The last of the three basic photography principles is ISO and that’s what we’ll be going over today. And the good news is that it’s super easy to understand. And to make it even better, besides just applying to DSLRs, a lot of point and shoot cameras have adjustable ISO settings too!
Your ISO setting determines how fast your digital sensor “picks up” the light coming into the camera, and works in combination with aperture and shutter speed to determine your exposure. It’s a carry-over from the pre-digital days of film speed. The lowest setting is almost always 100 and can go all the way up to 6400 or more. A lower ISO number (100 for example) produces a clearer, smoother, cleaner image but requires more light to do so. So you will need to be in a very brightly lit area. A high ISO number (1600 for example) needs less light to capture the image, but the image will be grainier the higher you go. So you can be in a dark area and will still be able to capture your image, but it will have some amount of grain.
This first photo was taken outdoors with plenty of light, so I used a low setting of ISO 100 so I could get the clearest picture.
The second photo was taken indoors and at night (no flash) so there was very little light and I had to use a much higher ISO of 1600. You can see that there is some graininess to the image.
The newer your digital camera, the higher ISO settings it’s likely to have, and the less graininess as well.
A very easy way to understand ISO is the “worker bees” analogy. Think of your ISO number as your number of worker bees, and those bees’ only job is to buzz around gathering light for your photo! If you are in a dark area, you’ll need a lot of bees to help you get enough light for your picture, so you need a high ISO number. If you are in a very well lit area, you won’t need much help getting light, so a small number of worker bees will do the job and you just need the lowest ISO number (100).
So, that’s it! Totally easy! So once you have your aperture and shutter speed set the way you want, just try to keep you ISO set at 100. But if your photo is too dark you’ll need more worker bees gathering that light in for you, so increase your ISO until you can get the correct exposure!
Being able to adjust your ISO is awesome because it allows you to avoid flash use in low light conditions! I avoid using a flash whenever possible because it creates yucky harsh light and sharp shadows. You will get much better images by increasing your ISO instead, even if it does add a little grain. Most of the time in the newer, nicer DSLRs, the grain is almost unnoticeable!