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Saturday, September 1, 2007

Seeing in Slo-Mo

How to get motion blurs that will add a new dimension to your photography

The Pan Blur: Long Exposure, Moving Camera

A great way to photograph a subject moving across the scene is to use a slow shutter speed and pan the camera to track the subject. The slow shutter speed will blur the background into "speed streaks" that emphasize the subject’s speed, while the pan keeps the subject reasonably sharp. Good subjects for this technique include racing cars, running wildlife and birds flying across terrestrial backgrounds (birds against a plain blue sky won’t show a blurred background, since the background sky is all one tone).

It takes some practice to be able to do pan blurs well. Good practice subjects include cars driving by, dogs frolicking, birds flying and kids playing. Stand facing the spot where you want to photograph the subject, turn at the waist toward the approaching subject, pick up the subject in the viewfinder, track the subject with the camera by rotating at the waist and trip the shutter as the subject arrives at the desired point. Be sure to follow through and keep tracking the subject as you shoot; if you stop as you trip the shutter, the subject will blur.

You also can pan the camera horizontally or vertically across a static scene, such as colorful flowers or a stand of trees, to produce interesting abstract renderings. Try this with the camera on a tripod and handheld for different effects.

As with stationary camera blurs, the exposure duration required to produce the best pan-blur effect depends on the subject, how fast it’s moving, how far it is from the camera, whether it’s moving toward the camera or across the frame, the lens focal length and your personal preferences. Again, try a variety of exposure times and see which work best for you with a given subject. I like exposure times of 1/4 to 1/60 sec. for living subjects, and 1/15 to 1/125 sec. for racing-car pans. For pans across static scenes, try 1/4, 1/2 and one sec.

Some image-stabilizing systems can be used for panned shots, while others treat the panning motion as something to be countered; with the latter, unsharp images will result. Check the manual for your lens or camera to see how the stabilizer should be set for panned shots. That said, the lens I use most often has two stabilizer modes, one for normal shooting and one for panning, and in nearly 10 years of use, I haven’t noticed a difference.

The Zoom Blur: Still Subject, Stationary Camera, Moving Lens

You can produce an interesting blur effect by zooming a zoom lens during a longish exposure. For this technique, I like exposure times in the 1- to 2-sec. range because they give me more time to control the zoom effect, but exposures as short as 1/30 sec. can work. Experiment a bit to see what works best for you. It’s easier to work with the camera on a tripod, but you can try some zoom blurs handheld as well (push-pull zooms are better than rotation zooms for handheld zoom blurs). Note that most compact cameras don’t allow you to zoom the lens during an exposure; this is an SLR project.

You can zoom from wide to telephoto or from telephoto to wide; each produces a different effect. If you pause for half the exposure duration and then zoom, you’ll get an identifiable image of the subject as well as the zoom streaks.

Zoom blurs work best with high-contrast subjects; flat scenes yield murky images. Backlit flowers make good subjects; frontlit meadows do not. I’ve found that 3x and 4x zooms work best for this technique. If you have one of the popular extreme-range zooms, you might try just using a portion of its focal-length range instead of the full range. Experiment with different exposure times and zoom rates until you find your sweet spot.

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