 Photography is all about capturing light. A camera captures the light that enters through the lens, using a sensor to digitise the information and create a photograph. Digital SLR cameras have a whole range of features, lenses and accessories to change and optimise the light that goes into the camera. This video looks at ISO, which refers to the sensitivity of the digital sensor. The vast array of dials and settings you get on a good camera can be quite daunting at first. In fact, most people start on the green square setting that gives almost full automatic function to the camera. However, to get the best out of a camera and be truly creative, it's best to take some time and understand how to use some of the manual functions. This will greatly affect the outcome of a photo to suit whatever your creative needs. To switch your camera to manual mode, simply turn the dial to M. ISO is essentially the sensitivity of the sensor that captures and records light going into the camera. You can adjust the sensor sensitivity to capture more or less light depending on how much is available to you. For low light or dark situations, you want the ISO to make the sensor much more sensitive. This will allow it to capture as much light as possible to compensate for the lack of light available. So let's take a look at the ISO sensitivity scale to understand what level we might need. A low ISO between 100 and 400 is best used when the surrounding light is bright. A mid ISO between 800 and 3200 comes into play for indoors or when the weather is overcast, for example, and the light is poor. A high ISO between 6400 and 51200 is what you'll need for low light photography. This is where the sensor is at its most sensitive and will amplify the light to compensate for the lack of light. Ideally, you want to keep the ISO number as low as possible as this will give you the best image quality. When increasing your ISO, it is important to note that images can have more noise or grain than images captured at lower ISO. As you can see here, selecting higher ISO numbers increases the sensitivity of the sensor making the photo brighter. The higher the camera specification in the Canon camera range, the higher the ISO scale. For example, most entry-level digital SLRs go up to 25600 ISO. The more advanced cameras can go to 51200 ISO and higher. There are three fundamental factors that are important for every photographer to understand. All of which affect the amount of light that goes into the camera and how the camera performs. These are one, the aperture, two, the ISO number, and three, the shutter speed. They all work in tandem with each other and are therefore often referred to as the exposure triangle. We recommend you take a look at our separate videos that go into more detail about aperture and shutter speed.