SEATTLE -- They're showing up in many places across the Northwest: Local government's traffic version of "Candid Camera".

Lakewood was the first five years ago. Seattle unveiled its system last summer.

Known as red light cameras, they automatically take photographs of the license plate of every car that enters an intersection on a red light. The registered owner of the car is then sent a ticket in the mail.

We watched what can happen during such a violation; a crash, captured in real-time video from a red light camera.

The technology was applauded by many drivers we spoke to.

“I guess you should pay attention to the road. I think it’s a good thing,” said one driver.

But it smacks of Orwell's "Big Brother" to others.

“You lose a little privacy with every camera that goes up. It’s just over the line,” said driver Ken Keesee.

Some product manufacturers want to take advantage of that resentment. For around $25 a can, they offer special sprays they claim will make a license plate invisible to these cameras by reflecting the flash back to the camera.

They're produced under various names. One of the best known is called Photo Stopper, made in Canada and widely available on the Internet.

We decided to put it to the test, with help from the Auburn police department traffic division, led by Sgt. Mark Wentworth, a 28-year veteran.

Auburn is one of the latest Northwest cities to install red light cameras at various high-traffic intersections in town.

The traffic division temporarily shut down one of those intersections for our test.

We carefully followed the directions on the can, spraying several light coats over three different license plates; a marked police car, an unmarked police car, and our news vehicle.

After waiting for it to dry as instructed, the test was on.

Sure enough, the traffic cameras flashed every time one of our test cars entered the intersection on a red light.

Later, we watched as Sgt. Wentworth showed us the results.

The cameras clearly captured the license plates of each vehicle, including our news car.

“Going through the intersection on a red light, and the license plate, we’ll get a good look at it and you can see it’s legible. There’s no difficulty in reading that whatsoever,” said Wentworth.

Even the company doesn't seem to have much confidence in Photo Stopper.

It told us the "manufacturer makes no representation or warranty regarding the effectiveness of this product."

And Sgt. Wentworth's opinion of products like this? He advises drivers to save their money.

“It’s pretty obvious that it does not work,” said Wentworth.

“We figured out which product to use, and that would be black paint. And that would probably obscure the license plate,” he said.

The success of these cameras in catching red light violators means they're here to stay. In fact, more and more jurisdictions are spending hundreds of thousands of dollars to buy them.

Right now in Washington, only a handful of cities have red light cameras in operation right now.

But there are a lot more who either have them on order, or plan to install them soon.

Sgt. Wentworth said the goal is not to make money or spy unfairly on motorists.

“We want to reduce the number of traffic accidents at these intersections, as well as change drivers’ behaviors,” said Wentworth.