By the definition of ISO is a measure of the level of the camera sensor sensitivity to light. The higher the ISO setting, the more sensitive we terhada light sensor.
To get a clear picture of our ISO setting on the camera (in the case of film photography ASA), think about a bee community.
1. An ISO is a worker bee. If my camera set at ISO 100, it means I have 100 worker bees.
2. And if my camera set at ISO 200 means I have 200 worker bees.
Is the duty of every worker bees collect light coming through the lens of a camera and make a picture. If we use the identical lens and aperture together we set at f/3.5 but I set the ISO at 200 while your 100 (think again about the worker bees), the images have who will finish faster?
1. When we increase the ISO setting from 100 to 200 (the aperture is always a constant – we lock the aperture at f/3.5 or through Aperture Priority mode – A or Av), we shorten the time needed in making a picture in our camera sensor by half (2 times faster), shutter speed of 1/125 to 1/250 sec.
2. When we add more ISO to 400, we cut back to half again making photographs: 1/500 sec.
3. Whenever esksposur shorten as much as half, we call esksposur increase by 1 stop.
You can try this sense in the case of aperture, shutter speed set we try always constant at 1/125 (or via the Shutter Priority mode – S or Tv), and change-change your ISO setting in multiples of 2, for example from 100 to 200 to 400 etc, look at the amount of change your aperture.