The job of a telephoto lens is to bring the image closer than that of the natural angle of view of the human eye. Having a magnifying effect is useful for shooting wildlife or sports shots where it is impossible to get physically close. There are also many other applications that Telephoto Lenses can be used, which will be outlined here.
A medium telephoto lens will prove to be a good investment and the most popular of these is the 70mm-200mm lens. This lens is a general-purpose telephoto that lives on my camera when doing environmental portraits. Although this lens will not bring your subject in incredibly close, it does afford a sensible working distance with your subject- without being in their face. These lenses will return a shallow depth of field and if shot with the aperture wide open they can isolate your subject nicely from the background. Telephoto lenses demand higher shutter speeds due to the nature that everything is magnified! That means that the slightest wobble will show up on your image as camera shake.
To avoid this happening you need to increase the shutter speed substantially. The 200mm lens would require at least a 1/250 of a second shutter speed to avoid showing shake. You can achieve this quite easily by increasing your ISO when working in aperture priority. As Telephoto Lenses are more susceptible to camera shake, a lot of manufacturers build them with some sort of image stabilisation device often refereed to as ‘IS – Image Stabilisation’ or ‘VR – Vibration Reduction’. This system allows us to handhold the camera at lower shutter speeds without the signs of visible shake. It is advisable to read the manufacturers manual to see what each lens is capable of.
Portrait photographers also like the effects of Telephoto Lenses as they flatten the features of the face making them look more flattering. Most portrait photographers favour between a 85mm to a 135mm. That being said, I have shot portraits using extreme focal lengths such as the example shot taken with a 420mm (300mm prime with x1.4 convertor). I love the shallow depth of field, which totally blurs any foreground and loses any detail present in the background.
As I said above, these lenses do have a flattening effect. This is all true for Landscapes or any other subject that you wish to shoot with a Telephoto Lens. It gives the appearance of shortening the foreground to the background, making hills appear closer together than they actually are. A great example of this is in the image below, shot from the window of a DCH-6 Twin Otter aircraft in the foothills of the Himalayas. It gives the impression that the hills are stacked up on each other. It’s a very cool and interesting effect that can be applied to a lot of different subjects.
Longer Telephoto Lenses become more of a specialist item, with the use becoming more limited than general. Couple this with the cost and you have to ask yourself how much use will you get from a 500mm lens? Unless you specialise in wildlife or sports photography and are making good money, then these lenses are best hired for that odd job.
As with all lenses you pay for what you get, but a good 70mm-200mm will earn its keep in no time. It is bound to be a go to lens, or if like myself, it could end up finding itself living on your camera for some considerable time. I find myself using the 70mm-200mm for a lot of landscapes, just isolating parts of the scene. I have also been known to use the 300mm when working in the field.
It’s very unlikely that you will use any filters with a telephoto lens as they simply do not lend themselves to the task. A polariser will drop your shutter speed right down, which is not what you want with this type of lens and it certainly won’t see grads. The only filter that I would recommend is a skylight or UV to protect the expensive front element. These lenses can also be a pretty hefty weight, so this is something to consider when travelling. If you plan to do a lot of travel then I recommend you do some research to find the best optical quality verses weight.