The need to use a high ISO (for example, ISO 400, 800 or even 1600) just because you want to freeze the action before you in exacting sharpness is a myth! Yes, camera manufacturers are making some great strides in noise reduction. In particular, Canon and Nikon, the two industry heavyweights, have several digital camera models that deliver some truly low to moderate noise levels at the high end of their ISO spectrum, from 800 to 2400.
But with the promise of fine grain at these high ISOs its easy to become seduced and some of you might even think that you can now say good-bye to your tripod--yikes! Here's why you shouldn't be seduced by High ISO's.
ISO 100 action: With my tripod mounted Nikon D2x set to 100 ISO and my Nikon 70-200mm f/2.8G lens set to f/8 at a 1500 second, I froze the waves pounding on the rocks and still had enough depth to get the Golden Gate Bridge in the background. In this case, I wanted depth of field and got it at f/8, but at ISO 100 I was also assured of optimal overall image quality.
In action photography, if you expect to record--in exacting sharpness--the power of an ocean wave slamming hard against the rocky cliffs or a motocross racer flying over the rain-soaked hill, you will need all the ISO sensitivity you can get, right? Wrong! Just because ISO 400 lets you use a shutter speed that's twice as fast as ISO 200 and four times as fast as ISO 100, it doesn't necessarily mean the quality is better. Why? As you increase sensitivity, overall image quality gets worse.
Noise, also called grain, begins to be a real problem in DSLRs whenever you use a high ISO such as 640, 800, and beyond. Grain affects overall sharpness and even color and contrast. In addition, at higher speeds you often end up using smaller lens openings, which, increases the overall depth of field (sharpness from front to back) and this, in turn, makes the noise that much more apparent. And even if your camera promises noise reduction, the increased depth of field could introduce too much distracting background detail.
ISO 100, again! At a pool in Cancun, Mexico, my daughter posed under a small waterfall that sent down a gentle cascade of water into the pool. Hand-holding my Nikon D2x and Nikon 70-200mm f/2.8G lens, and with the ISO set to 100, shot this at 1/250 second and f/10.
Bryan Peterson is a widely-published photographer and a successful commercial photographer for over 30 years. He has photographed annual reports, corporate brochures and advertising campaigns for a diverse range of clients including Kodak, UPS, Intel, Microsoft, and Citibank. The most recent of his popular series of creativity and exposure books is "Understanding Shutter Speed: Creative Action and Low-Light Photography Beyond 1/125 Second." See his work at http://www.bryanfpeterson.com.