ISO

On most digital cameras there is a button or menu setting that enables you to choose the ISO setting. ISO, which stands for International Organization for Standardization, refers to the light sensitivity of your camera. ISO ratings originally applied to film speeds, such as 200, 400, and so on. Just like film, the higher the number rating, the more sensitive the sensor on your digital camera is to light. For example, if you need your camera to be very sensitive to light, such as when you are shooting in low light, then you’d want to choose an ISO of 800 or higher. The ISO setting is often the easiest variable to manipulate when you need a specific aperture and shutter speed combination.

Generally speaking, in order to keep your photographs crisp and free of noise, you should use the lowest ISO you can while still keeping your preferred shutter speed and aperture. On most cameras, ISO 100 is the lowest setting. When you use higher ISO settings — generally 800 and higher — you begin to see noise in your images, which gives a grainy appearance.