Been caught flashing?
May 6, 2006 9:51 PM   Subscribe sell The PhotoBlocker Spray, The PhotoShield Cover, and The Reflector Cover. Has anyone purchased any of these products, used them, run a red light, been flashed by a camera, and not received a ticket?

Or in other words - does anyone have proof that any of them work? This article suggests not....
posted by forallmankind to Travel & Transportation (16 answers total)
I can't imagine how this could possibly not be a rip-off.
posted by Rhomboid at 12:16 AM on May 7, 2006

All but one of these use a hypothetical flash to make the number disappear. In the middle of the day no flash is needed to photograph your plate. I'm not all that familiar with the technology, but even at night your average flash does not reach that far and would be useless. Infra red? I'm not sure. does it have the resolution for this? A more powerful visible flash would potentially blind other drivers. No, I dont think the police cameras depend on flash, so this stuff is probably useless. If anyone else knows differently, please speak up.
posted by ScotchLynx at 12:45 AM on May 7, 2006

Where I live (Australia) both red-light cameras and speeding cameras DO use flashes at night. I'm not sure how the flashes differ from "normal", but there doesn't appear to be any danger of the flash "blinding" other motorists.
Regarding the original question, I have a friend who bought something very similar to The Reflector Cover. He was never photographed running a red light, but was snapped speeding (at night, camera using flash) a few times - I've been in the car twice when it happened. He never received an infringement notice regarding these instances of speeding. He credits the reflecting thing he had fixed to plates, but it's worth noting that there are many reasons for no offence being recorded despite a photograph being taken (calibration and margin-of-error issues, "accidental" obscuring of plates by other cars etc. etc). I've been "flashed" about ten times and received only five or six tickets/photographs and have never done anything to my modify my plates.
The point of all this rambling is that my friend swears by The Reflector Cover-type things (though the cops made him remove them... eventually). I'm not so sure myself
posted by bunglin jones at 1:20 AM on May 7, 2006

They flash during the day too - I often see them going off on a highly controlled road near me. I presume the flash is as much an exposure as an illumination thing?
posted by A189Nut at 2:11 AM on May 7, 2006

I don't see how a simple spray could disperse the light effectively. That said, this question has prompted me to think about the methods by which traffic cameras work and the properties of light and cameras that might be manipulated to work to your advantage.

Ever photograph someone in front of a mirror with a flash? What happens? The part of the picture where the camera's flash is reflected back towards the lens gets blown out because the camera calculates distance and assumes non-reflectivity and thus is expecting a certain exposure. With "normal" objects, light is scattered in all directions; with reflective objects, the reflected light is highly directional.

Almost all bare-bulb flashes are extremely directional: this is the reason why when you take a picture of a person standing in front of a wall, you get an ugly, well-defined shadow of that person right behind them. When you put a softbox or diffuser on the flash, you change the effective size of the light (larger effective light size == softer shadow). The sun is an extreme example of a highly directional, single-point light souce. A cloudy day, on the other hand, is like a giant softbox, with light waves coming at you from all directions.

So how does this relate to traffic cameras? Well, if you could scatter the light, you could block the license plate number. But that's no good: a translucent screen will scatter the light just fine, but then nobody will be able to read the number. In fact, I think you'll find most light-scattering techniques ineffectual because the simple fact is, if the camera can't see it, the cop probably can't see it either. No dice.

BUT. A cop's eyes are not the same as a camera's eyes. We can use the inherit inefficencies in the way a camera reads exposure to beat the traffic camera. Here's how:

Your eyes are constantly adjusting the amount of light that hits your retina. They do it so fast that it's difficult to guage just how bright something is if it falls within the "normal" operating parameters of our eyes. If it's too bright, your iris can't close your pupil small enough, thus "It's a bright day, isn't it?" Also, if your eyes are suddenly exposed to a bright light after being in a dark room, they can't react quickly enough, so more light comes in than your retina is happy with, and again, "Wow, sure is bright outside, huh?"

A camera's main Achilles Heel is that it is static. Sure, it can adjust for light sensitivity, but at a certain point (when the shutter is triggered), the aperture is locked to an automatically predetermined exposure. It adjusts for ambient light + camera flash to determine this exposure.

