Tuesday, July 24, 2012
Solutions: Polarizer Basics
How to get results with this must-have filter
Polarizers are best used with normal to telephoto focal lengths. Avoid using them on wide-angle models because you'll get uneven effects across your frame. The polarizer relies on a phenomenon called Brewster's Angle. Sir David Brewster was a Scottish physicist, and you can look up everything you ever wanted to know about Brewster's law at Wikipedia. For photographers, the upshot of Brewster's work lies in giving us a simple tool to predict how a polarizer will affect the scene. That tool is your thumb and forefinger. Point your forefinger at the sun and point your thumb straight up (like you're making a gun with your hand). As you rotate your wrist, keeping your forefinger pointed at the sun, everywhere your thumb points is where the polarization will be most pronounced. You then can rotate the polarizer itself to get the strongest effect. Look through the viewfinder or use Live View to see the image on the LCD to make precise adjustments.
Best Lighting Conditions For A Polarizer
High noon usually isn't the best time to use a polarizer, but as the sun gets lower on the horizon, it can make a huge difference. Sidelit photographs show darker skies and better color saturation. This makes perfect sense when you consider Brewster's Angle. A lot of novice polarizer users, however, think that when you're dealing with overcast conditions, a polarizer is useless. This couldn't be further from the truth. Overcast days are ideal for polarizers because they cut the reflections that rob your scene of color saturation. If you're including that overcast sky in the frame, the polarizer won't have the same darkening effect that you'd see in a blue sky, but the filter does wonders for saturating the colors on the ground.
Anytime you're shooting water, whether the surface is mirror-smooth or rippling and choppy, a polarizer can make a huge difference by cutting glare. When you're photographing a smooth lake, for example, rotate the polarizer, and you'll see the glare disappear and you can see underwater. This is useful when you have something just beneath the surface that you want to show. If there's nothing but mud, consider leaving the glare and reflection. In disturbed water, the polarizer will remove the distracting glare from the wave tips. Again, rotate the polarizer to see the effect as you're composing, and pay particular attention to the sky to be sure you're not making it uneven.
Most pro nature photographers will tell you straight away that anytime you're shooting a rainbow, use a polarizer. Try it, and you'll immediately see why. The colors in the rainbow, which can be weak and ill-defined, suddenly transform into rich hues. As you rotate the polarizer on your lens, you'll notice that the rainbow will disappear in one position, and as you rotate, it gradually will become stronger. Keep rotating, and it disappears again. Show your kids. They'll be amazed.
A pro technique for high-contrast conditions is to stack a polarizer and a grad ND filter. You can get complete control over your exposure, as well as the benefits of cutting glare and increasing color saturation. Simply darkening a scene doesn't create nearly the same effect.
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