ISO – The Simple Explanation!
In Digital Photography, the ISO is the setting that adjusts how sensitive your camera's sensor is to light. It usually ranges from 100-64,000+ on most cameras. The higher the number, the less sensitive it is to light. This means that if your ISO was set to 64,000, you could expose a candle-lit dinner accurately. However, if you were outside on a sunny day, your ISO must only be set to about 100. So, the ISO is what the camera uses to measure how much light hits the sensor.