By Roger Kittelson, F88803, Whitney, Texas
I hope this guide helps you with your purchase of a quality rearview camera system. Please note that I’ve tried to provide accurate information in simple, non-technical, layman’s terms. While many others may try to baffle you with their… you know what… I want you to understand exactly what to look for in a rearview camera system, so you’ll have the best system available, and avoid making the mistake of purchasing something that can be dangerous.
Automatic System Switching
Possibly the most important feature to look for when purchasing a rearview camera system is that the system’s ability to switch on automatically whenever the vehicle’s transmission is placed in reverse. This is accomplished by connecting a single wire to the vehicle’s backup light circuit, sending a signal to the rearview camera system, causing it to switch on without any action by the operator.
Many so-called ‘rearview camera systems’ don’t have this feature, and will require you to manually switch the system on every time you want to see behind you. The higher-end systems (any true ‘rearview camera system’) will have this ability to switch on automatically, in addition to being turned on manually any time using the monitor’s front panel power button (or wireless remote control, if so equipped).
Since it’s very inconvenient and extremely unsafe for the motor vehicle operator to be required to switch the system on manually every time he or she wants to back up, it’s imperative that you never purchase a rearview camera system without the ability to switch on automatically. If the system you’re considering doesn’t clearly list this feature, it almost certainly doesn’t have this feature. Never purchase a rearview camera system without this feature.
Mirror Image Capability
A rearview camera system should have the capability to produce a ‘mirror’ (or ‘reverse’) image through the camera and/or monitor. Many of the systems sold (especially those on eBay) don’t have this capability. It doesn’t matter whether the camera produces a ‘mirror’ image, or the monitor reverses the image left to right, or as on some high-end systems, both the camera and monitor can switch between ‘normal’ and ‘mirror’ images.
Why do you want a ‘mirror’ image? In order to see the same type of image that you would see in a rearview mirror, the camera and/or monitor must be capable of reversing the image produced. This capability will provide the same type of image through a rearview camera system that you would see if you were looking into a rearview mirror, and that’s exactly what you want for safe operation. Many high-end systems not only allow you to select between a ‘normal’ and ‘mirror’ image but also permit you to ‘flip’ the picture vertically for additional camera mounting options.
If a system doesn’t specifically list this feature, then it almost certainly doesn’t have this feature. Never even consider purchasing a rearview camera system that doesn’t have this feature.
Wide Angle Field of View
The field of view provided by any camera is determined by a combination of the image sensor (see “CCD vs. CMOS Image Sensor” below) size and lens focal length. The larger the image sensor, the wider the possible field of view. However, a larger image sensor does not necessarily guarantee a wider field of view. Many rearview camera systems utilize a 1/4″ image sensor and provide only a 60 to the 90-degree field of view. While a 90-degree field of view may be sufficient for some smaller vehicles, a 110 to a 120-degree field of view is preferred. You should absolutely avoid any system that produces lower than a 90-degree field of view. Most high-quality rearview cameras that utilize a 1/3″ image sensor produce a 110 to a 120-degree field of view — that is ideal for most applications.
On the other hand, there are some rearview systems advertised with 150, 160, 180 or even 210-degree fields of view. This super-wide field of view cameras are not intended for use on rearview camera systems, and will generally produce a ‘fish-eye’ image that will be extremely distorted and very dangerous to use as part of a rearview camera system. A few very rare specialized rearview cameras are designed with 150 or 160-degree fields of view, but these are special units and are very expensive (not generally available for everyday use).
I can’t emphasize strongly enough that you should never use a camera that provides a ‘fish-eye’ view — you will eventually back into or over something or someone!
CCD vs. CMOS Image Sensor
The two types of image sensors that are available for rearview (backup) camera systems are the CCD (“charge-coupled device”) and CMOS (“complementary metal-oxide-semiconductor”). The type of image sensor that your rearview camera system uses will be the most important factor in determining picture quality. Besides the overall resolution, a camera that utilizes a CCD image sensor will provide significantly better images under very low and very bright lighting conditions.
