10/12/2014
Introduction to Super-Telephoto Lenses
Bristling along the sidelines of practically every professional sporting event, super-telephoto lenses are known for their ability to reach out and capture distant subjects with exceptional clarity and speed. They feel incredible in the hand, with top-of-the-line build quality and a heft that gives shooters confidence in their equipment. And, many feature a variety of switches and buttons that allow users to set up the lens for optimal performance in any situation.
In addition to length, these lenses feature all of the latest technology, such as advanced optical construction, accurate image stabilization, and exceptionally quick autofocus motors. Super telephotos sit at the top of their respective lens lineups because of this assortment of features and capabilities, and being packed with the latest tech ensures that any investment is well worth it.
Focal Length
The most important feature of these lenses will always be the focal length. The ability to photograph and record images from an extremely long distance cannot be understated, especially when dealing with subject matter that is inaccessible, easily spooked, or both. The most common use for lenses greater than 300mm would be sports and wildlife, where photographers are prevented from getting close to their subjects.
Prime lenses tend to dominate in terms of quality and length, with Canonâs and Nikonâs current longest offerings sitting at 800mm, though each has released a 1,200mm model in very limited quantities. This compares to the longest zoom lenses available from these two manufacturers only reaching 400mm. Third-party lens manufacturers have been jumping into the super-telephoto game lately with their own offerings, such as Sigmaâs 150-600mm, 200-500mm, and 300-800mm lenses, which provide more versatility but in a less compact package.
Canon EF 100-400mm f/4.5-5.6L IS II USM Lens
Going down the line, Canon and Nikon feature options at the 600mm, 500mm, 400mm, and 300mm focal lengths, and Sony jumps in with 500mm and 300mm A-mount lenses. Sigma also has a few lenses for a variety of different mounts at 800mm, 500mm, and 300mm. And, for more variety, some companies offer multiple options at each focal length so that users have a selection of items that are more portable or affordable.
Sony 500mm f/4.0 G Telephoto Prime Lens
The next thing to consider is sensor size, especially since APS-C cameras come with inherent crop factors that will extend the equivalent focal length. Pentax uses APS-C sensors solely, which gives them the advantage of not requiring lenses as long to achieve the same effective reach. For example, the company's longest lens is only 560mm, which is equivalent to 840mm in 35mm format. This crop factor makes cameras like the 7D Mark II incredibly useful for sports and wildlife shooters, since they can enjoy more reach, yet pack somewhat more lightly.
Zooms offer the added benefit of versatility, something that can be vital to some shooters who require speed and canât afford to keep swapping out different lenses. Lenses like the Canon EF 200-400mm f/4L IS USM provide a very usable focal range along with the added feature of a built-in 1.4x teleconverter, which will boost the focal length to 280-560mm at the cost of one stop of light. However, zooms have generally been limited to about 600mm, with the exception being the Sigma 300-800mm lens.
Sigma 300-800mm f/5.6 EX DG APO IF HSM Autofocus Lens for Nikon AF-D
Aperture
The second most important feature of any lens is the aperture. With super telephotos, you will find that extremely fast apertures arenât as common, and that the fastest options are also significantly larger and more expensive than the more conservative models. If we look at Canonâs 400mm lenses, we will find an f/2.8, an f/4 DO, and an f/5.6. Comparing just the size and weight of these models, we can see the f/2.8 lens is more than double the weight and almost twice as wide. If quality is all that matters, then the f/2.8 would appear to be the better option; however, one must consider their needs and decide whether it is worth taking a hike with an 8-lb or a 3-lb lens.
Most extreme telephotos will sport an aperture closer to f/5.6, which is the limit for most modern-day autofocus systems (some do offer limited shooting at f/8). This is mostly due to size: an 800mm lens with an f/2.8 aperture would be impractical for the everyday shooter and would not be easy to transport.
Faster apertures do have a couple of key benefits that are worth mentioning. Primarily more light will be reaching the sensor, enabling faster shutter speeds and lower ISOs for better images and overall quality. This will also improve AF speed and performance, as the sensor can better âseeâ what is happening in the scene. Next, there will be more separation between your subject and the background, due to shallower depth of field.
Zoom lenses will usually feature variable apertures, which keeps overall lens size down, though some do manage to maintain a constant aperture. These options are generally slower than their prime-lens counterparts, but can still be useful in a variety of situations, especially considering the ISO ranges possible on the latest digital cameras.
Image Stabilization
Elaborate image stabilization is almost necessary when attempting to handhold lenses at these focal lengths. The reasons for this are that the longer lengths show more camera shake, and the heft of these lenses makes it exponentially more difficult to handhold, which is why they are often found mounted on a monopod. Modern day advancements from Nikon, Canon, and some third-party manufacturers are rated for approximately four stops of compensation, exceptionally useful when trying to shoot handheld. In-body stabilization from some manufacturers, such as Sony, does replace the need for optical stabilization and can allow the use of adapted telephoto lenses without losing this critical technology.
