What does ISO means in terms of photography ?
ISO (or ASA) denotes is how sensitive the image sensor is to the amount of light present. It is measured in numbers (you’ve probably seen them on films – 100, 200, 400, 800 etc). The lower the number the lower the sensitivity of the film. For example, in solid daylight you should often never need to go over an ISO of 100. Whereas at night, when there is little light, you might have to set it to around 800.The only disadvantage of having the ISO higher is that the images are subjected to much more noise. Most people tend to keep their digital cameras in ‘Auto Mode’ where the camera selects the appropriate ISO setting depending upon the conditions you’re shooting in (it will try to keep it as low as possible) but most cameras also give you the opportunity to select your own ISO also.