Drivers Try an Anti-Photo Finish

His test finding: "The flash went off behind me, but I've never received a ticket."

The Denver Police Department, at the behest of Fox News, conducted a road test two years ago and found that PhotoBlocker was effective, plate covers less so. Similar results were found by TV news programs in Great Britain, Australia and Sweden.

Five Washington area police departments declined to or didn't respond to requests that they conduct roadside tests for The Washington Post. Those who responded said they didn't have time and wouldn't want to promote a product that may be illegal or interferes with law enforcement.

"We'd have to shut down the streets and traffic, and all of our red-light cameras are at major intersections," says Capt. David Mellender of the Fairfax City Police Department, which uses seven red-light cameras. "And if it does work, we don't want them to know about that."

Fairfax County has 13 red-light cameras and plans to add two more by year's end. Bud Walker, an officer with the county's police department, says a field test "could be seen as an endorsement, and as a public institution we can't do that."

Despite the television news tests, there's little consensus about the effectiveness.

Ray "Radar Ray" Reyer, whose online firm Radarbuster.com sells Photo Fog and PhotoStopper, says roadside and weather conditions and camera angles can affect clarity. And the "flash-back" sprays have no effect against digital cameras that don't flash, like the ones Howard County recently began installing.

"We would safely estimate 75 percent effectiveness," says Reyer, a retired 20-year veteran of the Maricopa County, Ariz., police department who markets mostly radar detectors.

Speed Measurement Laboratories -- consultants to police departments and radar and radar-detector makers worldwide -- has tested most products designed to defeat photo enforcement, including car waxes and stealth sprays that claim to make cars "invisible to radar," photo-flash devices designed to flash back at cameras and the high-gloss tag sprays.

"There's a lot of good people in the industry who are honest and a lot of charlatans. But it doesn't work, that's the bottom line," says Carl Fors, owner of the Fort Worth company.

The bounce-back-the-flash concept does work sometimes, he says, but only on positive images traffic cameras produce. "If we reverse the image, go to a negative image, we can read every letter on a license plate," he says.

Fors says the firms that make and operate radar camera systems and analyze the photos for municipalities routinely check negatives where license plates look unreadable. "Going to the negative image is no big deal," he says.

PhotoBlocker's Scott concedes that adjusting the images can "sometimes" reveal the tag numbers, but "these companies will just throw out anything that's questionable. They don't want to have to dispute it in court and it's not cost-effective for them."

Richard Kosina, director of engineering at Affiliated Computer Services, maker of most of the photo-radar cameras active in the District, Maryland and Virginia, says magnifying the image or adjusting brightness and contrast to make glared or blurred plate numbers legible is easy.