Another of the benefits found in super telephotos are the multiple IS modes available. Usually there are specific settings for panning and general handheld shooting. This allows shooters, like those working on monopods at a sporting event, to track horizontal motion more easily in the scene and capture it. A side benefit to image stabilization is that it will usually stabilize your viewfinder as well as your final image. This makes composition much easier, since the image you see wonât be jittery and shaking.
Autofocus
Focusing quickly and efficiently is a priority with super-telephoto lenses, especially due to their use in action and sports photography. While much of this is reliant on the camera and user, the inclusion of a supersonic or ultrasonic motor does a lot to ensure speedy, quiet focusing. These lenses also benefit from the inclusion of multiple settings on the physical lens, such as a focus limiter that will focus on subjects within a certain range or from a specific distance and farther. This means that the camera will not waste time hunting throughout the long focus range of the lens.
Other features include an AF lock button that will stop focusing so that users can prepare for a certain shot or position. Also, focus presets can be available on certain lenses to automatically return the focus distance to a specific setting. Additionally, these lenses will generally have a manual override option that will assist in fine-tuning focus.
Optical Technologies
Nearly every piece of optical technology is utilized in super-telephoto lenses, from nano coatings to prevent flaring to fluorite elements that control aberrations. Most common are extra-low dispersion elements, which can be available in other varieties, such as ultra low. These work with other elements, like fluorite glass and, to a lesser extent, aspherical, to produce the sharpest, most detailed images possible by reducing visible aberrations and correcting for distortion.
Diffractive optics can be found in some of Canonâs offerings and are able to dramatically decrease the size of a lens without compromising on image quality. The Canon EF 400mm f/4 DO IS II USM is the latest such example and will even reduce the amount of chromatic aberration visible in the final image, due to the dispersion characteristics of the diffractive element.
Anti-reflective coatings are found on nearly all lenses nowadays, and super telephotos are no exception. Each manufacturer has its own version, such as Canonâs Super Spectra Coating, Nikonâs Nano Crystal Coat, and Sonyâs Nano AR Coating. These coatings help eliminate flare and ghosting by reducing internal reflections. Also, many super telephotos have an additional fluorine or water- and dust-repellent coating on the front and rear elements that will allow users to clean their lenses easily when water and oil come in contact with the glass.
Filtration can be a challenge for these lenses, as most have front elements much larger than your standard screw-on options. These lenses accomplish this through the use of drop-in type filters. These fit into dedicated holders found near the rear of the lens and keep filter size significantly smaller than would be needed with front-mounted filters.
Construction
As they stand at the top of their lens lineups, these lenses are built to the highest standards, using materials like magnesium alloy to increase strength and keep the lenses lightweight. In addition to this, they are weather-sealed to ensure that the lens will keep functioning even when out on the field during a rainstorm, or while trekking through a rainforest on a search for an elusive creature.
Now, one common question is why many super-telephoto lenses are white. The explanation is simple: since these lenses are so large and are constantly being used in the great outdoors, they have a surface area that absorbs heat from the sun. The use of a white finish on the lens barrel reflects some of the sunâs energy and reduces the chances that any critical elements or parts will expand due to heat and throw things out of alignment during shooting. The actual amount of heat gain varies and, with the durable build quality of these lenses, users of black lenses shouldnât worry about it.
Teleconverters
Many super-telephoto lenses are compatible with teleconverters to further extend their reach. These will magnify the image by 1.4 or 2x without sacrificing important features like autofocus or image stabilization. This additional reach does cost one or two stops, depending on the magnification of the teleconverter. Compatibility can also be an issue for some lenses and cameras, as teleconverters have a glass element that can come into contact with the rear element of some lenses. Also, with a loss of light, some camerasâ AF systems may stop functioning.
Canon Extender EF 1.4X III
Alternative Lens Options
Many photographers will find that these lenses fall well outside their personal budgets and needs, but this doesnât mean that they should be left out of the super-telephoto world. Many budget options are available, though without the plethora of features and abilities of their more famous big brothers.
Catadioptric lenses, also known as mirror or reflex lenses, are one of these options. They utilize mirrors in their optical mechanics and are able to employ designs that are much shorter than standard optics. However, because of this design they cannot have an adjustable aperture diaphragm, so the aperture is fixed. Also, the use of a central obstruction produces doughnut-shaped blur, or bokeh.
Rokinon 500mm f/6.3 Mirror T-Mount Lens
There are some standard super telephotos and zooms available without the corrective optics and fancy optical designs that make lenses sharper and more compact. These lenses also usually are fairly slow and have all-manual controls. They are generally quite long due to the lengthy focal lengths of super telephotos. But, if you canât afford the latest and greatest or are simply looking for an entryway to super telephotos, any lens is better than no lens at all!
Read about the current crop of super-telephoto lenses, at B&H.com