What it would not expect, however, is for a hypothetical burst of localized light on... say... a license plate. The kind of hypothetical burst of localized light that might come from... say... another flash. If you were to trigger a flash at the same time as the camera's flash, you would completely screw up the exposure for the traffic camera. Much like the photo of someone in front of a mirror, the traffic camera can only cope with a very narrow exposure latitude. Add a few stops of light to the mix and suddenly that part of the picture turns to white.

But how to trigger it? The same way photographers' flashes trigger each other: a photovoltaic cell. In a nutshell, a photovoltaic converts light into energy (like a solar cell). When it recieves more light, it outputs more energy. Ergo, if you were "listening" to the output, you could easily tell if someone just popped a flash off because the voltage would spike. This is how remote off-camera flash units work. One flash is connected to the camera, another is strapped to a pole a few feet away. When you snap a picture, the first flash goes off--this burst of light is what triggers the second flash to go off. Because light moves so quickly, this is more than enough time to get both flashes to register on your film (since most exposures are 1/60th of a second or so).

The problems I can see are:
  1. If it's daytime, your fucked. You only need ambient light to photograph a license plate during the day, which means no flash of light to trigger your own flash. I suppose you could wire up a REALLY BRIGHT light to shine on the plate when you go through a light, but it might be kinda obvious. :)
  2. If I'm not mistaken, traffic cameras take multiple exposures. That means you have to have a flash unit capable of recharging its power cells very quickly.
  3. It could be tricky to mount the flash in such a manner as to remain unobtrusive and yet still maintain its effectiveness. On the back of the car this is no problem: most license plates are recessed into the back a bit and have lights that already illuminate the area when your headlights come on. Unfortunately, this won't do you much good unless you don't mind driving through intersections backwards. The good news is that if you did decide to drive through intersections backwards, they'd never get your plate number! Suckas!
Anyway, this has been a fun mental exercise, and I apologize for the lengthiness.
posted by Civil_Disobedient at 2:44 AM on May 7, 2006 [1 favorite]

That's all very interesting in terms of the hypothetical, but the device under consideration here is just goo that you spray on, and is completely passive, so none of these considerations really apply. Not to mention that outfitting any motor vehicle with any kind of active strobe or flash is going to be illegal in almost any jurisdiction -- since not only might it potentially cause distraction to other drivers or temporary blindness, but that kind of thing is reserved for emergency vehicles anyway. So regardless of whether it would help you get out of a camera's ticket, it would be illegal and it would be hard to escape notice.
posted by Rhomboid at 3:48 AM on May 7, 2006

so none of these considerations really apply

I addressed the "goo" in the beginning. The rest was mere brain-play.

outfitting any motor vehicle with any kind of active strobe or flash is going to be illegal in almost any jurisdiction

Most likely.

since not only might it potentially cause distraction to other drivers or temporary blindness

Most likely not. The duration of the flash can be set to ten thousandths of a second (think Doc Edgerton), and localized to a very small area (your license plate). I sincerely doubt it would be noticed.

that kind of thing is reserved for emergency vehicles anyway

We're not talking about a giant flashing light on top of your car that's by design built to be noticed. Anyway, it would be illegal for the same reason radar detectors are illegal in some places in the States: because you're actively trying to defeat a method of law enforcement. Cops don't take kindly to that.
posted by Civil_Disobedient at 4:50 AM on May 7, 2006

"Made of a high quality plastic cover with light reflecting crystals, the Reflectorâ„¢ overexposes photo radar and red light camera pictures by reflecting flash back to the camera."

So, that one's supposed to be a retro-reflector. There are retro-reflective paints as well, so a spray-on solution might work equally well. I guess the little crystals act as corner cube reflectors, sending some large portion of the light from a flash straight back where it came from, thus confusing the camera. If it works, maybe it could be defeated by putting the flash some distance away from the camera.
posted by sfenders at 5:45 AM on May 7, 2006

These cheat devices are illegal in BC, if not all of Canada, and I can't imagine they're legal in your locale either.

And as they are red light cameras, intended to discourage you from running red lights, I pray to all gods and cops that if you put one of these on your car, you get your sorry ass busted from here to hell.

