Extended-range zoom lenses, popular telephoto ranges, teleconverters, and telephoto lens buying and shooting tips. By Margaret Brown.
Longer lenses magnify the scene, making subjects appear closer. They can provide a useful ‘working distance’ between you and your subject, and allow you to be more selective with your shots. However, magnification also increases the risk of camera shake.
Beyond a certain size (which varies with the photographer’s strength and experience) it can be difficult to shoot with the camera and lens hand-held, even in normal outdoor lighting. Most modern tele lenses provide at least two f/stops of built-in shake correction and some can combine it with in-camera stabilisation to provide much more.
Integrated stabilisation in the camera and lens enables even super-telephoto lenses to be used hand-held in normal lighting when both systems work together. (Source: OM Digital Solutions.)
Telephoto prime lenses are usually faster and let you shoot in lower light levels. They also provide more control over the zone of sharpness in the image; although fast primes are often quite heavy.
Telephoto lenses – especially those with longer focal lengths like the one shown here – are very popular with wildlife photographers, particularly birders. (Source: Camera House/iStock.)
Zoom lenses are popular as they are convenient and versatile to use. Many cheaper tele zooms have variable apertures that range from around f/4.5 at the widest to f/5.6 or f/6.3 at the long end of the range. You’ll pay more for a zoom with a constant maximum aperture that spans the entire zoom range – but it’ll be heavier because it has larger and heavier elements to let more light reach the sensor.
In this article we look at the special characteristics of telephoto lenses with focal lengths of 70mm or longer.
When you shoot with a narrow angle of view it causes subjects close to the camera to appear similar in size to objects much further from the photographer. This ‘compresses’ the perspective and makes them seem closer together than they really are.
This photograph shows the extreme perspective compression produced by a 750mm super-telephoto focal length. The two dinghies closest to the camera are in fact several metres apart, while the two smaller dinghies are at least 10-12 metres further back and the shoreline is more than 100 metres behind them.
Extended-range zoom lenses
Extended-range (or ‘all-in-one’) zoom lenses are popular with travellers and entry-level photographers because of their versatility and convenience. Early all-in-one zooms had relatively low zoom ratios of around 7x but today several manufacturers offer 10x (typically 24-240mm) zooms.
Having one lens that can be used for everything from landscapes and portraits through to sports and wildlife photography is both convenient and a lighter and cheaper way to start your camera kit. You seldom need to swap lenses, reducing the risk of dust entering the camera. You can also quickly re-frame a scene without shifting position.
Extended-range zoom lenses cover a range from wide angle (top picture) to long telephoto (bottom picture) with close focusing capabilities. Note: both pictures were shot from the same position.
On the downside, extended-range zooms are always slower than shorter zooms because they have relatively small maximum apertures. Many start at around f/3.5 at the ‘wide’ position and get as small as f/7.1 at full extension. Stabilisation is essential with these lenses.
While many are relatively sharp, they’re not as sharp as shorter zooms or prime lenses, especially towards the edges of the frame. They’re also prone to rectilinear distortion and vignetting (edge and corner darkening), although these flaws are generally corrected automatically in the camera when you shoot JPEGs.
Popular telephoto ranges
The most popular telephoto lenses cover diagonal angles of view from between about 34 degrees (70mm in 35mm format) to five degrees (around 500mm). True telephoto lenses can be split into three categories:
70mm–300mm: This category includes kit zooms, which are the cheapest option for a first purchase, particularly when they’re bundled with a camera. Most span a 70-200mm range, which includes portraits at its shorter end while still providing enough reach for some sports, action and wildlife photography.
A fast f/2.8 constant-aperture 70-200mm zoom lens was used to take this portrait of a powerful owl in dense forest cover. The 200mm focal length was needed to provide an adequate camera-to-subject distance that allowed time to record the shot before the bird flew off. The camera’s ISO setting was a relatively high ISO 800 to enable a fast 1/500 second shutter speed.
Kit zooms with variable apertures are usually slow (typically f/4.5-6.3). Most are made mainly from industrial plastic, which is tough and light in weight. They can provide an easy way to find out whether you want to invest in faster lenses and/or lenses with longer focal lengths.
Constant-aperture lenses with faster (f/2.8 or f/4) maximum apertures are popular with sports and wildlife photographers (including birders who work from hides), especially if the lens is on a high resolution camera that provides scope for frame cropping. Expect to pay at least 30% more for a one-stop (f/4 to f/2.8) lens speed advantage.
200mm–500mm: This range of focal lengths is good for photographing wildlife, sports photography and other situations where you require greater magnification. Stabilisation is essential in these lenses if you want to use them hand-held, even with faster lenses.
