Bruce Wayne's device

Question

So in that movie, when Bruce Wayne makes his public appearance at the charity ball, when he gets out of his car, cameras start flashing and he has something in his hands and he presses a button when renders all cameras useless. What is that device and how does it work? Is it like a mini EM pulse? But that would effect all electronics in its range. In the movie it is implied that everything else like other bulbs/lights work fine. Its only the cameras that don't work all of a sudden.

And is it on his motorcycle too? Because the cops complain about the lights when he's in the tunnel and the lights seem to be going with him. As he moves away the lights come back on.

Answer 1

Lasers

There are many devices already on the market that can disabled digital cameras via a laser. The laser over loads the digital sensor (either temporary or permanently) and it's no longer able to take pictures.

There are several over the counter lasers that are strong enough to do this. Including cheap pointers used by teachers on white boards. A direct hit to the camera's lens will disable it.

I found an article on the subject. Camera Zapper

In the film Tron Legacy the character Sam Flynn disables a security camera in a hallway using a hand held laser.

Can It Be Automated?

There already exists automated systems that can discover cameras via a flash feedback. The device uses an IR flash and any cameras pointed in it's direction will reflect back the flash. The system can then target the camera and strike the sensor with a powerful laser to disable it.

This has already been used by rich people to protect their privacy. Yacht Comes Equipped With Laser-Powered Anti-Paparazzi Shield

Is Batman's Device Real?

No I don't think so. He uses a small tiny hand held device to disable multiple cameras in one shot. In addition, the camera's appear to also be without power. A laser would only disable the sensor and only temporary.

Still, the technology is base upon things in the real world.

Answer 2

Well In the motorcycyle chase he used an EMP gun.

When used, Batman can take down enemies or operate electrical equipment from a distance when shot at. We don’t know of any sight more intimidating than that of Batman staring you down while brandishing a gigantic electrical rifle. Here is a photo of the gun.

Batman using EMP gun in Dark Knight Rises

EDIT- Further surfing revealed it is the same thing which is capable of turning off the cameras also.

The EMP rifle releases an elctromagnetic pulse which is capable of disabling any electronics within a given range. This includes camera feeds, security systems, cell transmissions, electric vehicles, and anything else Batman might wish to disable.

So like you guessed, it might be a miniature of the EMP gun which he used to shut the cameras. Also the EMP guns can be pointed to stuffs very sharply, we have seen that in the motorcycle chase. So if there is a mini-EMP it is more easy to point it to a smaller area with cameras only.