Chances are, when you first bought your SLR, you received a kit lens with the camera. Kit lenses are okay for beginners to use, but once you start learning more, youíll come to realise that there are many other speciality lenses out there that all have different focal lengths.
It can be confusing trying to decipher all the different terms used to describe lenses, which are always displayed on the side of any lens, like so:
The main information you need to be concerned with is the number (or numbers) listed before mm, which is the focal length of the lens. 50mm is considered to be ďnormal focal rangeĒ in comparison to a human eye. Anything below 50mm is considered a wider view, and anything above 50mm is a more magnified view.
To pick a lens with the right focal length for your needs, you need to do some research beforehand. Lenses can be very expensive, so when youíre ready to upgrade, youíll want to make sure you donít waste your money on a lens you wonít use.
1) Type of photography
Lenses are classified as either normal, wide, telephoto, macro or fish-eye. Kit lenses tend to fall within the normal range, and are fine for capturing everyday photos, but if you want to specialise in a certain style of photography, youíll need to purchase lenses that best suit the style of photography youíre most interested in:
Full frame SLRs have bigger sensors than entry level SLRs, and unless lenses are made to be used with cropped sensors (which some lenses are), the size of the sensor in your camera will determine how a lens impacts on your photos.
Full frame SLRs wonít crop the photos in any way, whereas SLRs with slightly smaller sensors will have a slightly different focal length. It isnít very noticeable, but it can make a difference when it comes to framing a subject, and the overall depth of field. Check whether the mount on the lens is suited to the size of the sensor in your camera before buying.
3) To zoom or not to zoom?
A zoom lens uses the optics of the lens to hone in on a section of the field of view and enlarge or shrink it in the viewfinder, while maintaining focus. The range in a lensí focal length when zoomed in and out is expressed in the number range on the side of the lens. For example, a 24-70mm lens, when zoomed out at 24mm, is as wide as it can go, and when zoomed in at 70mm, is as close as it can go.
Prime lenses are considered normal lenses without zoom, such as the Canon 50mm f/1.2L or the Nikon 50mm f/1.4D. They offer a fixed focal length that canít be altered, which ensures images are sharp. They also have narrower apertures than you achieve with a zoom lens, which makes them ideal for portrait photography, or in any situation where you want to achieve good bokeh. 50mm, 85mm and 135mm are some of the most commonly used primes, and theyíre a lot less bulky than zoom lenses.
I personally find it hard to use a lens without a zoom. I prefer having the flexibility to frame my subject without moving around too much, but Iíve achieved really good results using a prime lens - it just requires you to be very active on your feet!
4) Aperture limitations
The aperture is the f-number on the lens is either listed as one number, or as a number range. A lens with just one number is considered a fixed aperture lens, and a lens with a range is a variable aperture lens.
For example, with the 24-70mm f/2.8L, a maximum aperture of 2.8 can be selected when zoomed in at 24mm or 70mm, as can any other aperture above this number. However, with a 15-85mm f/3.5-5.6, the wider aperture of f3.5 will only be able to be used when zoomed out at the maximum focal length of 15mm. When zooming in closer, the aperture will vary anywhere between f3.5 up to f5.6, and will set itself on f5.6 when shooting at the closest possible distance of 85mm.
I think having a variable aperture can be a little frustrating, and most kit lenses tend to have variable apertures. I prefer to have control over the aperture no matter how my lens is positioned, and fixed aperture lenses tend to work better in low light, too.
All camera brands offer different types of lenses to suit their camera, but there are also two other companies who create lenses that are compatible with lots of different camera bodies - Tamron and Sigma. When deciding whether to purchase a lens created specifically for your camera brand, or one made by Sigma or Tamron, youíll notice the Sigma or Tamron versions are usually more affordable, but this is because their optics arenít perfectly customised, although they still work well. Youíll need to test out all the different versions for yourself before making a final decision.
There are also companies that make lenses purely for creative effects, such as Lensbaby. If youíre interested in experimenting with these, itís worth renting them before you buy, because they give very strong visual looks compared to traditional lenses.