ISO SETTINGS IN DIFFERENT SITUATIONS
Always use the lowest possible ISO value.
I’m in the last wave of photographers who learned to photograph with film cameras, and I can fully appreciate the fact that I can change my camera’s sensitivity to light, on the run, with one button. I’ve been photographing for about 13 years—almost half of it with a film camera. Slow film speed was the biggest challenge in bird photography. Nobody in their right mind used film speed over ISO 400. If you wanted beautifully reproduced colors with no grain, you had to use Fuji Velvia, a very slow film with an ISO of 50. Digital cameras today produce the same image quality at ISO 1000 as Velvia does at ISO 50, which is the biggest single reason behind the revolution that took place in bird photography in the few years during the change from film to digital.
How should you use your digital camera? What are its technical limits, and what ISO values should you use in different situations? Never mind the leaps taken in technology—you can’t bend the laws of physics. The rule still applies that the lower the ISO value, the better the quality of your image. So when you do not need a fast shutter speed, stop down one or two f-stops and lower the ISO as much as possible to result in less noise, better colors, and better overall picture quality. Low ISO values will also give you more range for sharpening the image with little to no loss of quality.
One option is to use auto ISO, which automatically alters the ISO setting to get the right exposure for the given aperture and shutter speed combination, but I don’t use it. In bird photography, I prefer to adjust the aperture, shutter speed, and ISO myself to suit each situation.
I set the shutter speed based on my subject, normally either to 1/2 second to 1/100 second, or faster than 1/1000 second. Other values are either too fast for motion blur or too slow to freeze movement.
When I want to emphasize motion in an image, I go for a low ISO to guarantee the best possible image quality. Then I set the shutter speed as described earlier, and then I adjust the aperture according to the exposure meter. Don’t worry if your background is busy or ugly because the movement will blend the elements together as the camera tracks the subject. Watch out for diffraction, though, because it will weaken the image quality when the aperture is smaller than f/11.0—I don’t use a smaller aperture unless I absolutely have to.
When you want to use the fastest shutter speed possible, use the largest aperture and raise the ISO as high as you can without getting too much noise in the image. If I can get shutter speeds of 1/1000 second to 1/2000 second, I will use these settings, but if they produce a faster shutter speed than I deem necessary based on experience, I lower the ISO or stop down 0.5 to 2.0 f-stops, which helps improve the image quality.
The highest possible ISO varies from one camera to another; it is also one of the fastest developing areas in digital camera technology. As of this writing, photographing birds with ISO 12800 produced good-quality images; for example, see the Golden Eagles in the chapter “Bird Photographer’s Camera.”
Burrowing Owls in the low light of twilight just after sunset (Athene cunicularia)
Nikon D700, 300mm f/2.8, 1/320 second, f/2.8, ISO 1600, manual focus, Gitzo tripod and video head, blind. Pantanal, Brazil, November 2009.
These settings aren’t absolute, they are just settings that I use most often in the field. In bird photography, sometimes even 1/4000 second is not enough to freeze movement, so I improvise all the time, adjusting to the situation and the circumstances. A photographer has to evaluate each situation and decide how to prioritize shutter speed, image quality, and depth of field to get the best results.
A shutter speed of 1/13 second was just slow enough to create motion blur with the movement of the Red-and-green Macaws and the background (Ara chloropterus)
Nikon D700, Sigma 300–800mm f/5.6, 1/13 second, 650mm, f/16.0, ISO 100, continuous focus, Gitzo tripod and video head. Buraco das Araras, Brazil, February 2010.