Exposure Basics: How to Choose ISO, Aperture, and Shutter Speed Settings

If you’re trying to break free from the auto settings on your camera and make an entry into the world of manual, it’s necessary to understand ISO, aperture, and shutter speed–in addition to knowing how to make them work for you. In this quick video clip, John Greengo does an excellent job of explaining how to get all three of the settings working together to make properly exposed photos:

To find the optimal exposure value, it’s a good idea to start by thinking of aperture, shutter speed, and ISO separately.


Envision the photo you want to take and decide which aperture setting would create the result you’re after. For example, if you want everything in sharp focus, choose a small aperture (bigger number). If you prefer to blur the background, opt for a wider aperture opening (smaller number).

Shutter Speed

Shutter speed determines whether you freeze or blur action. Decide how you want action portrayed in your photo, and go for a fast shutter speed if you’d like to capture your subject frozen in the air.


Most of the time, you’ll probably want to start with a low ISO to prevent noise.


Your ideal exposure settings might not match what’s actually possible.

Prioritize Your Choices

Now that you’ve chosen your ideal settings, you’ll likely see that your camera’s exposure meter is way off. Decide which of the three exposure components is most important to you, and adjust your settings until you get a good exposure reading. For example, you might raise your ISO or sacrifice the sharpness of the background in order to freeze action.

manual camera settings

Manual Camera Settings for Capturing Fast Action

In the video, Greengo shows an example photo of an eagle grabbing a fish from a stream and discusses which settings he uses. Though he wanted to shoot at an ISO of 100 to achieve the best possible image quality, he ultimately decided to boost the ISO all the way up to 800 to gain correct exposure. He decided on boosting the ISO because his aperture was already at its widest opening to let in the most light and he couldn’t slow down the shutter speed and still be able to freeze the fast action.


Greengo’s choice in aperture, shutter speed, and ISO resulted in this image that froze the eagle’s action and blurred the background.

“…this is something you can predict and dial in ahead of time. This is something that, once you get good at this, your brain will process it in about three seconds, but it’s nice to slow this process down and take it one step at a time.”

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One response to “Exposure Basics: How to Choose ISO, Aperture, and Shutter Speed Settings”

  1. John M says:

    There is a common misconception that “Exposure” is a factor of shutter-speed, aperture and ISO – but, actually, ISO is not a component in the determination of exposure.

    Instead, ISO describes the level of amplification of the signal taken from the sensor AFTER exposure has occured … typically, to “brighten” the captured image.

    See here for the formal definition; https://en.wikipedia.org/wiki/Exposure_(photography)

    This fact has an important practical implication for capture of the “best” exposure from your camera’s digital sensor – as explained here; https://www.dpreview.com/articles/8148042898/exposure-vs-brightening

    Regards, John M

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