Some super-telephoto lenses can be used for shooting close-ups as they provide relatively long working distances with high magnification. Background bokeh (rendition of out-of-focus areas) is often very attractive with these lenses.
Most people can hand hold at least 200mm reasonably well and in-lens IS systems can usually provide two or more f-stops of camera shake correction, depending on your shooting technique. Watch your shutter speeds when shooting with higher magnifications and stay within the range where you know you can keep the camera steady.
300mm and higher: Telephoto lenses with focal lengths longer than 300mm fit into the super telephoto category. These lenses offer the most extreme magnification and the greatest perspective compression.
Unfortunately, such narrow fields of view can make it difficult to capture moving subjects and they require a lot more stabilisation when used hand-held. Don’t rely on filling the frame with the subject with your longest lens when photographing birds in flight. If the bird fills even half the frame, keeping it in frame and in focus is extremely difficult at 500mm and requires a lot of practice.
Teleconverters can be an affordable way to extend the effective focal length of a lens and a number of recent tele lenses come with built-in teleconverters containing a group of elements that can be switched in when you want extra reach. With a 1.4x teleconverter, a 400mm lens has an effective focal length of 560mm, while a 2x teleconverter effectively doubles its focal length to 800mm.
Super-telephoto lenses sometimes come with built-in teleconverters that can extend the zoom range while keeping the lens compact and manoeuvrable. Built-in stabilisation in the lens and the camera body can provide up to eight shutter speed steps of shake correction for handheld shooting. (Source: OM Digital Solutions.)
Unfortunately, teleconverters also reduce the light intensity by the converter’s factor. A 1.4x converter teleconverter cuts the light by one stop, while a 2x converter reduces it by two stops. This light loss can create difficulties for the camera’s autofocus system and it may also degrade image quality.
Be cautious about using a third-party converter (one not made by the lens or camera manufacturer) as it may not pass some vital electrical signals between the camera and the lens, which could mean autofocusing doesn’t work at all. Finally, check that your lens is suitable for use with a teleconverter because they aren’t suitable for lenses with maximum apertures less than f/4.
Choosing telephoto lenses
Your choice of telephoto lenses should be based on three considerations:
1. How much you’re prepared to pay.
2. The kinds of subjects you want to photograph.
3. How much weight you are prepared to carry.
A tight budget will constrain your other choices so you should focus on point 2 and decide the focal lengths you should consider. Point 3 will be largely irrelevant since you won’t be able to afford the heavier lenses.
If price is not an issue, Point 2 should be your focus so you should consider focal length and lens speed. You’ll need longer focal lengths for sports and wildlife, while shorter focal lengths work better for intimate portraits of humans or animals.
A moderately fast (f/4) maximum aperture on the 200mm telephoto lens used for this shot of a female fairy wren provided nice background blurring plus a good separation of the subject from the background.
Fast lenses are best for low light work. They also make it easier to isolate subjects from their backgrounds – but beware of very narrow planes of focus that can produce unnatural-looking images when using super-telephoto lenses.
The longer and faster your lens, the heavier and more expensive it will be. Lens weight is important when you have to carry your kit on long hikes, especially over difficult terrain. If you’re shooting from a vehicle, it’s largely irrelevant.
Aim to match the lens size and weight to the size and weight of your camera to ensure the balance is easy to handle. Older DSLR tele lenses fitted to modern cameras via an adapter may be difficult to balance on smaller, lighter mirrorless bodies.
Unstabilised lenses can normally be used hand-held at shutter speeds that are the reciprocal of the lens focal length. If you shoot at 200mm, the shutter speed should be 1/200 second or faster – for a given ISO setting. With a 400mm lens, the minimum shutter speed is 1/400 second – and so on.
A telephoto lens is great for capturing photos of animals in the wild or in zoos and game reserves. Stabilisation lets you shoot with the camera and lens hand-held, even in relatively low light levels, such as twilight, as shown in this image, which was taken with a stabilised 300mm lens at f/7.1 and a high ISO setting of 1250.
Autofocusing systems may become sluggish or inconsistent in dim lighting and you may not notice any degradation until you check your shots on a computer and discover many of them are a little soft. Be prepared; switch in image stabilisation or increase the camera’s ISO value. Two stops of IS lets you shoot at 1/50 second with a 200mm lens or 1/100 second with a 400mm lens.
Putting the camera on a gimbal can improve steadiness when shooting video, while a monopod can offer extra support by reducing the risk of up/down movement. Tripods are essential for astrophotography as well as when shooting time-lapse sequences and any other modes that combine multiple image frames recorded over a period of time.
Pros and cons of teleconverters
This article by Margaret Brown is an excerpt from Lenses 2nd Edn pocket guide
Pocket guide Partner: Camera House