Tennessee Photography by Bradley Proctor

Camera ISO Settings

Film has an ISO level associated with it and when it is loaded into the camera, the cameras ISO setting must be set to match. Digital cameras have an ISO setting as well, but it is usually just a setting somewhere in the cameras menu system.

What exactly do these ISO levels do?

The ISO level that you use to shoot your photos is a standard that tells how sensitive the film (or in digital photography, the sensor) is to light. The lower the ISO number, the less sensitive, and thus takes longer to expose the picture. High ISO numbers are more sensitive and allow us to use faster shutter speeds. There is a trade-off with using higher ISO levels, and that is noise.

What ISO levels should you use then?

It’s usually best to use the lowest ISO setting you can for the subject you are shooting. My camera has ISO settings from 100 to 1600. I rarely change the ISO level above 100 unless there is low light and I need the extra shutter speed, such as for a moving subject, or if I am hand holding the camera. It’s better to have a grainy picture that is in focus then a blurry picture with little grain. The set of pictures below show how noise increases the higher the ISO level is set.

The ISO level is directly related to the shutter speed. The ISO 100 picture was taken at 4 seconds, ISO 200 at 2 seconds, ISO 400 at 1 second, ISO 800 at 1/2 second, and ISO 1600 at 1/4 second. Notice also how the color seems to get a little darker at higher ISO levels. This means that Canon has overstated the ISO levels and that the ISO 1600 setting is probably closer to about ISO 1500.