ISO* settings on a camera affect how sensitive the film — or image sensor in digital photography — is to light. The higher the ISO, the more sensitive it is and the brighter your photos will be.
In low light situations, it is often necessary to raise the ISO in order to get a clear picture. The big problem with raising the ISO, though, is that it introduces ‘noise‘ into the image (we talk about this more below), which can make it appear grainy.
If you are taking a picture in ideal light conditions, you will want to keep the ISO low in order to avoid introducing noise into the image.
Generally speaking, though, you’ll want to experiment with different ISO settings to see what gives you the best results in different lighting conditions.
* In case you’re curious, ISO stands for International Organization for Standardization.
How is ISO measured?
ISO is measured in numbers, with lower numbers being less sensitive and higher numbers being more sensitive. The most common ISO values are 100, 200, 400, 800, 1600, and 3000.
The lowest ISO setting or base ISO is typically 100, although some cameras go as low as 50 or even 25. Some older cameras will start at ISO 200.
Remember: the higher the ISO number, the more light you are letting into your photo.
Which ISO setting should I use?
It’s hard to give general advice, especially as camera technology improves. Not too long ago, an ISO over 800 would produce some noise in your picture unless the conditions were perfect (see below for more about noise).
With better cameras, though, the risks of selecting the wrong ISO are lower.
That said, here’s a general guideline.
- ISO 100: Use this for sunny, outdoor settings. Don’t rely on this setting if there isn’t enough light. If you’re in my part of the world, this setting won’t be used nearly as often as you’d like 💨
- ISO 400: In this range, we’re talking cloudy days with imperfect light. You could also use this for indoor settings if the light is very good. You’ll have less light entering the camera, but also less noise.
- ISO 800: Use this for indoor settings with less amount of light. Once you’ve hit 800, you’re starting to risk noise entering your picture, so proceed with caution!
- ISO 1600, ISO 3200, ISO 6400+: This is for pictures in the dusk and evening, where light is imperfect.
How to change ISO settings on your camera
To change the camera ISO on most DSLR and mirrorless cameras, you will need to go into your camera settings and find the ISO setting. Other cameras might have a specific ISO button.
Once you have found it, you can use the + and – buttons to adjust the ISO up or down. When you are finished, be sure to press the menu button to save your changes. With a little practice, changing the ISO on your camera will become second nature.
If you’re not sure, many modern cameras will let you choose ‘auto ISO’. You can select the maximum range, and then set shutter speed and aperture. The camera will take care of the rest!
Understanding ISO and ‘noise’
In photography, noise refers to the random variation of brightness or colour values within an image. It can be caused by a variety of factors, such as heat, electrical interference, or camera sensor defects. Noisy images often appear grainy or blurry, and can be difficult to print or enlarge without losing quality.
Although noise is generally considered to be undesirable, some photographers intentionally introduce it into their images for artistic effect.
When used sparingly, noise can add texture and depth, giving an image an organic, vintage feel. In recent years, digital noise reduction techniques have made it possible to significantly reduce noise levels in digital photographs. However, even with these advances, noise remains a common issue that all photographers must contend with.