The quality of images taken at high ISOs on current cameras means you can now shoot even when the light levels are low…
ISO is simply a measure of how sensitive your camera’s sensor is to light – at high ISO settings, such as 800 or 1600, the sensor needs less light to provide a correct exposure. If you don’t increase the ISO in low light, a shutter speed fast enough to shoot handheld might not let in enough light for a correct exposure – increasing the ISO makes the sensor more sensitive, so the limited amount of light provided by the fast shutter speed (in other words, a short exposure) should be enough for a correct exposure. a faster shutter speed – perfect for avoiding both camera shake and blur due to subject movement. However, despite these advances, there is still some drop-off in quality as you increase the ISO, so you should try to keep the ISO at the lowest setting that will still allow you to get the shot. When you’re shooting in low light but want to use a fast shutter speed, set your SLR to shutter-priority mode to allow you to choose the shutter speed you need to freeze any movement. Now point your camera towards your subject and check whether the aperture display is constantly lit or flashing. If it’s constantly lit there’s enough light to start shooting, but if it’s flashing then you need to increase the ISO until it’s constant. Flashing indicates that the camera cannot achieve a correct exposure for the lighting conditions, but remember that if the light changes or the subject moves into a darker location, you’ll need to watch out for the flashing aperture display again, and change the ISO to compensate. Most Nikon SLRs offer a range of ISO settings above the ‘native’ highest values. These are known as ‘expanded ISO settings’. These are best avoided in all but the most extreme shooting conditions, as along with increased noise, which shows up in the form of speckles on your photographs, using these settings can also lead to a greater risk of blown highlights and blocked-out shadows, as they often have a lower dynamic range than the normal ISO settings.
White balance is essentially a way of ensuring that whites actually look white in your images