ISO

ISO is pretty easy. It is kind of like a volume knob on a stereo, but instead of sound we are talking about light. The higher you turn it up the more sensitive the camera’s sensor becomes. So, if you are outside in bright daylight, ISO 100 would be fine. Some clouds roll over and the sky darkens some you may want ISO 200 or 400. The darker it gets, the more ISO you need. That is it. Really. I said it was simple. You want more? Okay.

What do the letters ISO mean? International Organization for Standardization. Really it is ISO 5800:1987. It is a standard for film sensitivity and you can learn more in depth detail at Wikipedia. But lets not worry about that, ISO is just a number, like on that volume knob.

Okay, back to using ISO. The higher the number the more sensitive your camera’s sensor is to light. There is a small drawback to using high ISOs. The higher the ISO the more noise you will get. This is especially true with dark areas where you will get color noise along with standard noise.

Noise Examples: 100% zoom, actual pixels.

ISO 100, f8, 1.6sec

ISO 200, f8, 0.8sec

ISO 400, f8, 1/2 sec

ISO 800, f8, 1/5 sec

ISO 1600, f8, 1/10 sec

First you may notice that the ISO 100 picture was takes with a shutter speed of 1.6 seconds while the 1600 one was 8 times faster at 1/10 of a second. And okay, so there is a noise difference between ISO 100 and 1600, but it is not as big as you might think. First off, the above pictures are viewed at 100%, and that is from a 12.2 megapixel image. When I post to flickr my full size picture is only 25% and it is still 1500 pixels wide. The display size at flickr is 1/2 of that. Those little bits of noise start to disappear when they are shrunk.