ISO...
Doing More Than Seeing in the Dark

Film has different "ASA" values, or numbers. The lower the value, the less sensitive to light is the film. Film speed ranged from roughly ASA50 to ASA3200.

A setting of 3200 is extremely sensitive to light, but often looks quite "grainy" in appearance. Generally, the more expensive the digital camera, the higher you can set the ISO while still producing a quality image.

For example, the Canon EOS-1Ds Mark III has been reviewed as producing decent quality images at 1600 and sometimes even at 3200; but for a 21MP camera that lists for $8,000, one would expect so (in addition to making dinner and cleaning windows).

For more affordable digital cameras (and it's not always price), we need to set our expectations a bit lower.

When we're done with this topic, you will understand:

• What ISO is, and

• Why it is important

What is ISO?

The range of available settings vary considerably, by camera make and model. For your less expensive cameras, a rating of 100, 200, or 400 is typical.

Medium range cameras may go up to 800, while the more expensive digital cameras on the market can go up to as high as 1600, or even 3200.

When a photograph is taken, some setting must be used. Knowing which is the best one to use in different shooting conditions can produce better results.

Why is Knowing About ISO Important?

For example, rather than the shutter being open 1/250th of a second in good light, it may need to stay open 1/60th of a second in dimmer light.

So why is this important? The major reason is this: The longer the shutter remains open, the greater the chance for camera shake

And camera shake will probably result in a blurred photo. So, by increasing the ISO setting, we change the camera's sensitivity to light.

If it's more sensitive, the shutter speed can become "faster" (the aperture stays open a shorter period of time), while still allowing the proper exposure of the shot.

Several photography terms are somewhat confusing (such as what is truly an affordable camera).

Another example is referring to a lens as fast or slow. When a lens is considered a "fast" lens, that means it's aperture can open wider than a "slow" lens. The greater an aperture opens, the more light can enter, and the less time the shutter needs to stay open.

While a slow lens may need to stay open 1/250th of a second for proper exposure, a fast lens may only need to remain open for 1/1000th of a second. Clear? I didn't think so.

When to Use Different ISO Settings

When capturing extremely bright scenes, such as on the beach, ski slope, or direct sunlight, use a low setting such as 100. On the other hand, at dusk, when it is overcast, or when shooting indoors... use higher settings such as 400, 800, or even 1600.

The big tradeoff - Speed vs. Grain

The only way to truly determine which is the highest setting you can use with your camera is to shoot dimly lit scenes with different settings, and determine the specific sensitivity where the resulting photo comes out looking unacceptable to you. For most non-prosumer cameras, 400 will be OK, but 800 and above won't be. But only you can be the judge.

One of the biggest secrets in photography...

This photo was taken at a setting of 800 hand held (sometimes a solid surface isn't practical) at 1/30th of a second. Before attempting this type of shot, experiment with different white balance settings, and check the shot afterward for sharpness.

Leave ISO and return to the Home Page