ISO (what used to be known as ASA) refers to the “light sensitivity” of the digital chip or sensor. Lower ISO numbers (100) require a lot of light to record a picture, while higher numbers (400 – 800) can record in relatively low light. If your camera gives you a choice of ISO settings, they will most likely include: Auto (the camera makes the selection), 100, 200 and 400. In most cases, it’s best to rely on the Auto setting to choose your ISO. Also, beware of 400 or higher, because the result is often grainy pictures.