In Part 1 of this post, I discussed basic styles of wildlife photography, camera and lens options, and two elements of exposure. In this section I want to complete exposure considerations and address composition in wildlife photography.
We know when photographing animals, a high shutter speed is usually necessary to avoid motion blur due to movement of the subject or camera shake. We also know that to obtain a high shutter speed we need to open the aperture to allow more light to reach the sensor. But what do we do in the early morning and late afternoon when there is less available light and we are unable to get an adequate exposure at a high shutter speed? The last element of the exposure triangle is ISO or the sensitivity of the sensor to light. ISO is similar to the ASA rating of film - the higher the ASA, the more sensitive to light. The downside of higher ASA film is graininess of the image; the downside of higher ISO is the induction of digital noise into the image.
Digital camera sensors create an image in response to light turning on photo-sensitive pixels in the sensor. A small number of the millions of pixels in the modern sensor can 'discharge' spontaneously. Normally, these spontaneous pixel activations go un-noticed but when the image is under-exposed many more of the spontaneous activations are present for every intended light-activation of pixels. These spontaneous activations create small spots on the image that we call digital noise. There are two common types of digital noise chrominance (color) noise and luminance (monochromatic) noise. Chrominance noise results in random speckles of color seen in black or dark areas of the image. Luminance noise results in random speckles of gray throughout the image. The higher the set ISO, the more digital noise is introduced into the image. Fortunately, all digital cameras have noise suppression programs built into the software. Furthermore, when images are shot in a JPEG mode, additional noise reduction is applied in the JPEG conversion. RAW images do not have this second noise suppression algorithm applied and typically have much more noise than JPEG images. Post-production editing software has very sophisticated noise reduction algorithms than can reduce both the color and luminance noise at the cost of losing some image sharpness. Part of the post-production workflow for RAW images is to sharpen and apply noise reduction. There must be a balance between these two processes because sharpening causes noise to be more prominent and noise reduction causes a lack of sharpness.
Two factors that can ruin a great photo even more than improper exposure are lack of focus or blurring of the subject. Most of today's dSLR cameras have great auto-focusing systems that are reliable in good lighting conditions. In low light conditions or when the subject is partially obscured by bushes or trees, manual focusing can be needed. Even with proper focus on the subject there can be blur or loss of sharpness if the subject or the camera moves during the exposure. It is important to keep your shutter speed high when photographing wildlife. A good rule of thumb is the shutter speed should be faster than 1 / effective focal length of the lens. The effective focal length is the actual focal length times the crop factor of the camera. This helps to prevent camera shake that will blur or soften your image. Image stabilization in the lens or camera may allow slower shutter speeds when shooting hand-held images.
Even with high shutter speeds and image stabilization longer focal length lenses usually need mechanical stabilization in the form of a tripod or other support mechanism. A sturdy tripod is usually the best way to get sharp images. Other tools that can reduce camera shake are to use a cable or electronic shutter release mechanism to avoid contact with the camera during the exposure. With super-telephoto lenses (greater than 400mm actual focal length) it is often helpful to use the mirror lock-up function of your dSLR to reduce the vibration of the mirror movement during exposure. This can be done by switching to the 'live view' mode on the camera LCD display or a dedicated two step mirror lock-up followed by the actual shutter release.
Finally, we move to the most difficult part of good wildlife photography, composition. Good composition takes time and experience to learn. Two 'rules' often applied to wildlife photography are 1) fill the frame with the subject and, 2) the rule of thirds - placing the subject at the intersection of horizontal and vertical lines dividing the image into thirds. Another 'high value' rule to to have the subject looking into the frame rather than to the outer edge of the image. Framing the primary subject with grass, bushes, rocks, trees or the landscape often creates a pleasing image. Lastly, patterns and leading lines help to focus the viewer's attention on the subject. I will post more thoughts about composition in wildlife and nature photography in another post.
Wildlife photography requires the perfect mix of subject, location, lighting, gear, technique, and composition. It also requires that the photographer be ready to shoot on a moment's notice and, more often than not, a little luck. Good shooting.