Secrets of ISO, Exposure and Noise

The purpose of this article is to clear up myths and misinformation about image exposure, ISO, and noise. So, what is exposure exactly? Exposure is simply the amount of light reaching your sensor or film in a given amount of time. The amount of light reaching your sensor is determined by the length of time the camera’s shutter is open, and the size of the opening in your selected lens model.

An underexposed image is one that has not received enough light to create a good image, while an overexposed image is one that has received too much light while the shutter is open. You might hear some photographers speak of a concept called the “exposure triangle”. The exposure triangle is a fundamental photography concept balancing three key elements, aperture, shutter speed, and ISO, to determine an image’s brightness and creative style.

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Steven W. Krull is a renowned photographer and author who has been photographing and writing of the beauty and wildlife of the Colorado Rocky Mountains for over two decades. Please visit his website at S.W. Krull Imaging to view his work, including thousands of prints for sale, stock images for commercial use, and his library of published books.