FotoU: Understanding ISO

ISO is one of those lesser-known yet very important concepts that every photographer should understand.  If you understand ISO, you will be able to capture images that are impossible for a wanna-be photographer!  Which, if you’re like me, it’s not how much you know that’s important – it’s how much more you know than everyone else that matters.

Let’s first define the ISO number.  Simply speaking, the ISO on your digital camera is the speed at which the sensor reacts to light – the HIGHER the number, the MORE reactive to light.  For example, an ISO of 800 will be more reactive to light than 100.  In the following pictures, the only thing that was changed was the ISO setting.

So, you can have the same amount of existing light and get a brighter picture simply by adjusting the ISO.  This becomes very useful when you’re taking pictures in a low-light situation and you don’t want to or can’t use a flash.  For example:

So, if you’ve ever been indoors, at a basketball game, or at an assembly and couldn’t or didn’t want to use a flash – increasing the ISO is the answer.  Finally, you’ll be able to get the images that you’ve been missing!

The only drawback to increasing ISO is ‘noise.’  Noise is pixelation and discoloration of the image that is created by increasing the ISO too high and making the sensor ‘hyper-sensitive.’  Look at the following examples of images that are enlarged:

With today’s cameras, noise is not as big of an issue as it once was.  Generally, you will only see noise if you are printing an enlargement of your image.  My camera will go up to 6400 ISO!  That means I’m very cool and my high-end ISO is likely larger than yours…which is what really matters.

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