I would like to share a few tips on photographing some of the animals at the Omaha zoo. The Henry Doorly Zoo in Omaha Nebraska usually ranks as one of the greatest in the world. The zoo is well-laid out in basically a large circle, and is very walkable aside from a few gradual slopes. In my opinion, the first thing to do is check out Hubbard Gorilla Valley. The Valley is one of the most popular habitats and can get very crowded.
The gorillas are often right up against the glass, though they have mixed feelings about their visitors. Thus, a mid-range zoom lens is perfectly fine. A very wide aperture lens is usually not needed. The habitat is open-air and the gorillas are usually stationary or moving at a relaxed enough pace. That being said, these guys are unpredictable so be prepared for sudden movements. I usually shoot wide-open using aperture priority with continuous auto-focus and continuous high shutter. Redundant shots can be deleted, but missed shots are simply lost. Although not banned, tripods are frowned upon when they are perceived as blocking paths. Click here for the zoo's policies on non-commercial and commercial photography.
Other issues are the reflections in the glass and dealing with crowds. For reflections, placing the camera lens right on the glass so that it's perpendicular to the glass will largely eliminate reflections intruding on the image. Of course, this may not be an ideal angle for a shot so reviewing the image to minimize distracting reflections (e.g., across the gorilla's face) that can't be cropped or cloned out is critical. Similarly, watch out for scratches or smudges on the glass.
Crowds can be a big problem later during the day. For this reason, it's better to come early when there are fewer people and the light is less harsh in the habitat. Otherwise, you may have to patiently wait your turn at the glass. Another solution is to make the spectators part of the photo.
After Gorilla Valley, head over to the Orangutan Forest. Photographing in the Orangutan Forest is much more challenging compared to the Valley. The interior orangutan habitat is generally poorly lit and huge, and some of the orangutans are quite active, so a wide aperture, longer zoom lens is advisable. The hallways around the habitat also tend to be very crowded, so don't count on being able to use a tripod in this case. A monopod may be useful. Glass reflections can again be an issue. My advice is to place the camera lens right on the glass, which helps with reflections and to stabilize the lens. Having a camera with both lens and in-body stabilization is very helpful. The auto ISO feature of a camera is great in this situation because it helps provide flexibility to maintain a fast enough shutter speed to avoid camera shake. However, it's a good idea to set a maximum limit to auto ISO in order to avoid unacceptably noisy images. In addition, use continuous autofocus and bursts which will increase the odds of getting a reasonably sharp photo. Use Tony Northrup's "Rule of Doubles".
A couple more tips...Whenever you see action at Gorilla Valley or Orangutan Forest, don't hesitate to take the shot immediately. If you fiddle with your settings or try to first brace your camera against something for stability, the moment may be over. It's far better to get the shot, even if not technically perfect, than missing it altogether. Finally, focus on the eyes. This will greatly strengthen the connection between your subject and the viewer of your photo.