Tuesday, September 1, 2009

ISO and Digital Noise

If you read this post about ISO, you should have a basic understanding of what ISO can do for you when you are photographing.  And while a basic understanding is good, it is still basic.  When it comes to using the ISO setting on your camera, it is important to understand not only the advantages of being able to control ISO, but also the disadvantages of doing so.

As I said in my original ISO post, increasing your ISO allows you to take pictures in darker settings without having to adjust your shutter speed or aperture.  The problem with increasing your ISO is that your camera will produce more "digital noise."  Your camera will do its best work at its minimum ISO and as you increase the ISO, you will increase the digital noise.  What does this mean?  Take a look at the pictures below.

I took a picture of this scene at every ISO setting on the Nikon D40 and then zoomed in so you can see how the ISO affects digital noise.

Try to ignore the blurriness (especially at ISO 400) which I will explain tomorrow.  Notice the increasing discolored grainy dots as the ISO goes up - that's digital noise and it can ruin a picture.  This is why you need to be careful as you increase your ISO in darker situations.  Note that ISO 3200 is called "HI" on the D40, probably to deter you from using it.