June 23, 2014

Q&A: What is ISO and How Should I Set It?

A look at what ISO is and how it should be set.

Welcome to the first week of the Exposure Q & A series!

We had a lot of awesome questions submitted but the one from Tara about ISO really stood out so we’re taking this opportunity to explain some of the basics about this important setting…

What is ISO?

Before getting into what ISO is let’s talk about how it relates to the overall exposure of an image.

ISO is one of the 3 main elements in something call the “Exposure Triangle”. The exposure triangle is a term used to explain the relationship between ISO, Shutter Speed, and Aperture. To correctly expose an image (ensure it’s not too dark or too bright) all three settings must work together. If any one of those three settings changes, the others must change to maintain correct exposure. Typically in any camera mode other than Auto you will have to manually set ISO.

So how do you know what to set it to?

On it’s own ISO simply represents how sensitive the camera sensor is to light. The lower the number (say, 100) the less sensitive and the less light that will be “absorbed” by the sensor. The higher the number (say, 3200) the more sensitive and the more light that will be “absorbed” by the sensor. As the ISO is increased the amount of “noise” (that grain or snow you can see in low light images) also increases. Thus, whenever possible it’s best to keep the ISO setting as low as you can while still maintaining a correct exposure. So, if you are shooting in a mode that requires you to adjust the ISO it’s usually best to start with the lowest possible ISO setting (100 or lower depending on your camera) and only increase it as necessary to keep the scene exposed correctly.

This is really just the tip of the iceberg when it comes to ISO and the exposure triangle. There is so much more to learn and we’d love to teach it to you. Keep an eye on our class list for courses ranging from camera basics to the more creative and artistic.

Happy Shooting!

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