All except the lowest quality consumer digital photographic and video products utilize CCD image sensors. All professional digital photographic and video equipment utilize CCD image sensors. Although there are some reasonably high-quality CMOS image sensors, no CMOS image sensor will deliver the quality image that a CCD image sensor will provide. Much lower-priced (and some more expensive) systems use the less expensive and inferior CMOS image sensor.
Given the option, you should always select a rearview camera system that utilizes a high-quality CCD image sensor from a well-known manufacturer. Sharp and Sony CCD image sensors are the best available. If the system you’re considering purchasing doesn’t state that it utilizes a “CCD” image sensor, then it almost certainly doesn’t.
Weatherproof Camera, Cables & Connectors
Remember, a camera mounted on the exterior of a motor vehicle will be subjected to more than just water. Such a camera may be exposed to a wide variety of elements, including water, snow, ice, salt, road grime, oil, dust, detergents, and high-pressure washes. Just as the camera can be exposed to these elements, so are the exterior cables and connectors.
Weatherproof cables and connectors should also be used for all exterior installations. Many systems sold (particularly on eBay) utilize RCA type connectors for exterior connections. Stay away from these systems, as RCA connectors (the same type of connectors found on most televisions and VCRs) are not weatherproof — they should never be used for exterior connections.
Exterior connections should always be made by weatherproof connectors — weatherproof connectors screw together, so they can’t accidentally come unplugged. This is especially useful when using a rearview camera system with a trailer and tow vehicle combination.
Many systems include interior RCA connections. These interior connections are not subject to any of the elements found on the exterior of a motor vehicle and are perfectly acceptable. In fact, these interior RCA connections can be useful for adding additional cameras (even those from another manufacturer), or for connecting other video and/or audio devices.
Never purchase a rearview camera system that utilizes RCA type connectors for exterior connections. These connectors are not designed for exposure to the elements, and they will eventually fail. Beware of sellers who claim that their inferior RCA connectors designed strictly for interior use are superior to screw together waterproof connectors. Think about this and decide for yourself.
Infrared Night Vision
This is probably one of the least understood features available, and yet, it is one of the most important features. Although a high-quality camera (especially a high-quality CCD camera) can provide a picture under a wide variety of lighting conditions (including very low light), it can’t provide a clear picture in near or total darkness. That’s where the infrared night vision illumination LED’s (light-emitting diodes) come in.
On a high-quality night vision equipped camera, the infrared LEDs turn on automatically whenever the ambient (background) light drops to a level that’s too low for the image sensor to produce a high-quality picture. The infrared LED’s operate at a light frequency that is well above the human eye’s ability to see, but the image sensor in the camera is designed to detect this light just like the visible light that we can see.
The primary difference between visible and infrared light is seen when using a color rearview camera system. On a monochrome (often referred to as “black and white”) rearview camera system, there is little difference seen in the image. However, since infrared light doesn’t produce colors that are visible to the human eye, all color systems will produce a monochromatic image at night.
One big difference between a high-quality rearview camera and a lower quality one is its ability to illuminate the area seen by the camera. Ideally, the infrared illuminators will illuminate the entire field of view produced by the camera and will illuminate out to a distance of at least 20 feet from the camera. The higher-end systems will typically illuminate out to a distance of 30 to 50 feet from the camera.
While the number of infrared LED’s may or may not be important (just as with light bulbs, various infrared LED’s have higher or lower light intensities), the total light output and the camera’s sensitivity to infrared light, will determine the overall performance of the camera’s night vision capabilities. Some sellers will make ridiculously exaggerated night vision claims (no onboard infrared illuminators will extend beyond approximately 50 feet), and these claims should be ignored as nothing more than sales hype.
Never consider purchasing a rearview camera system that does not include infrared night vision illumination. The infrared night vision illuminators should provide a minimum of 10 feet of illumination, and 20 to 30 feet or more of illumination is strongly recommended.
