Camera basics: shutter-speed, aperture and ISO · by Simon Mackie
ISO
The ISO of your film or sensor is a measure of how sensitive it is to light. “Normal” ISO, for taking shots outdoors on bright sunny days is 100. If you’re shooting indoors, or you’re shooting, say, sports and you want to use a high shutter speed, you may need to use a higher ISO (400 is common for sports photography). ISO goes in a doubling scale too: 50, 100, 200, 400, 800, 1600, 3200. Again, each increment relates to a doubling or halving of the sensitivity to light, so also equals one stop.
On modern digital SLRs you can often increase the ISO to 1600 or even 3200. The unfortunate trade off is that using a higher ISO introduces noise (on digital cameras) or grain (when using film).
Noise or grain is usually unwanted. I say usually because some traditional black and white photographers use grain for creative effect – I quite like the image above. On modern digital SLRs, noise usually only becomes a problem at higher ISOs such as 800 and above, but it varies from camera to camera.
One of the real advantages of digital cameras is that you can change ISO on the fly – you don’t have to rewind the film and put a new one in if shooting conditions change, which is very convenient.
OK, that’s it for our whistlestop tour. I hope that you found this introduction to shutter speed, aperture, and ISO useful!
commenting closed for this article
Exploring the Canon 350D/Rebel XT custom functions The Tilt-Shift Miniature Fake Technique in Photoshop CS: A Simple How-To