Photography 101: ISO


originally posted July 18, 2011

I’m still working on the 31 Days to a Better Photo, which more than likely will be a 31-week project for me. Anyway, day 4 of the series is about ISO. And what is ISO you ask? Well, evidently it’s a measurement of light sensitivity, and, coupled with the shutter speed, controls how much light is allowed into the camera’s sensor. On my camera, which is a Canon, the lowest ISO measurement starts out at 100 and goes up to 1600. Each increment doubles in size, doubling the speed at which the light enters the camera – 100 being the slowest and 1600 being the fastest.

I’ll be honest, this is about as clear as mud to me. The suggested exercise was to put the camera in Program mode (which will determine the shutter speed for you), find your subject, and change the ISO for each shot. Well I did that, starting out at an ISO setting of 100, going all the way up to 1600. All of my shots looked pretty much the same. The above shot was taken in Program mode at an ISO of 400.

So I changed my camera to Manual mode and set the shutter speed myself. Here are my results:

shutter speed: 1/125. aperture: 2.8. ISO: 100

 shutter speed: 1/125. aperture: 2.8. ISO: 200

 shutter speed: 1/125. aperture: 2.8. ISO: 400

So, what did I learn? Honestly, I’m not exactly sure. Clearly by the above example, the higher the ISO the brighter the shot. As well, the picture quality started to go downhill as I increased the ISO setting. Increasing the ISO also increases the noise, i.e., graininess, of the shot. What I’m gathering is that it’s best to keep the ISO fairly low for a better quality shot.

I still haven’t really wrapped my head around the meaning of ISO, but I imagine the more I practice the more it will make sense to me.


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