(Last Updated On: June 16, 2019)

Understanding ISO

ISO refers to how sensitive the camera’s sensor is to light. The higher the ISO sensitivity number, the less light is required to make an exposure. Use ISO, coupled with aperture and shutter speed, to achieve the “correct” exposure.

Auto ISO: When this menu function is chosen, the camera will automatically, almost magically, select the necessary ISO if optimal exposure can not be achieved at the ISO value you’ve dialed in. Turn this feature ON, then just shoot away. You won’t have to worry about lighting or shutter speeds – just concentrate on composition.


  1. I have a 70-300mm lens. For some reason, my pictures aren’t as clear and crisp as I would like. I love photographing trees, and lakes; the tree leaves look blended together, and the sunlight is too light, or too dark. I was told by a friend who is a photographer that I probably should set my ISO to 400, and get a monopod, to make my photos more stable…. My friend is very busy, so I don’t want to bother him, but I don’t know how to set the ISO to 400. I have a Nikon, and bought a Sigma telephoto lens, which seems to work well at times, but at other times, I’m not satisfied at all…I know it’s my fault, LOL, but I don’t know how to correct it! Also, he said to set the shutter speed faster (or higher), and I need to know how to do that as well. 🙂 Thanks!

  2. Valerie, I think the information you are looking for is on the page that explains what ISO is. Once you know what effects it has on your pictures it’s pretty easy to choose the best ISO for the shot you’re taking (typically the lowest you can get away with).

  3. Would have liked to see some information about NOT using Auto ISO. I.e. what types of settings to use in certain scenarios. I don’t like to use my camera on auto mode, & I’m interested in learning more about what options I have in manual mode. Thanks.


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