The yellow light means "stop if possible." You should never have to run the red light. I've come too close to being wiped off the face of this planet by asshat red light running asswipes to have any forgiveness whatsoever for the drivers.
posted by five fresh fish at 8:18 AM on May 7, 2006

The yellow light means "stop if possible." You should never have to run the red light.

These two sentences contradict each other. If possible is a very important clause--there are many instances when it would be dangerous to slam on your brakes (it does snow in BC, right?) The problem with traffic cameras is they have don't record context.

For instance, imagine you have two cars in opposite lanes approaching an intersection. Car A wants to turn left, but is waiting for Car B to pass before they do so. The light turns yellow. Car B finally passes. Does Car A continue the turn, or stay stuck in the center of traffic because, well shucks, the light's red?

Example two: you're in a small car, stopped at a light. There's a big rig in front of you, blocking your view of the light. The rig goes through the intersection, you follow. Too late, you see the light is yellow, and will probably turn red before you've left the intersection.

There are a hundred combinations of the above, where the intention isn't to break the law. The problem is that traffic cameras make people bad drivers, because they put an element of fear in your head when you should be thinking about the road. You shouldn't be thinking, "Car coming in opposite lane, car behind me tailgaiting, car in my blindspot, pedestrians crossing illegally, what is the best course of action? Oh yeah, this intersection has a traffic camera. Floor it or jam on the brakes."
posted by Civil_Disobedient at 9:33 AM on May 7, 2006

Response by poster: With all due respect fff, you live in the middle of nowhere, and I live in the center of LA. If you were to live here and do my daily commute home, you'd be aware of sections - through Beverly Hills on Sunset for example - where there are cameras ever other intersection and they go off like they're ADD on caffeine. I'm sure other LA drivers can attest to this.
posted by forallmankind at 9:39 AM on May 7, 2006

As a data point if you've ever taken a flash photograph at night in an urban area you can attest to how reflective most US license plates are already. They're designed to catch as much light as possible to make them easily legible in bad lighting. I think anything short of a mirror on the back of your car would fail from an exposure-confusing point of view.

I have seen video of the plastic covers (that resemble a flattened /\ over the numbers) obscuring half of the plate from certain angles. I suspect that that method may work at least some of the time.
posted by Skorgu at 10:20 AM on May 7, 2006

Mod note: morality issues concerning red light running can be taken to metatalk
posted by jessamyn (staff) at 10:33 AM on May 7, 2006

I can think of some exotic birefringent crystals or thin films that would function in certain conditions against specific incident wavelengths of monochromatic, coherent light to prevent or frustrate image capture from certain angles. But they would be quite finicky, and quite expensive. Definitely not something you could just spray on and hope for the best. The devices described above do not seem based on any clever optics - the plastic device shown just seems to be using a high refractive index to create some total internal reflection at the plastic/air interface for moderately large angles.
posted by meehawl at 6:46 PM on May 7, 2006

Sfenders, your guess of cubic corner crystals is inspired, but cubic corner crystals, as opposed to open cubic corners, which Apollo astronauts left an array of on the Moon, can only retroreflect light rays which get into them past reflective faces, and then only those that leave via the same faces they came in through. And, I think they would be more costly than what's actually used, which, as far as I know, are tiny transparent spheres.

These tiny beads are the source of the sparkles in reflective tape and paint. If the goop or the shields contain them, I think they could be effective, but only at night. License plates have them too, and they are the only thing that allow flashes which won't blind drivers to be able to pick up the plate-- so you can't move the camera away from the flash
posted by jamjam at 10:04 PM on May 7, 2006

only retroreflect light rays which get into them past reflective faces

The light that doesn't get through them would be useless for reading the plate number, so that would contribute to their intended purpose. Same thing for the more sensible tiny spherical reflectors. So my next guess is that normally only the white part of the plate is retroreflective, and that changing that is a large part of what makes it work, more than any increase in total reflectivity. So that would make it hard to defeat by adjusting the camera for exposure, and perhaps easier to visually detect at night by pointing your headlights at it.
posted by sfenders at 4:13 AM on May 8, 2006

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