In this series of quick tips and knowledge information Gaby highlights the basic stuff that every beginner photographer should know about.
If you came from the age of film, you might ba aware already of ISO used in a film camera. It is the 'speed' of the film where higher ISO value means you can take photos in lower light conditions. On digital cameras ISO value indicates your sensor's sensitivity to light where the higher the ISO, the less light is needed to take the photo that is correctly exposed (i.e. Not too dark or too light).
Setting ISO on your camera need to be aligned with the photography triple constraints: shutter speed, aperture and ISO value. This is why one setting change has an impact on the remaining two. If you (like me) choose to use manual ISO all the time then always use the lowest value i.e. 100 depending on your camera model. When composing set your ISO first to get the exposure right after with shutter speed and aperture. If in a dim situation and you don't have a tripod, set in shutter priority (TV on Canons) and choose a speed equal to or greater to your focal length (example for a lens of 180 mm set the shutter speed first at 1/200 of a second).
Consider the following settings:
100 for bright sunny day or night photography using a tripod
200 for a hazy or outdoor shade environment
400 for indoor at night or cloudy outside
800 for late night, low-light, and sporting arena at night.
Remember! Ahigher ISO is useful sometimes but it comes with a price; noise. Try avoiding higher than 1200 ISO at all time.