The Orphan Child Called ISO
By: Chris Roberts

ISO wasn't easy to change on early digital cameras.

First, here's a quick definition: ISO stands for the International Standards Organization. What it really indicates is a digital sensor's sensitivity to light.

A low ISO is less sensitive and a high ISO is very sensitive.

Further translated: a high ISO like 3200 means that the sensor can capture a clear photo, even in low-light conditions. A low ISO like 100 requires a lot of ambient light for clear shots.

So why is this setting so often ignored? It's harder to sell the benefits of ISO (which is pretty confusing to anyone who is not a camera junkie) versus something simpler like speed (2 photos per second or 5 photos per second...which one's faster?).

Well, I'm here today to try to illustrate the benefits of ISO. It is a prominent feature on all of the latest digital cameras, and is something that you should be aware of when you're trying to take photos in available light.

Benefit #1 - Clear hand-held photos

Here's the problem: you're taking photos indoors on an overcast day. The only way that you can get a proper exposure is to slow down the shutter speed to 1/30 of a second.

The camera's shutter needs to stay open 1/30 of a second to let in plenty of light. Unfortunately, the longer the shutter stays open, the more likely your photo will turn out blurry. The blur is caused by camera shake when you hold the camera in your hands.

While blur is sometimes desirable to illustrate motion, most ot the time it's not the effect you want.

You really want to get a clear photograph, but there isn't enough ambient light. You think you're stuck with two options: use a flash, or attach the camera to a tripod so it's stable.

But here comes ISO to offer up a third alternative: set your ISO to 800 or 1600.

This boosts the light sensitivity of the camera's sensor, so you're not forced to keep the shutter open so long. With a shutter speed of 1/125 or 1/250 you can now hold the camera in your hands and get perfectly clear available-light photographs.

Benefit #2 - Atmosphere

As you increase the ISO on your digital camera, you also increase the noise in the photograph. "Noise" is the appearance of dots and specks, typically in shadow areas of the image.

Digital camera manufacturers have gone to great lengths to minimize noise, even at high ISO settings. This is due to benefit #1 above.

But sometimes you might want that noise in your photograph. Let's say you're taking shots on a foggy day, and the mood of the scene could really use some noise, to give the photo an old-time look.

Boost the ISO as high as it will go (usually 3200) and that noise will appear in your photo. In black and white, it really adds to the atmosphere and the quality of the image.

Benefit #3 - Fast shutter speeds

One of the best uses of a really fast shutter speed is to freeze motion.

If you take a lot of photos of sporting events, you need to be using shutter speeds around 1/1000 of a second or faster. There are not many days where there is enough ambient light to use these super-fast shutter speeds.

The only way that you will be able to catch all the action is if you increase your ISO. If you don't want noise in the photo, just increase the ISO enough to get the shutter speed you want. If ISO 400 will get the job done, then use that.

Summary

I hope that this brief introduction has opened your eyes to the usefulness of ISO settings on digital cameras.

I think that the ability to change ISO on the fly is one of the biggest advantages that digital cameras have over film.

With film you'd have to shoot an entire roll at one ISO setting before you could switch to another (or you had to have 2 cameras with different ISO films).

With digital you can change the ISO anytime, anywhere. It gives you complete flexibility and control over the photos that you take.

Changing the ISO setting does take some getting used to, and it's still not easy to do on some digital camera models.

I am sure though that once you start using it, you'll find yourself saying "Please, sir, may I have some more?"

Chris Roberts purchased his first digital SLR camera 3 years ago, and hasn't looked back. He continues to learn and write about new and emerging digital SLRs to this day on his web sites, the Digital SLR Guide and the Digital SLR Guide Weblog