What is ISO?
ISO measures the sensitivity of the camera sensor to light.
The term ISO is from the days of film. Film is made up of little crystal grains. At ISO 100 or 200, those crystal grains are very tiny and need more light to expose them. With ISO 1600 or 3200 film, the crystal grains are larger and thus need less light to expose them. The trade off is that the larger crystal grains are more noticeable and photos are less smooth.
Digital cameras have ISO equivalents. However, with digital cameras it isn’t crystal grains that become noticeable as the ISO numbers get larger, it is pixels.
At higher ISOs, your camera sensor will need less light to create a nicely exposed photo. However, you will also see more grain/noise in the photo. At lower ISOs, your camera sensor will need more light to create a nicely exposed photo and you will see much less grain/noise in the photo.
(Taken at ISO 6400 on a Nikon D610. At 100% grain is noticeable but not distracting. No noise reduction has been applied.)
What ISO Should I Use?
As a general rule, you want to keep your ISO as low as possible. However, this doesn’t mean that I will always photograph at an ISO of 100. When photographing indoors there is much less available light than there is when I am photographing in the sun. In those situations, I use whatever light I have available and raise my ISO as necessary to get a good exposure. Why? Because capturing a nicely exposed photo is more important than worrying about grain or noise.
- Use lower ISO numbers when you have lots of light available (i.e. outdoors where there is nice light.)
- Use high ISO numbers when you have little light available (i.e. indoors in the evening, or outdoors as the sun is setting)
Digital cameras have really improved their high ISO capabilities in the last several years. Many current cameras have the ability to shoot at high ISOs with relatively little grain/noise.
Changing ISO on Your Camera
To adjust ISO on your Canon Camera, press the ISO button and rotate the main command dial. The ISO button is found on the top of the camera in one of the locations on the diagram below.
To adjust ISO on your Nikon entry-level camera, press the "Info" button and using the back circular dial select ISO and then set the number you want and press "OK". Some entry-level Nikon camera's have touch screens that allow you to adjust ISO using the touch screen. TIP: Since setting ISO requires a few steps, consider setting the "Fn" button on the front of your camera to adjust your ISO. Consult your manual for the exact steps to do this.
To adjust ISO on your Nikon pro or semi-pro camera, press the ISO button and rotate the main command dial. The ISO button will either be located on the top or back of your camera depending on the model.
Lower ISO numbers are less sensitive to light and produce little noise or grain. Use them when you have lots of light. Higher ISO numbers are more sensitive to light but produce more grain or noise. Use them when you have little light available to you.
Don't Miss the Next Posts in This Series!
I hope this series has helped you Master Shooting in Manual Mode. If you’ve missed any of the posts in the series, you can go back and read/review them at any time by following these links!