Sifting the Light: A Look at Lens Filters

Did you know that Ansel Adams used a lens filter in virtually all of his photographs? It's true. If lens filters can do wonders for black-and-white photography, just imagine what they can do for your videomaking.

Lens filters offer a simple way to get better images. These wafers of glass can soften the face of a bride, fake a sunset at high noon or add sparkle to the chrome on a vintage car.

I asked professional videomaker Myron "Buzz" Buzzini to help guide us through the world of lens filters. With 30 years of image-gathering experience--in both photography and video--Buzz was the perfect man for the job.

Buzz is a firm believer in the power of lens filters. He first used them with film, but didn't forget their usefulness as he made the transition to video.

On a bright Northern California morning, Buzz visited my office with a big bag of filters. We pointed my camcorder out the window and experimented with each one. In the article that follows, we'll share some of the insights that Buzz and I discussed that morning--insights that could help any videomaker in their quest for high-quality images.

According to Buzz, "A lens filter is little more than a piece of glass that attaches to the front of a camcorder's lens." Two basic types of filters are available: round filters that screw onto the front of the lens, and square filters that slide into a special housing attached to the lens.

The round variety is available in many different sizes. Make sure the lens filter you purchase will fit your camcorder's lens--not all camcorders have threads the same size. Generally speaking, palm-sized camcorders have smaller lens thread sizes, and full-sized camcorders have larger sizes.

Common camcorder lens thread sizes include 34, 37, 43, 46, 49, 52, 55 and 72mm. The thread size is often marked on the front of the lens. If you can't find it there, check the specifications page of your owner's manual; it's typically listed under "lens diameter."

Square filters that slide into a special holder--called a matte box--offer an advantage over the round variety: the filters are all the same size, so only the matte box need be fitted to a particular camcorder lens. This aspect is handy if you have two different camcorders, or even a camcorder and a 35mm still camera. You simply buy a matte box for each camera, then use the filters with either unit.

Both the matte box and round filter systems allow a videomaker to use multiple filters. With the threaded type, you simply screw one filter onto another. With the matte box variety, just slide another square filter into the housing.

With Buzz's help, we'll sort through the different types of lens filters and explore applications for their use. Let's start with basic filters and work our way to the more exotic species.

"If you only have one filter, make sure it's a skylight filter," Buzz says. "And keep it attached to your lens, always."

To the human eye, a skylight filter (also called a haze or UV filter) looks like a clear piece of glass, but don't be fooled. This filter does its magic by reducing the ill effects of both ultra- violet light and atmospheric haze on an image. Equally as important, this filter will protect your expensive camcorder lens from fingerprints, dust, grime and damage. When you buy a new camcorder, get a skylight filter, attach it and leave it attached--permanently.

Neutral density (ND) filters reduce the amount of light that enters a camcorder's lens. They prevent exposure problems in very bright scenes--like a white polar bear on snow bank on a sunny day, for example. Available in various densities, these filters work like a pair of sunglasses.

"Neutral density filters are great if you want to blur the background of a portrait-type image," says Buzz. To do this, simply focus on your subject with a neutral-density filter attached to your camcorder, and--just like magic--the background obscures into a pleasant fuzzy smudge. The filter forces the camcorder to open its iris wider, which reduces the depth of field, leaving the background out of focus. Naturally, this works best when the background is some distance away from the subject.

A polarizing filter eliminates reflections from shiny surfaces like water or glass. These filters rotate in a specially designed housing; the videomaker simply looks in the viewfinder and twists the filter until the reflections diminish. It's quite an amazing effect, when you see it for the first time. They really work.

Polarizing filters are also great for darkening the sky while making it appear slightly bluer.

Color correction filters perform the same function as your camcorder's white balance circuits; they correct the color temperature of the incoming light so your colors will look right, indoors and out. Since all camcorders now include white balance circuits, there's not much need for these filters in videomaking. They're still commonly used in film cameras, though.

Creative uses for colored filters abound. After all, they're available in almost every color of the rainbow. For example, a blue filter helps simulate a moonlit night; a sepia filter adds an old-time, historical look to an image. Have fun, and experiment with plenty of different colors.

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