Camera Lesson #3

What is ISO?

I have a handful of friends who own cool cameras, have a good eye, and a little knowledge. I have to admit they take some great images. However, they openly confess that they get stuck on things like shutter speed, aperture and ISO.

This week we are going to focus on ISO. Remember that I am keeping this very basic…these are not exact definitions from Wikipedia, but my version of the terms, and more importantly what they can do for your images.

With a film camera an ISO is an indicator of how sensitive a film is to light. This is measured with numbers. I am sure you have seen them. Have you ever purchased a disposable camera? You would have noticed these such numbers: 100, 200, 400, 600, or800.

The lower the number, the lower the sensitivity to light, so if you are going to shoot outside in bright light you only need an ISO of 100 or even 200. If you are going to attend an event that is inside, and chances are there will not be much light you would want an ISO of 600 to 800.

In digital photography ISO works much the same, however since there is no film involved this number is the measure of how sensitive light is to the camera's image sensor. The same rules still apply.

ISO at 100


ISO at 800


Another thing to keep in mind when choosing your ISO setting is the grainess of your image. The lower the number the finer the grain, and the higher the number you will notice what photographer call noise. So while 100 will give your image a smooth look, the higher the numbers can make your images look grainy, or when shooting digital this seems to come off more as smudged or murky.

So why do you need to know this you ask? Well consider these things when setting your ISO.

How much light is available to you? If you have lots of light then set your ISO low for a smooth clear image. If there is not much light bump up that ISO.

What are you shooting? Is your subject in action? If you need to stop motion then consider a higher ISO. However this is not nearly as effective as setting your aperture and shutter speed which we will touch on in the next couple of weeks.

Do you have a tripod? Depending on your lighting situation if you don't have a tripod you might have to shoot at a higher ISO to reduce the chance you might move when taking the picture and cause a blur.

Do you want some texture to your image? If you do desire that sort of grainess then try working with a very high ISO. Although this is much harder to do accomplish with a digital camera.

So break out that camera manual and look up how to set your camera's ISO setting. Play around and take notice of what a big difference this single setting can do for your images.