Introduction to ISO in Photography

What is ISO?

In very basic terms, ISO is simply a camera setting that will brighten or darken a photo. As you increase your ISO number, your photos will grow progressively brighter. For that reason, ISO is a good tool to help you capture images in dark environments or be more flexible about your aperture and shutter speed settings.

However, raising your ISO has consequences. A photo taken at too high of an ISO will show a lot of grain, also known as noise. You should only raise your ISO when you are unable to brighten the photo via shutter speed or aperture (for example, if using a longer shutter speed would cause your subject to be blurry).

Every camera has a different range of ISO values (sometimes called ISO speeds) that you can use.

ie – ISO 100 (low ISO), 200, 400, 800, 1600, 3200, 6400 (high ISO) Quite simply, when you double your ISO speed, you are doubling the brightness of the photo. So, a photo at ISO 400 will be twice brighter than ISO 200, which will be twice brighter than ISO 100

What ISO Should You Use?



Many photographers understand the basics of ISO, but they aren’t sure which ISO value to actually pick in the field. In practice, there’s a reason why your camera allows such a wide range of ISO settings: Different situations call for different ISOs.

When to Use Low ISO

As discussed above, you should always try to stick to the lowest ISO of your camera, which is typically ISO 100 or 200, whenever you can. If there is plenty of light, you are free to use a low ISO and minimize the appearance of noise as much as possible.

When to Use High ISO

Even though it is ideal to use low ISOs, there will be plenty of times when a high ISO is necessary in order to take a good photo in the first place. For example, you may want to use a higher ISO for dim lit situations or even to stop action.

To maximize your image quality, here are the four steps you need to follow:

  1. Select the aperture setting that will provide your desired depth of field.
  2. Set your ISO to its base value, and put your shutter speed to whatever setting provides a proper exposure.
  3. If your subject is blurry, progressively raise your ISO and use a faster shutter speed until motion blur disappears.
  4. If your ISO is getting too high and you still have the ability to use a wider aperture, open it up until the ISO gets to a more manageable level, even if it means sacrificing some of your desired depth of field.

That’s all it takes! If you follow these steps, you’ll capture the maximum image quality each time. You’ll find the ideal balance between noise, motion blur, and depth of field.