points above then think about your budget and see what that allows you. If you are on a tight budget then quickly think about what is most important. Would you give up a large aperture or image stabilisation? Is having a third party lens something you would consider? Think about what is most important, whether it's focal length or optics then consider your budget and what you can afford to invest in. The best thing about lenses is that they don't tend to depreciate. Two years later your camera body might not be worth as much, but the lens will still be valuable.

Finding the right lens can be a challenge, but if you consider the steps listed above it should become quite easy and limit the options open to you so you can make a more informed choice. After that all you need to consider is what to photograph first.