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What is ISO?

How to Manage Light Sensitivity

Wondering what is ISO? In modern digital photography the term ISO refers to the sensitivity of your DSLR’s sensor to light. It’s taken from the Greek word isos, meaning equal.

What does ISO stand for?

So what does ISO stand for? It’s an abbreviation for International Standards Organization, which refers to the group that set the standards for film speed.

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Understanding ISO

Most digital cameras allow you to adjust ISO, and therefore the sensor’s sensitivity to light.

ISO settings generally range from 25 at the very lowest level, to 6400 at the top end of the spectrum. The sensor will be more sensitive to light at higher ISO settings and less sensitive to light at lower ISO settings. Most DSLR’s are set at ISO 100 by default.

Why worry about the sensor’s light sensitivity at all? Simply because in extreme light situations, when it’s too dark or too light for proper exposure, additional control measures are necessary. In these conditions, aperture and shutter speed alone will not be enough to create an acceptable image.

Benefits of Mastering ISO

• It allows you to continue shooting in low light without the use of a flash, whilst helping to avoid camera shake:

• It grants improved control over apertures and therefore depth of field; and

• It can boost the range of the flash itself.

If you’re wondering if you can just crank the ISO setting all the way up to the max and be done with it, hang on for a second! Increasing the ISO dramatically increases image noise in your photographs, which is hard to remove during post processing. Ideally, you should keep ISO as low as possible; only increase it slightly when you light is low.

Applications of ISO

* If you shoot directly at the sun or bright lights, a lower ISO and fast shutter speed are applicable;

* If you shoot indoors with ambient light conditions, a higher ISO will help you capture objects effectively in their natural light;

* If you shoot moving subjects outdoors in low light, for example at dawn or dusk, higher ISO levels will be helpful to freeze motion.

* ISO and flash can be complementary. An increase to the ISO can heighten the effective illumination range of a camera's flash. This can be a great help to DSLR's with smaller, top-mounted flash with limited range functionality.

Once you've experimented enough to establish a comfortable hold over ISO, challenging lighting conditions will become a breeze!

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Tips for Using ISO settings
Reader Post: 'It's important to understand that it's not just noise that increases with increased ISO settings. There are actually three issues that decrease ...