A Guide to Birding with Long Lenses

Capturing amazingly sharp photos of birds in the wild is the goal of many birders. There are different ways to do this, but the most organic is using extremely long telephoto lenses for digital or film SLR cameras or mirrorless interchangeable lens cameras. Not only useful for photography, modern digital cameras also can record video and sound to capture the flight of a bird and its song. The telephoto lens and camera may be your standard observing optic in the field and, not only that, the clarity and crispness of modern optics can help identify a rare species and then capture it photographically as proof of its location, or for further analysis and sharing.

In this third segment of a four-part series, we will discuss what to look for if you are looking to observe and capture birds with a camera, as opposed to straight optical viewing.

Another Way

The traditional birding optic is the binocular. Spotting scopes are also popular for closer views of birds in the wild. However, the popularity of bird photography, enhanced by the accessibility of digital photography, has led a new generation of birders (and converted more than a few veteran birders) to the possibilities presented by birding through a long telephoto lens. Bill Stewart, Director of Conservation and Community at the American Birding Association, says that the new generation of birders has really taken to the idea of long-lens birding and that many youngsters are showing up for nature walks “without optics; just cameras.” He has seen the trend explode in the past two to three years and says that the number of cameras on a given birding outing is always on the rise.

Eric Lind, the Audubon Constitution Marsh Center & Sanctuary’s Center Director in Garrison, New York, is quick to emphasize the social aspects of birding. Birding brings friends and family together, as everyone can observe and enjoy the beauty of nature through birding. Of course, you can hand your binoculars to the person standing next to you to observe a distant bird, or you can use a long telephoto lens and camera, take a photo of that bird, and then share it with the entire Internet-connected world on social media websites. Birding through cameras, and the ability to easily share captured images and video, has given a completely new and exciting dimension to birding.

What Magnification Power Is That Telephoto Lens?

Binoculars and spotting-scope magnification are presented in simple numbers. For instance, a pair of 8x40 binoculars has a magnification of 8x and a 40mm objective. An 80mm spotting scope has an 80mm objective and may come with a zoom eyepiece with a magnification of 20-60x.

Camera lenses are measured in focal length, not magnification. Focal length is the distance from the lens’s rear nodal point to the image plane inside the camera body. The greater the focal length, the greater the magnification of the lens will be. For example, a popular telephoto lens is the Nikon AF-S NIKKOR 300mm f/4E PF ED VR lens. The 300mm represents the focal length, not the objective diameter.

On the B&H Photo website, you will see magnification listed as a specification for camera lenses (the NIKKOR 300mm f/4 mentioned above has a magnification of 0.24x). This number is NOT the magnification we use to compare the camera lens to the birding binocular or scope—it is the reproduction magnification and is an important specification for close-focusing macro lenses.

Luckily for birders, it is very easy to convert the focal length of a camera lens into a binocular/scope-like magnification factor with simple math.

On a full-frame digital or 35mm film camera, 1x magnification is achieved by using a 50mm lens. Therefore, a 100mm lens is 2x, 200mm lens is 4x, etc. To get the optics magnification factor, simply divide the focal length of the lens by 50.

Formula

So, using the formula, we now know we need a 400mm lens to approximate the magnification of an 8x binocular and a 500mm lens to approximate a 10x binocular. And, if you are familiar with camera lenses, you probably know that lenses of those focal lengths are most definitely not inexpensive.

Even more extreme, if you want to simulate the magnification of a 20-60x spotting scope zoom eyepiece with your camera, you need a 1000mm lens for the “short” end and a 3000mm lens for the long end!

Telephoto Lenses

Camera lenses are not only measured by their focal length; the other primary specification is their maximum aperture. The aperture number is displayed as an f-stop and the number itself is a ratio of the diameter of the effective aperture to the focal length of the lens. Because we are dealing with a ratio, the smaller the number, the more light the lens allows in. In photography, light is everything. With a larger aperture, the lens will allow the photographer to take photos at faster shutter speeds, freezing the motion of a bird in flight, and the light-gathering capabilities of the larger lens will also allow the birder to photograph in less than ideal lighting conditions.

