ISO Concept

ISO Concept is analog with ASA setting in celluloid film photography. ISO is defined as the level of sensitivity of camera sensor to the light. ISO Concept is one of three angle photographic triangle. Higher ISO setting makes the sensor more sensitive to the light.

Parable of ISO Concept we can imagine the bees community:

1. An ISO is a worker bee. ISO 100 setting means we have 100 worker bees. ISO 200 setting means we have 200 worker bees, and so on. 
2. Each worker bee will get the light entering to the camera to make the image. If you and me use the same camera and we set the aperture to f/3.5. I set the ISO to 200 but you set the ISO to 100. Whose image completely finished faster?

Outline of ISO Concept:

1. Upgrading ISO setting from 100 to 200 in the same aperture (we can set aperture to f/3.5 or lock the aperture with Aperture Priority Mode – A or Av) will reduce the time to make image to the camera sensor two times faster. The Shutter Speed will change from 1/125 second in ISO 100 to 1/250 second in ISO 200.
2. If we set ISO to 400, it will make the Shutter Speed become 1/500 second, and so on.
3. Reducing exposure time into half value is called exposure 1 stop up.

In case of aperture you can set the shutter speed constantly at 1/125 second for instance, by setting the Shutter Priority mode – S or Tv), and try to change the ISO setting from 100, 200, 400, and so on. Look at the aperture of each ISO setting.