A telephoto lens is a type of camera lens designed for taking photographs of subjects at moderate to far distances. Also known as a "tele lens" or "long lens", they are a type of long-focus lens which use a special internal construction to give them a focal length much longer than the length of the lens itself. This makes them smaller, lighter, and easier to handle, while still giving excellent long-range capabilities.
Telephoto lenses are commonly used when photographing sports events, wildlife, and in any other circumstances where the photographer can't get close to the subject. They are also popular in portrait and macro photography as they produce a pleasing, natural perspective free from the distortion caused by using a wide-angle lens.
Focal Length
Telephoto camera lenses come in both "prime" (fixed focal length) and zoom varieties. Those with fixed focal lengths tend to be of higher quality, although zoom lenses offer the obvious advantage of greater flexibility.
Telephoto lenses are available in moderate to extremely long focal lengths.
Focal lengths typically start at around 85mm and extend up to 800mm and beyond. Longer focal lengths are able to capture more distant detail, but are also more expensive, bigger, and heavier.
Because of the huge variation in focal lengths, tele lenses can be grouped into three types:
Short Telephoto Lenses (85mm - 135mm)
These are ideal for shooting portraits and candid shots (for example at weddings), where you are quite close to the subject but don't want to intrude too much. They are compact and lightweight, and can be hand held for fast shooting.
Medium Telephoto Lenses (135mm - 300mm)
These lenses are popular with sports and action photographers who can get quite close to the action, for example standing on the sidelines. For this type of photography, aperture is critical in minimising blur, particularly when photographing fast-moving subjects.
Super Telephoto Lenses (300mm+)
Most amateur photographers will not need a telephoto lens with such a long focal length, but they are a popular choice among professional wildlife and nature photographers, as well as sports photographers who can't get very close to the action (e.g. motorsport photographers).
The longest lenses have telescope-like magnification, making them great for astrophotography, although they can be extremely expensive.
Focal Length Choice
Your choice of focal length depends mostly on the subjects you intend to shoot. If you are just getting started with telephoto photography, and want to experiment, then a telephoto zoom lens is a good choice. Although these don't produce such high-quality images as a prime telephoto lens, they allow you to experiment with a range of focal lengths.
| 85mm - 135mm | 135mm - 300mm | 300mm+ | |
|---|---|---|---|
| Price | Cheapest | Mid-range | Most expensive |
| Weight | Lightest | Medium | Heaviest |
| Size | Smallest | Medium | Largest |
| Working Distance | Close to medium | Medium to far | Far to very far |
| Subjects | Portraits | Close sports and action | Far sports, wildlife, nature, astro |
Depth of Field
With all camera lenses, a longer focal length means a narrower depth of field, and telephoto lenses are no different. Particularly with longer telephotos, it can be difficult to get your focusing spot on, and even a slight change in camera position can cause blurriness. Because of this, you should put your camera on a tripod when using anything but the shortest telephoto lens.
Aperture
If you intend to shoot fast-moving subjects like motor racing or sports events, then you'll need a wide maximum aperture to help you achieve a fast enough shutter speed to avoid blurring. This is also important if you intend to hand-hold your camera.
As focal length increases, lenses with wide apertures get more and more expensive. If your ideal lens is out of your price range, consider whether you could live with a shorter focal length, or use a tripod and longer exposure time.
Perspective Compression
Because of its long focal length and narrow field of view, a telephoto lens makes near and distant objects seem closer together and more similar in size than they appear in real life. This effect is known as "foreshortening" or "perspective compression".
A telephoto lens makes distant objects appear much larger. Image by Brenda Anderson.
Foreshortening makes for very flattering portraits, as facial features look natural and in proportion, and don't exhibit any of the bulging and distortion that appears when shooting close up with a wider angled lens. Foreshortening can also be used to give more emphasis to distant objects, for example by making the moon appear much larger in the night sky.
Lens Construction
Telephoto lenses use a special construction to achieve a focal length greater than their physical length. There are two different ways of doing this:
Refractive Lenses
Refractive telephoto lenses, also known as "negative" lenses, use two lens groups (known as "lens elements"). The first element bends the light inwards, and the second element straightens it out again before it hits the film or sensor. This has the effect of shortening the distance the light must travel, while still ensuring it hits the sensor at the correct angle.
Mirror Lenses
A mirror lens, also known as a "reflex lens" or "catadioptric lens", uses mirrors rather than lenses to alter the path of light. The light enters through the front lens as normal, but is then reflected back on itself by a curved mirror. The light then hits a second mirror on the back of the front lens, which bounces it back towards the sensor.
Refractive or Mirror?
Refractive lenses produce a much higher-quality image than mirror lenses, with better sharpness and contrast, and more pleasing background blur. If you can afford this type of lens, it is a much better overall choice.
The main benefits of mirror lenses are that they are smaller, lighter, and cheaper. However, they suffer from inferior picture quality, and have a fixed aperture which can limit their usefulness. They should really only be considered if you are on a tight budget, and even then you'd probably be better off saving up for a bit longer to buy a refractive lens.
Supporting a Telephoto Lens
Short focal length telephoto lenses can generally be hand held without any noticeable blurring from camera shake. This is particularly convenient when photographing portraits or taking candid shots, where you have to react quickly.
When hand holding your camera, use the fastest shutter speed you can. A good rule of thumb is to use a shutter speed that at least matches your focal length - for example, when using a 200mm lens, you should use a shutter speed of 1/200th or faster.
Telephoto lenses with longer focal lengths are easily affected by camera shake due to their extreme magnification factor. Their narrow depth of field makes focusing difficult, and long lenses with a narrow maximum aperture may not be able to reach the shutter speeds required for hand holding. They also tend to be heavy, making them uncomfortable to hold for long periods of time. When using longer lenses, you should use a tripod or monopod to keep your photos sharp and to take the strain off your arms.
Buying a Telephoto Lens
Quality varies greatly in the telephoto lens market. Unless you are on a very tight budget or are just looking to experiment, avoid mirror lenses in favour of superior refractive lenses.
When buying a telephoto lens, you generally get what you pay for. Try to stick to reputable brands like Canon, Nikon (Nikkor), Sigma, Tokina, and Tamron. If you can't quite afford your ideal lens, it's often better to wait rather than buying a cheaper equivalent which turns out to be inferior.
Check online reviews and ask around on forums to get opinions and recommendations on specific models, and then shop around to find a good price. Online stores such as Amazon and Adorama usually offer the best deals.
Cover image by Doo Ho Kim.
