It has been a while since I have written about the technical aspects of photography and I thought it would be good to dive into a discussion about the broad field of wildlife photography. It is a big subject so I'll cover it in two separate postings.
I moved to Jackson, Wyoming last year primarily to be closer to nature and to the amazing wildlife in this part of the country. As a 'nature photographer,' I enjoy all aspects of outdoor photography from landscapes to wildlife to macro-photography, but it is wildlife that really gets me excited. When I write about wildlife photography I really mean WILD-life - not pets, zoo animals, or critters in cages of any sort, but real wildlife out in the open, fending for themselves. I like all sorts of wildlife from large carnivores to birds, grazers, cute little rodents, insects and other invertebrates and each of these families of critters bring different challenges to the photographer.
There are really three 'styles' of wildlife photography and each has its individual rewards. First, and most common, are wildlife portraits. You find a great animal out in a natural setting and are close enough to capture its image close up. Second, there are the beautiful scenic shots (below) with a magnificent animal in the foreground. Third, are the behavioral shots (see blog cover photo)when the critter you have found is doing its thing in an animated and interesting manner. The preparation and gear required to capture each of these styles of images is modified by the physical size of the animal you are shooting.
It goes without saying that a quality digital single-lens reflex (dSLR) camera body is the choice of most wildlife photographers but that doesn't mean that you can't capture great images with a super-zoom or even a point and shoot camera. I remember a few months ago staking out a black bear in Yellowstone for over two hours. I had a 600mm super-telephoto lens mounted on a sturdy tripod ready to go but the bear stayed in the bushes always partially concealed from my view. I packed up ready to move on when the bear took off across the road in front of a car giving the woman in the car a better shot with her phone camera in 20 seconds than I had in hours that cold Yellowstone morning. But good photography requires more than luck - you want to be able to capture good images, reliably, under many conditions. The dSLR is the best choice.
The next issue is the selection of lenses that will give your camera the best image. Wildlife photographers are always looking for the "big glass" but there are two types of 'big' that you must consider. Many times when photographing wildlife you cannot get as close as you would like to be - either because the subject will leave your field of view or the subject is bigger than the photographer and, therefore, demands space. So big lenses are usually part of every wildlife photographer's arsenal but how big is necessary? The answer is, it depends.
Many (most?) times you will want to 'fill the frame' with your subject. So the smaller the subject the closer you must be or the larger your lens must be. Generally, most start with a moderate telephoto lens in the 200-300 mm focal length range. These lenses are small enough and light enough to carry for a significant distance and yet will give a significant 'reach' to your subject. If you are using a crop sensor, rather than a full frame sensor, camera you will see even a smaller angle of view giving the appearance of more magnification. Typically, most APS-C size sensors have a 'crop factor' of 1.5x or 1.6x thus increasing the effective focal length of your lens by the crop factor. Effectively, you get more bang for your buck using a telephoto lens on a crop sensor camera body.
Another way to extend the reach of your lens is by adding a tele-converter (sometimes called a tele-extender) between the lens and camera. These converters increase the effective focal length of the telephoto lens that is attached by a factor of 1.4x or 2x. Doing the math, you can see that a 200 mm telephoto lens on a 1.6x crop sensor and a 1.4x teleconverter give you an effective focal length of 448 mm (200 x 1.6 x 1.4). A 2x tele-converter would increase the effective focal length even more to 640 mm. The increased effective focal length with a converter comes with a significant cost - reduced light to the sensor. A 1.4x converter reduces the maximum aperture of the lens by 1 stop and the 2x converter reduces it by 2 stops. This raises the second requirement for wildlife lenses - they must be 'fast.'
Generally, the best shooting of wildlife is in early morning and late afternoon as the sun is rising or setting. This means a high likelihood of shooting in low light situations. Low light means you will need a large aperture, long shutter speed, or high ISO for proper exposure. (See the Exposure Triangle, 2/21/13, and Where to Start with Exposure, 2/27/13 blog posts.) A long shutter speed is almost never a good option using a telephoto lens because of the chance of image blur due to 'camera shake' or movement of the subject. The rule of thumb is that the shutter speed should equal or be faster than 1 / effective focal length. So your 200mm lens on a crop sensor camera with a 1.4x converter means your slowest shutter speed should be 1/640 seconds or more practically, 1/1000th second. That is fast enough to eliminate blur from camera shake and to freeze (slow) movement of your subject but how do you get enough light to the sensor? The answer is a large aperture. So the second 'big' in wildlife lenses is a large diameter aperture - ideally f/4 or larger. The large aperture allows more light to reach the sensor in the time the shutter is open. Unfortunately, a large aperture is the major cost of a lens - more glass equals more money.
We will address the last of the exposure issues and other ways to improve your wildlife photography in the next posting. Until then happy shooting.