What’s important to the photographer is the sensor size and the camera software used to process the image. The rule of thumb is the larger the sensor size, the better the camera will perform at high ISO and long shutter speeds. For a set amount of photosites, larger sensors will have a better signal-to-noise ratio, resulting in less noise.
Another aspect that affects ISO performance is the camera software. Camera companies are continually improving their image-processing software to produce cleaner digital images with less noise. With sensor size being constant, if I compare an image shot from one of my early digital cameras to one I recently bought, the new camera produces dramatically less noise. The good news for photographers is that sensors and software continue to improve with each new camera release, so expect even less noise in the future. If you really want to see how your camera’s sensor stacks up, take a look at DxO Labs’ analysis of raw image quality (www.dxomark.com).
The ISO AdvantageI remember talking to Dave Black (www.daveblackphotography.com) when the Nikon D3 first came out. This was Nikon’s first large-sensor (FX-format) camera. He told me this camera would change the way I photographed and open up new possibilities in low-light photography. Dave is an incredible photographer, and this was a huge statement coming from him. ”Change the way I photographed...” He was right.
When I started out in photography, aperture and shutter speed were used to control your exposure. ISO was a constant, except on rare occasions when you pushed film one or two stops. Photographers just didn’t think about changing ISO because the side effect of increased grain quickly degraded image quality.
But with today’s cameras, I’ve had to adopt new shooting habits. ISO is equally as important as shutter speed and aperture in controlling the light. Some cameras offer an “auto ISO” function that allows you to maintain a constant aperture or shutter speed shooting in variable light. The camera simply changes the ISO to maintain your shutter speed or aperture. ISO performance is so good that it’s no longer taboo to change it. So dial up your ISO and try one of the following techniques to experience the ISO Advantage.
1. Freeze The Action. One of the obvious ways to use high ISO is to freeze the action, even in very low light. While photographing bears in Katmai, I really wanted to freeze their “salmon-strafing runs.” The bears would plow down the middle of a stream chasing salmon, splashing water and literally chasing fish up onto the rocky beach. To capture this scene, especially freezing the water droplets, I needed a fast shutter speed, 1?1000 sec. or faster. Even though we had decent light, I still dialed my ISO up to 800 to get fast shutter speeds.