Zoom lenses are very different to fixed length prime lenses. For general everyday photography and walk about photography a zoom lens does have the upper over a prime lens, and are also more popular than prime lenses. When deciding on the most suitable zoom lens the first thing to consider is the required focal length, i.e. the minimum and maximum, that is needed to achieve the desired images. For example, it is possible to buy wide angle zoom lenses that have a focal length of 10mm – 20mm, such as Canon’s excellent EF 10mm – 20mm f/3.5-4.5 USM, or a super telephoto lens with a focal length of 100mm – 500mm, such as the Sigma 50mm – 500mm f/4.5-6.3 DG OS HSM or the professional grade Canon EF 100mm – 400mm f/4.5 – 5.6L IS USM.

Even though all of the above lenses are zoom lenses each one is used for a different type of photography discipline. Being a wide angle lens the Canon 10mm – 20mm is most likely to be used for landscape photography where as the Canon EF 100mm – 400mm f/4.5 – 5.6L IS USM and the Sigma 100mm – 500mm are most likely to be used for motorsports and/or wildlife photography. So, if the passion is landscapes the wide angle is best as the reach is not required, and if wildlife or motorsports are the passion the super long telephoto lenses are best.

The lenses described above represent the extremes and there are many lengths in between available for the photographer. Such focal lengths include 18mm – 55mm, 24mm – 70mm, 50mm – 150mm and 70mm – 200mm. Many photographers claim the 70mm – 200mm covers the most useful range making it very versatile. As such, all major manufacturer’s make a lens of this focal length so it makes no difference what digital SLR camera you shoot. Canon users have the Canon EF 70mm – 200mm f/4L IS USM whereas Nikon users have the 70mm – 200mm f/2.8 VR.

The second thing to consider is the speed of the lens, i.e. the widest aperture or lowest f stop. The speed required will depend on the main type of photography. Indoor sports and low light photography require fast lenses to ensure shutter speeds can remain high enough to eliminate camera shake therefore the lenses require a low f stop. Landscape shots are often taken with small apertures to ensure maximum depth of field and front to back sharpness. Because of this tripods are often used therefore a slower lens can be used in these situations. A further consideration is whether the shots are to be taken hand held or whether some kind of support, such as a tripod or monopod can be used. If it is not possible to use a support because, for example, they are forbidden which is often the case in public galleries, museums or churches, a faster lens is needed to eliminate camera shake. If it is possible to use some kind of support then a slower lens can be used as camera shake will not be an issue regardless of the exposure time.

A very useful feature in a lens is image stabilisation technology. Put simply this allows the photographer to use slower shutter speeds and achieve sharp shots. Some lenses, such as the Canon EF 70mm – 200mm f/4L IS USM allows the photographer to take pictures 4 stops slower and still achieve the same level of sharpness as a lens that does not contain image stabilisation technology. The only disadvantage of image stabilisation technology is that it adds to the weight and the price of the lens, often pushing it out of the reach of many keen amateurs.

Once the focal length and speed have been decided choosing the lens is simply a matter of finding a lens that has all the desired features, although this is easier said than done. Fast and long reaching zoom lenses with image stabilisation are very expensive therefore the photographer often has to make a compromise unless cash is not an issue that is.

Arguably, the most expensive lenses are made by Canon, Nikon however these lenses often contain professional grade optics that are capable of producing stunning images that are sold to make a living. Before spending thousands of pounds on these professional grade lenses the photographer needs to ask himself “are such professional images required?” If the images are to be sold and the lenses are required to make a living the additional expense can be justified, however if photography is simply a hobby the cost may be a bit more difficult to justify. All keen photographers would love a kit bag full of Canon or Nikon professional grade lenses full of the latest technology but most amateurs really don’t need such elaborate equipment. Fortunately, there are many third party lens manufacturers such as Sigma, Tamron and Tokina to name but a few. All of these produce lenses that are capable of producing some excellent images.

Before spending money on zoom lenses it is advisable to do a bit of research. Scour the internet and read some reviews about the lenses that are being considered. List the advantages and disadvantages of each and identify what features are a necessity and which ones can be done without. Join some photography forums and post some questions. Have a look at the numerous amounts of galleries containing images taken with the lenses that are being considered. Are the colours accurate? Is the saturation ok? What about contrast? Whilst these things can be adjusted in editing software it is best to get the most accurate before post image editing as there is only so much that can be done before the image starts looking artificial.

Try renting a version of the lenses that are being considered and take them out on a test run to see how they perform. During the testing it is important to see how each lens feels and make sure it sits right on the camera body. Does the lens feel nice and comfortable to use? Are the buttons, i.e. the auto focus/manual focus and the image stabilisation, easy to get to and operate? Whilst testing the lenses take plenty of images, after all digital images cost virtually nothing and you can always delete the really bad ones at no expense, for comparison purposes. Take images with the image stabilisation on and off, as well as at all the apertures and focal lengths. It is important to really put the lenses through their paces so be prepared to spend some time doing this.

Buying a Zoom lens can be a mind field and a painstaking task. It is a decision that should not be taken lightly and all photographers are well advised to spend some time researching and testing before making the final decision and making a costly mistake.