Rio Grande Gorge Bridge, photo by Harold Davis. View this photograph larger.

The Rio Grande Gorge Bridge, near Taos New Mexico, is a spectacular place to walk anytime, but particularly at twilight. Five hundred feet long, 650 feet above New Mexico’s Rio Grande river, this delicate steel structure, built in 1966, vibrates with every passing car. Here’s a view looking down the river gorge from one of the “balconies” in the center of the bridge.

After spending some time photographing from the bridge (and many of my photos were spoiled because vibrations rendered my use of a tripod futile), I decided to photograph the bridge itself. I stationed myself on the lookout beside the rest area on the west side of the bridge. It was getting too dark to take a normal photo of the bridge, so I decided to wait for cars so I could capture the headlights and tailights in motion on the bridge. You may have to view the photo larger to really see this.

This kind of exposure is always one part guesstimation, no matter how fancy the equipment one uses. With the camera on tripod, I tried a number of exposures with differing shutter speeds.

I tried to time it so the car would cross a good portion of the bridge during the exposure, but this timing was a bit tricky—because the behavior of the cars on the bridge, pretty naturally, was unpredicatble. Often, they slowed down on the bridge either to take in the view, or to be safe. And there wasn’t much traffic, in any case.

This exposure was at 20 seconds and f/16.

Not seen in the final image, a high fence to protect tourists from themselves and the Rio Grande gorge, covering the lower portion of the photo. I cloned it out in Photoshop, and also double-processed the RAW file to expose for the sky and the bridge.