You're shooting your son's soccer game and it's dark and dreary. At ISO 100, the fastest shutter speed you get is 1/125 second at f/4. Not fast enough. What to do?
If you were to shoot at this exposure you run the risk of recording blurry action. You could easily set the ISO to 400, 640 or 800, but that means noise, and you are all about razor-sharp images, with the best color and contrast.
What can you do? Shoot RAW! With RAW you can deliberately record images that are two stops underexposed, and than correct these normally bad exposures in post-processing. It's like push processing that we used to do in the darkroom. You can correct these images so well, in fact, that no one will notice that they were ever too dark to begin with!
Don't believe me? Sounds like a really bad idea?
Let's go back to your son's soccer game. Instead of shooting at f/4 and 1/125 sec, shoot two stops underexposed, (f/4 at a 1/500 second) and you will record your razor sharp, action-stopping images anyway. Yes, they will be too dark in your camera's monitor. Don't panic. When you return home, you can bring these once too dark to see exposures into the light and once again look like the hero using Adobe Photoshop, Elements or Lightroom's RAW editing tool.
Too dark: Kayak competition in Prague, shot at ISO 100. My meter said f/5.6 at 1/800 sec., but I wanted more depth of field. I overexposed by two stops, for an exposure of f/11 at 1/800 sec.
Histogram says it all: On Adobe Photoshop's RAW editing screen, here's how the image came up, with automatic settings making it a little brighter.
Pump it up: I overrode the default exposure reading, setting it instead to to +2.00, making up for the deliberate underexposure and rendering a correct exposure.
Look ma, no artifacts! Shot at ISO 100, underexposed 2 stops, virtually overdeveloped by 2 stops, final result: If you didn't see the original, would you believe this image was saved from the dark ages?
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.