The ISO setting is used to control your camera’s sensitivity to light. When you use a high ISO setting essentially you are telling your camera to become more receptive to the available light. This is most often used when you are photographing in low light situations in order to maintain a proper exposure. However, there are at least three other reasons you might consider using a high ISO setting when you’re either in a good light situation or on a tripod.
1. Freezing fast motion
The only way to freeze fast motion, like the wings of a hummingbird moth, is to shoot with an extremely fast shutter speed. The above photograph was shot with a shutter speed of 1/8000th of a second in order to freeze the insect’s wings. However, even in the bright mid-afternoon sun, a shutter speed that fast required bumping the ISO setting on the camera to 1,000 to maintain an even exposure.
Below, is an example of why shooting at 1/8000th of a second was necessary. Even at 1/800th of a second the insect’s wings were barely visible. In order to ensure that the motion was frozen it meant that more light was needed in a shorter amount of time and the only way to get this (without a faster lens) is to bump up the ISO on the camera.
2. Night sky photography
Many different techniques come into play when you want to photographing the stars, but one of the more important things to remember is to increase that ISO setting. The reason you want to photograph the stars with a higher ISO, even though you’re using a tripod, is that as the earth rotates, the stars move across the sky and you don’t want to capture that movement in your photograph (unless you are doing star trails)
Many different techniques come into play when you want to photographing the stars, but one of the more important things to remember is to increase that ISO setting. The reason you want to photograph the stars with a higher ISO, even though you’re using a tripod, is that as the earth rotates, the stars move across the sky and you don’t want to capture that movement in your photograph (unless you are doing star trails)
By using an ISO in the 800 to 1,000 rang,e with a fast wide-angle lens, you will be able to capture enough stars to fill the sky.
3. Hand-holding a long lens
If you’re shooting handheld with a long lens, you have to remember the shutter speed rule: 1/focal length (35mm equivalent). This rule basically means that if you’re using a 300mm lens on a 1.5x crop factor DSLR then the minimum or slowest shutter speed that you can use is 1/450 (1/300 on full frame).
The bald eagle above was shot at a 450mm equivalent focal length using a shutter speed of 1/500th of second and an ISO of 1,000. Any slower on the shutter speed and you begin to run the risk of introducing camera shake.