There is a fantastic setting on your camera labeled “ISO”. It is kind of a mysterious but super helpful setting, if you know how to use it properly. When changing the ISO setting on your camera, you are changing the sensitivity of the camera’s sensor to light. Understanding the concept of ISO settings and when to change them will help you to improve your photography in a dramatic way.
Would you like to learn a truly trivial fact? ISO stands for International Standards Organization. It comes from the days of film and was a rating system for film speeds. But now that mystery has been solved, so let’s move on to what ISO is and how it affects your exposure.
ISO simply controls the amount of light being let into your camera. You will typically see numbers like 100, 200, 400, 800, 1600, etc… when looking at your ISO settings. Higher end DSLRs will have settings ½ or 1/3 of the way in between those settings. A smaller ISO setting lets in less light while a higher ISO setting lets in more light.
ISO settings of 100, 200 or even 400 are typically settings used for photographing outdoors. A bright, sunny day would probably best be shot at ISO 100 while on an overcast day an ISO of 400 may be more appropriate. ISO settings of 800 and higher are appropriate to use indoors or at night where you will have less ambient light to work with. You may also need a higher ISO when you have plenty of light but need a faster shutter speed or smaller aperture…but we will talk about those in the weeks to come.
Bumping up your ISO to a higher setting makes it possible to capture great exposures in situations that seem to have to little light. There is a drawback to using a higher ISO, however. The higher the ISO, the more “grain” or “noise” will be visible in your image. Noise tends to be more prominent in the shadows of an image and can become excessive if your image is underexposed. It is better to capture a properly exposed image with some noise than to capture an underexposed or blurry image with less noise.
One thing to keep in mind is that the quality of noise in your images will vary depending on your camera. Entry level DSLRs tend to display much more noticeable noise and lower quality images at higher ISOs while higher end DSLRs will display noise, but the image quality is still high. The images you see below are examples of well exposed images at various ISO settings. These were all shot with my Canon 6D which is a great camera that does a wonderful job of capturing quality images in low light (with the proper exposure settings set by the photographer, of course).
I hope this helps to demystify the concept of ISO settings!