ISO

“Conventional film comes in different sensitivities (ASAs) for different purposes. The lower the sensitivity, the finer the grain, but more light is needed. This is excellent for outdoor photography, but for low-light conditions or action photography (where fast shutter speeds are needed), more sensitive or "fast" film is used which is more "grainy".
Likewise, digital cameras have an ISO rating indicating their level of sensitivity to light. ISO 100 is the "normal" setting for most cameras, although some go as low as ISO 50. The sensitivities can be increased to 200, 400, 800, or even 3,200 on high-end digital SLRs. When increasing the sensitivity, the output of the sensor is amplified, so less light is needed. Unfortunately that also amplifies the undesired noise. Incidentally, this creates more grainy pictures, just like in conventional photography, but because of different reasons. It is similar to turning up the volume of a radio with poor reception. Doing so will not only amplify the (desired) music but also the (undesired) hiss and crackle or "noise". Improvements in sensor technology are steadily reducing the noise levels at higher ISOs, especially on higher-end cameras. And unlike conventional film cameras which require a change of film roll or the use of multiple bodies, digital cameras allow you to instantly and conveniently change the sensitivity depending on the circumstances”
This week, I will be covering on what ISO is. Many people might not be aware of what is it, but ISO is actually a form of a speed to help boost a DSLR’s shutter speed. The advantages of it are that if you were in a dark environment and need a faster shutter speed to shoot, ISO comes in very handy. And especially now with better technology, ISO speeds can go to as high as ISO 12 800 compared to ISO 1600 almost eight years ago.
However, ISO has its disadvantages as well. If too high a ISO speed is used for an image. The image quality will turn out very bad, the pixel-like dots you see on the.”