The drawbacks of the large-aperture telephoto lenses are weight and cost: bigger lenses are heavier and make your wallet lighter.

You do not need a large f/2.8 aperture super-telephoto lens to capture great photos of birds. There are other options. Many manufacturers make two versions of their super-telephoto lenses—one with a large f/2.8 aperture and one with a smaller f/4 or f/5.6 aperture. Depending on the focal length, the smaller-aperture versions can still be pricey, but they certainly cost less than their big brothers, and they are often considerably lighter, while providing optical quality similar to the larger lens, albeit with less light-gathering capabilities. Birding photographer Arthur Morris has virtually retired his binoculars and spotting scopes and now views birds almost exclusively through a DSLR coupled to a Canon EF 100-400mm f/4.5-5.6L IS II USM lens.

Deputy Director of Audubon North Carolina Walker Golder uses the discontinued Nikon AF-S NIKKOR 600mm f/4G ED VR lens on his Nikon DSLR to capture images of birds. This large lens, when coupled with the DX-format sensor, gives him the optical equivalent of an 18x binocular.

Also, many of today’s DSLR cameras come with kit lenses that extend out to 300mm (6x power). This is a great focal length for birding, but they usually have smaller apertures and will not give excellent performance in low light. But, for the size, weight, and cost, they are unbeatable.

Another value lens is the telephoto mirror lens. It works similarly to a mirrored reflecting telescope and packs extreme magnification into a relatively small and lightweight package. The disadvantages are that the optical quality may not be exemplary; the maximum aperture is usually several stops less than a traditional lens at that focal length, and the mirrors produce distinctive doughnut-shaped, out-of-focus highlights that not everyone enjoys, aesthetically. You can find mirror lenses for different cameras at B&H Photo with focal lengths ranging from 300mm to 800mm.

Support

Depending on the focal length of the lens with which you are birding, it may be critical to bring a camera support into the field with you. A tripod will give you maximum stability, but, for portability, weight savings, speed, and flexibility, a monopod might be your best choice for birding.

Spotting scopes nearly always require a tripod because of their extreme magnification capabilities, but long lenses are more akin to the magnification seen in binoculars and, therefore, can be used with a bit less stability.

Also, with the weight of a large telephoto lens, having a method to remove that load from your shoulders or back, as well as to stabilize the lens for extended viewing, a support, no matter how many legs it has, might be your new best friend in the field.

The Camera and Lens Can Help

If you are immersed in the digital photography world, you have undoubtedly heard banter debating the advantages and disadvantages of full-frame versus smaller-sensor cameras. Cameras with sensors smaller than that of a 35mm film frame have what is known as a “crop factor,” due to the fact that they are only capturing a part of the projected image circle.

On a camera with a smaller sensor, the birder gets to enjoy all of the benefits of the crop factor. With APS-C sized sensors, the lens focal length is effectively multiplied by 1.5x (1.6x with Canon). Therefore, a 300mm f/4 lens on an APS-C camera gives you the full-frame equivalent of a 450mm f/4 lens. In optical magnification terms, the image is similar to a 9x binocular instead of a 6x—quite a big difference, especially considering you are using the same lens. Arthur Morris’s Canon 100-400mm lens is effectively a 160-640mm lens on a Canon APS-C digital camera, a 3x-13x optics magnification versus a 2x-8x on a full-frame camera.

Walker Golder’s 600mm NIKKOR is, effectively, a 900mm f/4 lens on his Nikon APS-C DLSR and he sometimes uses a 1.4x Nikon AF-S Teleconverter TC-14E III to get out to an equivalent 1260mm on the DX camera. Working around Cape Hatteras, he is often observing and documenting nesting shore birds and migrating terns on their way to Arctic breeding grounds. He says, “It is nice to have that extra reach because shore birds and water birds are very sensitive to disturbances, sometimes with fatal consequences.” Migrating shore birds, he says, could be on a feeding stopover in the middle of an extremely long journey and disturbing them is counterproductive to birding and nature conservation efforts.

