ISO

ISO 100

ISO 100

Let's begin with the first, most fundamental property: ISO

ISO refers to the sensitivity  to light for either our roll of film or the digital sensor built inside a camera.

The lower the ISO number (25-200), the less sensitive it is to lightA low ISO is often the preferred choice for bright daylight conditions. 

With an ISO of 800 or more, sensitivity increases and we can shoot in low-light conditions. If we're outside in bright conditions, this increased sensitivity means we can shoot with a very fast Shutter-Speed, so we can freeze things in motion.

A camera's "Sports" setting sets a high ISO value for us.

A side effect to ISO is the grain (film) or noise (digital) found in an image. Low ISO values have a tight grain/noise structure, making it virtually unnoticeable, but as we increase to a higher ISO, this structure starts loosening up, dramatically increasing its visibility.

A low ISO value has a tight grain/noise structure, making it virtually unnoticeable, but as we increase to a higher ISO, this structure starts loosening up, dramatically increasing its visibility.

Sometimes this is exactly  what we want, other times it's not.

Analog film's grain is more pleasing to the eye, while digital's noise is the worst.

The photographs used in this example cover ISO 100 to 12,800. The images were magnified to 400%, then cropped to really  show the effect of grain/noise.

Notice how the grain/noise is not really visible at ISO 100, 200 and even 400, but at ISO 800, it then starts to become visible. As we increase sensitivity, it becomes even more pronounced and horrendous.

So when I am trying to determine my exposure, the ISO is the first property I set.

Powered by SmugMug Owner Log In