Show Me The Light! Understanding ISO

One of the great advancements in the conversion from film to digital photography is the ability to change the ISO, or film speed, WITH ANY PICTURE.  With film, photographers were stuck with an ISO, or ASA, for 12, 24, or 36 exposures.  Today, a camera’s sensitivity to light can be changed with the push of a few buttons, allowing advantages that previous photographers could only dream of.

ISO, or International Standard Organization, is a group of people that get together to determine the standard measurements for the world.  For photography, they determined what qualified any certain film’s sensitivity to light and gave it a numerical value. Most 35mm photographers used 100, 200, or 400.  Here in America, we have our own “standard” as well, ASA, or American Standard Association, so you may of heard film called “100ASA.” Digital cameras are sold all over the world, that’s why ISO is used instead of ASA.

For photographers, changing the ISO setting on your camera allows you change the camera’s sensitivity to light. In lower light, you can turn the flash off and shoot in existing light by raising the camera’s ISO number.  Auto ISO usually defaults to a lower number and the camera fires the flash.  With the flash intentionally turned off, and the ISO number set higher, you will have the ability to take pictures indoors, given there’s enough light to get a fast enough shutter speed for a correct exposure.

Next installment in the series:  Changing Your ISO: Pros and Cons

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ps.  I hope everyone is enjoying the info, the groundwork is almost finished.  It’s great to see people commenting, tweeting, and recommending on facebook, thank you!