Old film box. See the 100? That's its ISO.
ISO is the number that refers to the measurement of your camera’s sensitivity to light. The higher you set your ISO, the more sensitive your camera’s sensor will be to light.
- Outside in sunshine? Ratchet down your ISO to 100, or 200.
- Inside, or shooting in low light? Try ISO 600, 800, 1000.
ISO is an acronym that stands for the International Organization for Standardization. In the olden days, we had to buy film (see photo on right) with a particular ISO number depending on what type of photography we had planned (outside bright light, inside, sports, etc.). ISO 400 was a typical all-around film that we’d buy. In the olden days we were stuck with the same ISO until we shot the whole roll of film. Nowadays, with DSLRs, ISO is something you can change as much as you like.
The higher the ISO, the faster the shutter speed you can use. On most cameras, there’s a pronounced correlation between high ISO and how grainy your photo is. So you end up trading graininess (commonly referred to as “noise”) for the ability to shoot in lower light at higher shutter speeds.
Which ISO Setting Should I Use?
You can set your camera to automatically select the ISO. But that’s only good some of the time. Most of the time you’ll appreciate setting it manually. Read your manual to learn how. A general rule is to use the highest ISO you can get away with, to ensure a sharp photo.
- Another general rule of thumb is that the more expensive DSLRs will perform better at higher ISOs. If you’re using a high-end DSLR the resulting images shot at high ISO will produce less noise (graininess).
ISO, Aperture, and Shutter Speed are all interrelated. Read all 3 posts:
- What is ISO? (this article).
- What is Aperture?
- What is Shutter Speed?