Just like with binoculars, the more magnification the lens provides the birder, the more the image is susceptible to vibration and image shake that will cause blurring of your photographs. The longer the focal length, the more difficult it is to steady the lens. Today, many telephoto lenses come with image stabilization systems that help counteract this movement. For birding, this feature will come in very handy, especially at greater focal lengths/magnifications. Some image stabilization systems must be shut down when the lens is tripod mounted, so check your owner’s manual before you mount such a lens.

Another thing a digital camera can help with is ISO. ISO is, basically, the sensitivity of the sensor to light. With film, you would buy a roll of film designated for a fixed ISO or ASA: 200, 400, 800, etc. With digital cameras, you can increase the digital equivalent of ISO to make your sensor more sensitive to light. This allows you to use a smaller-aperture telephoto lens, or shoot in darker conditions, while still maintaining sufficient shutter speed to counteract camera shake or motion blur and freeze motion from a bird in flight across your frame.

Teleconverters

An easy way to give your lens an extended reach while birding is by using a teleconverter. The teleconverter is a device that is mounted between the camera and lens that optically provides a specific factor of magnification for the lens. The most common teleconverters come in 1.4x and 2x magnifications. There are other magnifications to be found, including 1.7x and 3x. Also, unlike the crop factor gained from using smaller sensors, teleconverters will reduce the lens’s maximum available aperture—1 stop of light for a 1.4x teleconverter and 2 stops for a 2x teleconverter.

As an example, if you use a 2x teleconverter on a 300mm f/4 lens, the lens effectively becomes a 600mm f/8 lens. When compared to optics, the lens goes from 6x to 12x magnification, a nice gain, but less light will reach the sensor or film due to the smaller effective aperture. A 1.4x teleconverter on the same lens gives you a 420mm f/5.6 equivalent lens at an optical magnification of 8.4x.

There are additional drawbacks. The teleconverter adds optics to the light path between the camera and lens; therefore there is usually degradation in image quality due to the fact that the light is passing through more glass. Depending on the camera you are using, you may lose autofocus capabilities, even if the teleconverter supports autofocus functionality, due to the reduced aperture preventing enough light to allow the autofocus sensors to work properly. It is important to note that teleconverters are made by many lens companies and third-party manufacturers, span a broad price range, and have various options pertaining to electronic connectivity between the lens and the camera. Before buying a teleconverter, be sure to verify your lens’s compatibility with whichever device you are considering.

The Alternative

There is an alternative to the potent combination of a large lens and SLR camera: the “superzoom” point-and-shoot camera. Over the past few years, many camera companies have been producing point-and-shoot cameras with previously unheard-of telephoto capabilities. For example, the Nikon P1000 features an optical zoom lens that extends from 24mm to 3000mm. At the far end of the telephoto range, that is the equivalent of a 60x magnification spotting scope.

Patrick Comins, Director of Bird Conservation at the Audubon Society’s Connecticut office and President of the Friends of the Silvio O. Conte National Fish and Wildlife Refuge, has used cameras from the Canon SX series—today, the Canon SX70 HS. These days, armed with his superzooms, he admits that when on a walk, his “first instinct is to go for the camera” instead of his trusty binoculars. He says that, “If you want to shoot a [birding] magazine cover, you need a DLSR and telephoto lens,” but, when it comes to easy image sharing and observing, the superzoom has a great advantage. Just the other day, Comins spotted a Prothonotary Warbler in Connecticut, on a migratory overshoot. It is rare that they venture so far north. He immediately grabbed his SX60 for observing and imaging and never viewed the bird through is binoculars.

Do you have any tips for bird photography with long lenses? Share them with us in the Comments section.