How to Choose Backup or Rear-view Car Cameras
License Plate, Wired, Wireless, Night Vision
Nov 12, 2009
Car cameras (CCTVs: closed circuit TVs) increase a driver's field of view, and therefore safety. While one camera can suit more than one application, drivers should realize that cameras are optimized for specific uses.
A camera (plus monitor) can cost from $80 to a few hundred dollars. Popular brands include Peak, Pioneer, Audiovox, Roadmaster, Voyager, VR3, 4UCam, XOVision, Shift-3, Clover, Bravo and Winplus.
How to Use Automobile Cameras
Vehicle cameras are used for:
- Backup safety: checking that there are no children or pets behind the car when reversing. This needs a wide-angle view camera.
- RV and truck rear-view: acting as a rear-view mirror when the vehicle is on the road. A camera that is too wide makes it difficult to judge distances: whether the car behind is too close for safety, whether there is enough space to safely cut back in from the overtaking lane.
- Trailer hitching: positioning the vehicle to hitch up a trailer. The camera is only used occasionally. It can therefore be battery-powered (no installation required) and temporarily stuck on to the vehicle or bumper with a magnetized base. The camera is removed after use, keeping it safe from thieves.
- Parking: judging distances to walls, drains and other obstacles. As with rear-view use, a camera that is too wide makes it difficult to judge distances.
Cameras typically have a horizontal field of view of 120 to 180 degrees. They wider the field of view the more the distortion: straight lines are curved (fisheye). Zoom and pan/tilt cameras are difficult or impossible to find. It's also probably not a good idea to distract the driver with too many controls.
Camera Wiring and Power: Reversing Only?
Cameras are spliced into the existing 12 volt DC (car battery) wires used by the car lights or other accessories (the camera draws only a few watts):
- Splicing into the reversing lights means that the camera will only be powered up when reverse gear is engaged.
- Some drivers prefer to use the parking lights circuit, so that they can have more control over when the camera is on.
- It is also possible to have the camera switch on when the engine is on (or when the ignition key is switched to ACC) by splicing into a suitable circuit. This is good for RV and truck rear-view use.
Automobile CCTV Cameras and Monitors
Cameras usually output standard analog color TV (NTSC or PAL) signals with a few hundred lines of vertical resolution (about 250,000 pixels total). Like webcams, they use small (1/4 or 1/3 inch) CCD or CMOS image sensors.
Night vision is available, with infra-red LEDs providing illumination for the camera. Other models depend on street lights or the car's own reversing lights and should be good enough for most purposes. One useful feature is the ability to reverse the camera image (mirror image) as this can appear more natural to the driver.
The monitors are typically color LCDs, with a screen from 2.5 to 7 inches in size (diagonal length). They can be mounted on top of the dashboard, on the air vent, on the windscreen (local laws may forbid this) or by the side of the rear-view mirror.
Wired Versus Wireless Vehicle Cameras
Wireless cameras are easier to install as a signal wire does not need to be run from the rear of the car to the monitor on the dashboard. The antenna is often built into the camera for simple one-piece installation.
Reception can be a problem, so some wireless cameras have a separate antenna on a wire. The antenna can be positioned for better reception but this complicates the installation. Some cameras are wired-only, and others have both wired and wireless connections.
Camera Mountings and License Plate Cameras
License plate cameras are mounted at the top or bottom of the car's rear plates (or frame), using the same screws as the plates. They are built into a small black plastic strip (like a watch on a watch band) and are small and unobtrusive.
Other cameras are clunky little units the size of a golfball, and are fixed to the bumper or the inside of the car (possible for RVs, hatchbacks and station wagons).
Do Backup Cameras Reduce Accidents?
A 2006 US National Highway Traffic Safety Administration report says that camera systems are the most promising aids to reducing backover accidents. The report does add the caveat that, "However, the Agency cautions readers of this report about relying on the results of our testing or other published test results to promote such systems as an effective means to address the backover crash risk."
The report then goes on to identify rain, fog, glare and driver limitations as possibly reducing the effectiveness of backup cameras. Even taking these limitations and the report's caveat into account, installing a backup camera is probably the safe thing to do.
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