Exposure Tutorial Part Three: What is ISO?

ISO is all about measuring light.  The brighter it is where you’re taking your photos, the lower your ISO number needs to be.  Therefore if it’s dark and/ or there’s not a lot of light, then your ISO needs to be higher.  ISO numbers range from 100 to about 3200. That being said, most of the time your ISO number will be between 100-800.  The higher the ISO number the faster the camera sensor will absorb light.

So how do we know how to set our ISO? Here’s a little reference guide I made.  If you don’t attend our Fraser Valley club, here’s the image as a 4×6 printable pdf, ISO PDF

When determining how to set your ISO the main thing to think about is how much light there is where you’re taking your photo.

We also have to remember that the higher our ISO is, the  greater risk our photo is to noise.  What’s noise?  It’s that grainy speckled look that you sometimes see in photos.  In most cases, it’s considered to be undesirable.  The following two photos are examples of images with noise.  I took the photos at about 5:30pm when the sun was going down (no flash).  The kids were right next to our sliding doors, however outdoor light was very limited.  Notice that grainy look on my daughter’s skin, hair, etc?  The following photos had an ISO setting of 1600, which is way too high.  As soon as you bump your ISO past about 600 (depending on the quality of your camera and available light), you put your photo at greater risk of having that grainy look. To keep your photos sharp it’s always best to keep your ISO as low as possible.

Therefore, even though your camera may be able to reach an ISO of up to 3000, it’s best to stick around the 600 mark in order to avoid noise/ grainyness in your photos.

Shari (MWAC Host)


2 thoughts on “Exposure Tutorial Part Three: What is ISO?

  1. What iso would you recommend outside in a moderately dense forested area that does have some moderate light trickling in in lots of areas?

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