The telephoto lens is the one that draws everyone's attention to the photographer. It makes your camera look so much more impressive than a 50mm f/1.8 lens. Canon has done a great job of promoting theirs by making their most desirable telephoto lenses an off-white color. These are the ones you see under every NBA basketball goal and at all major sporting events.
But, aside from the general admiration they will draw to your camera and, hence, to your, the photographer, there are some compelling reasons that having a good telephoto lens is beneficial to every digital SLR camera owner.
What constitutes a telephoto lens?
A telephoto lens is any lens that is longer than a "normal" focal length (30mm-50mm). The angle of view is much narrower than that of a wide-angle or normal lens. Such a lens will magnify the subject of the image as compared to what a person can see with the naked eye, but it does so without distorting the image.
Construction of a telephoto lens uses a group of lens glass that is arranged to increase the size of the image on the camera's image sensor. There are medium telephoto lenses which are between about 70mm and 200mm in focal length, and there are super telephoto lenses which have focal lengths of 300mm and beyond.
Telephoto Lens applications
There are some types of photography that are naturally suited to the use of telephoto lens. These are images that are taken when the subject is quite a distance away from the camera, and they include the aforementioned sports photography category, wildlife imagery, travel photos when it is not possible to get close to the subject of interest, and some types of close-up photography.
One application of longer focal length lenses that is becoming more popular these days is in the area of landscape photos. It is possible to get some very creative shots by using long length lenses rather than the more common wide-angle lenses for landscapes.
Getting a sharp image with a Telephoto Lens
Taking pictures with super long focal lengths has some issues that must be addressed in order to get really good image quality. Typically, with longer focal lengths, any camera movement is exaggerated, thus creating a blurry image. Basically this means that the lens must be stabilized. This can happen simply by using a tripod, but it can also be accomplished in the lens software. Engineers have devised a way to include image stabilization (Nikon calls it vibration reduction) right in the lens. With this feature, you can take pictures much easier without the treat of blur even at slower shutter speeds.
Another way to get sharper pictures is to get a lens that has a very wide aperture. Some longer focal length lenses have an aperture as wide as f/2.8, and some of those even come with image stabilization built in. Both Nikon and Canon have 70-200mm lenses with stabilization. Of course, this advanced feature does not come without added expense. However, if your goal is to hand-hold your camera, it could be well worth the investment.
Telephoto Lens for Portraits
While wildlife and sports are the more visible and well-known uses for these special lenses, many photographers use telephoto lenses for portraits. There are two excellent reasons for using them in portraits.
First, a long length lens creates a nice blurry background while keeping your subject in sharp focus. This blurry background, known as bokeh to those in photography circles, is very desirable in portraits. In fact, it is the one feature by which all portrait lenses are judged. By their very nature, long length lenses are really good at blurry backgrounds.The second reason is perspective. A subject looks much more natural when the photographer can step back at least ten feet to get the portrait shot.
The most popular focal length for portrait photography is 85mm. Portrait photographers usually use a single focal length lens for their work, however, some photographers are using 70-200mm zoom lenses with great satisfaction. In either case, the lenses of choice have a very wide aperture.
Telephoto Lens choices
Those who are just getting started with digital SLR photography will most likely start with a medium telephoto lens. Both Nikon and Canon sell a "starter" zoom lens equal to 55-250mm with image stabilization. These are excellent and inexpensive. Canon and Nikon also have a similar lens choice at 70-200mm with f/2.8 aperture and image stabilization that is probably the most popular medium length lens available on the market.
Longer length lenses are primarily for professionals and photo enthusiasts who have a very specific need, such as wildlife or sports. Lenses with focal lengths of 300mm and longer are quite costly, in fact they generally cost more than the camera they are attached to. The addition of a telephoto lens to your camera bag will truly expand your photography repertoire, and if it is a zoom lens, you will get even more use from it.