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ISO: Perhaps the Biggest Difference Between Film and Digital

In many ways, digital photography is merely a variation of film photography, but there are some big differences and ISO is one of them. ISO is the digital equivalent of film speed. When I shot film, I rarely used an ISO faster than 200 and never faster than 400. With today's digital cameras, I rarely use an ISO below 500, regularly use 800-3200, and occasionally use 6400. True, I use high quality gear (Canon 7D and 1D Mark IV), but even moderately priced point-and-shoot cameras can produce quite good images when used properly. (However, part of what you are buying when you purchase more expensive photo equipment is higher quality sensors and faster autofocusing lenses.)

This ability to use quality, high ISOs has allowed shooting subjects that were not realistic with film. For example, I have photographed Bald Eagles forcing Ospreys to give up and then catch their fish, Northern Harriers as they cruise by the hawk watch, Cooper's Hawks patrolling the dunes, Purple Martins hawking insects, and Yellow-shafted Flickers and Palm Warblers during their morning flights.

You need a high ISO to capture such images because they require very fast shutter speeds, at least 1/2500 of a second, and preferably faster. High ISOs also reduce out of focus images because your shutter is open for a very brief time. Not all of my shots are keepers, but at the price of pixels who cares. 

Mike Hannisian

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