This week we are talking about the final component of the exposure triangle: ISO! This is the third post in a series about how to shoot with your camera on manual mode. In week one we covered aperture, followed by shutter speed in week two. If you missed them, be sure to go back and check them out!
In digital photography, ISO is a measurement of how sensitive your camera’s image sensor is to light. If you shoot with film, ISO will refer to the light sensitivity of the film itself. ISO stands for “International Standards Organization” and is just a standard scale for measuring the sensitivity.
The greater the ISO value, the greater the camera (or film’s) sensitivity to light. The more sensitivity, the brighter your image will be. In film photography, the ISO is determined by the film and can not be changed. However, in digital photography, you can control the ISO yourself. Increasing your ISO will increase the brightness of the image, while decreasing the ISO will make the image darker.
ISO has a direct impact on the amount of digital noise (or grain if you shoot on film) in your image. The higher the ISO, the more noise you will encounter. Noise is most common when shooting in low-light situations when the ISO is raised in order to brighten the image. Noise doesn’t always have to be a bad thing, though! Some photographers use noise to mimic the grain found in film photos as an artistic effect.
In the images below, you can see how increasing ISO increases the digital noise. The left image was shot at ISO 3200 and in the close-up you can see the graininess. The right image was shot at ISO 250 and the close-up appears much smoother.
Most DSLR cameras will allow you to manually set your ISO if you are in Manual, Aperture Priority, Shutter Priority modes. Pick one of the fore-mentioned modes and determine the subject of your photograph. Experiment by increasing and decreasing the ISO to see how your exposure changes.