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. 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 their 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 longer 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 the longest offerings currently available being a few 800mm primes, although there have been even longer focal lengths available in the past. This compares to zoom lenses, which tend to top out around 600mm at their longest reach. While primes can be longer and certainly faster, zooms do offer greater flexibility to cover a huge array of super-tele focal lengths within a single lens.

The next thing to consider is sensor size, especially since APS-C and Micro Four Thirds cameras come with inherent crop factors that will effectively extend the equivalent focal length. This makes these smaller sensor cameras incredibly useful for sports and wildlife shooters, since they can enjoy more reach and pack somewhat more lightly.

Aperture

The second most important feature of any lens is the aperture. With super-telephotos, you will find that extremely fast apertures aren’t as common, and that the fastest options are also significantly larger and more expensive than the more conservative, slower models. If we look at 400mm lenses, we might find f/2.8 and f/4 options. Comparing just the size and weight, we can see an f/2.8 lens is significantly larger and heavier than an f/4 version. If quality and speed are all that matter, then the f/2.8 would appear to be the better option; however, one must consider one’s needs and decide whether it is worth taking a hike with the larger lens.

Zoom lenses will usually feature variable apertures, which keeps overall lens size down, though some do manage to maintain a constant maximum 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.

As focal lengths increase, so do the relative maximum apertures. Much of this has to do with size and practicality: an 800mm f/2.8 lens would be so large and heavy that it would be unrealistic for someone to carry, let alone mount on a tripod and use. Despite the impracticality of larger apertures on longer lenses, it’s still a balancing game, for many applications, between speed and size/weight of a lens. Especially with something like a 300mm lens, where you have choices to make between an f/2.8 or an f/4 or even an f/5.6, you should consider the shutter speed and ISO advantages of the faster lens, as well as the improved control over depth of field.

Differing from primes, it’s also worth noting that zooms have the advantage, or consequence, depending on how you look at it, of using a variable maximum aperture. It’s common to see tele-zooms with an f/4.5-6.3 or so maximum aperture, meaning that it can open up to f/4.5 at the widest focal length and only f/6.3 at the longest focal length. The benefit of this is reduced weight and a smaller form factor; the downside is, of course, the slower design. Zooms with constant maximum apertures, on the other hand, have the same maximum aperture throughout the zoom range but are noticeably heavier than variable maximum aperture lenses.

Image Stabilization

Image stabilization (IS) 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 them exponentially more difficult to handhold, which is why they are often found mounted on a monopod or tripod. Today's lenses are rated for several stops of compensation, which is exceptionally useful when trying to shoot handheld.

Another of the benefits found in super-telephotos is 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 IS is that it will usually stabilize your viewfinder, as well as your final image. This makes composition much easier, since the image you see won’t be jittery and shaking.

One other consideration to be mindful of is the increasing popularity of in-body image stabilization (IBIS), which opens up the possibility to use older, non-stabilized lenses more effectively and lessens the need for manufacturers to have IS in all of their lenses. Or, on the other hand, IBIS can often be used in conjunction with lens-based IS for even more effective stabilization in a wide variety of shooting situations.

Autofocus

Focusing quickly and efficiently is a priority with super-telephoto lenses, especially relating 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 work with other elements, like fluorite and, to a lesser extent, aspherical, to produce the sharpest, most detailed images possible by reducing visible aberrations and correcting for distortion. Beyond just improving image quality, Diffractive Optics or Phase Fresnel lenses (depending on the manufacturer) are used to reduce the overall size and weight of the lens while also reducing various aberrations.

Anti-reflective coatings are found on nearly all lenses nowadays, and super-telephotos are no exception. 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 or 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. Adding filters to the lenses is, instead, accomplished through the use of drop-in type filters that fit into dedicated holders found near the rear of the lens, which keeps 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 in the field during a rainstorm, or while trekking through a rainforest on a search for an elusive creature.

Now, one common question is, “Why are so many super-telephoto lenses white?” The explanation is simple: since these lenses have a larger surface area and are constantly being used in the great outdoors, a white finish on the lens barrel reflects some of the sunlight and reduces the chances that any critical elements or parts will expand due to heat and throw things out of alignment during shooting. Realistically, however, the actual amount of heat gain is probably negligible, and, with the durable build quality of these lenses, users of black lenses shouldn’t worry about it.

Teleconverters

Many super-telephoto lenses are compatible with teleconverters to further extend their reach. These will magnify the focal length by 1.4, 1.7, or 2x without sacrificing important features like autofocus or IS. This additional reach does cost one to 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 cameras’ AF systems may not be able to function.

Alternative Lens Options

Many photographers will find that these lenses fall well outside their personal budgets and needs, but this doesn’t 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.

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 tend to be a bit slower and have all-manual controls but, if you can’t afford the latest and greatest or are simply looking for an entryway to super-telephotos, any lens is better than no lens at all!

Are you a fan of super-telephotos? Which one(s) do you carry, and what features do you look for when purchasing one? Share your thoughts in the Comments section, below.