Automotive Power Source
One of the most serious questions for most users of these systems, isn’t whether or not the system they purchase will work with their vehicle — it’s how well and how long will it work with their vehicle? Many of the lower quality systems (including many sold on eBay) do not include any type of voltage regulator or filtering circuit. The lack of such a circuit will cause the constant varying voltage produced by the vehicle’s electrical system to either damage the system, or at a minimum, produce serious variations in picture quality.
If the system you’re considering doesn’t specifically state that it has a voltage regulator or filter, then it probably doesn’t.
Nearly all rearview camera systems will work on any vehicle that operates from 12 volts DC — that’s nearly every late model car, pickup truck, sport utility vehicle, recreational vehicle, and trailer. However, there are exceptions to this rule, including some specialty vehicles, as well as many commercial and military vehicles. Some rearview camera systems are capable of operating at a variety of voltages, usually either 12 to 24 volts DC, or 12 to 32 volts DC.
Some rearview camera systems include optional voltage regulators that can be added for use on those vehicles that operate from the higher voltages (usually 24 or 32 volts DC). This option is necessary if you plan to install the system on a vehicle that operates from one of these higher operating voltages.
Audio Monitoring
Audio capability can be helpful when the driver needs the assistance of a helper while backing. While you may or may not require audio, it can also be useful when a camera is being used to monitor the interior of a trailer (carrying people or animals). While some systems include audio, others do not. If the description does not specifically state that audio is included, chances are it’s not.
The only disadvantage to audio is that in order for the microphone within the camera to receive sound from outside the camera housing, there needs to be a small hole leading to the outside world. While the higher quality cameras with audio are designed to keep water out during normal use, there is a possibility that high pressure spray from a car wash (or other source) could possibly enter the camera housing.
Most of the higher quality rearview cameras that have audio house the microphone within a sealed compartment that is separate from that which houses the camera and/or locate the microphone hole on the backside of the camera (the side that faces toward the vehicle), to prevent water from being forced into the microphone hole.
Types of Monitors
Although there are several sizes, a wide variety of quality, and many different features, there are essentially two different types of monitors available — these are CRT (cathode ray tube — commonly referred to as a “picture tube”) and LCD (liquid crystal display) monitors. Most (if not all) color rearview camera systems will use an LCD type monitor. Most (if not all) monochrome (black and white) rearview camera systems will use a CRT type monitor.
The LCD monitors are most commonly available in 5″ to 5.7″ (measured diagonally) and 7″ to 7.2″ (measured diagonally) screen sizes. These are sometimes referred to by their generic screen sizes, like just 5 or 7 inches, leaving off the decimal point. Of the available LCD type monitors, the TFT-LCD (thin-film transistor – liquid crystal display) is significantly better than the LCD type. If the seller does not clearly specify that the monitor is the TFT-LCD type, chances are it’s not.
When selecting a rearview system that uses an LCD type monitor, always choose the TFT-LCD type monitor for the best picture under the wide variety of lighting conditions encountered while operating a motor vehicle.
The CRT type monitors found with most monochrome rearview camera systems come in two basic types — ‘gray screen’ (resembles an old ‘black and white’ television screen) or ‘green screen’ (the monitor actually produces a picture with a green hue). Neither of these has any overwhelming advantages or disadvantages, although some people do have a preference. The idea behind the ‘green screen’ monitor is that the color green is easier on the eyes in the darkness, and as with military night vision equipment, produces an image that makes it easier to discern variations in shades of color, especially at night.
The LCD type monitors are significantly smaller and lighter than the CRT type monitors, making it easier to mount them in smaller vehicles. The larger CRT type monitors must usually be mounted on top of the dashboard, the transmission hump, hung from overhead, or occasionally mounted into the dashboard. The smaller LCD type monitors can be mounted in any of these locations, as well as on the face of the dashboard, on the sun visor, hung in place of the rearview mirror, or many other locations (depending upon the specific vehicle).
In most cases, you should avoid those rearview systems that use a monitor with less 5″ diagonal measurement, as they do not provide adequate detail for safe backing of larger vehicles. Any system that has a monitor with less than a 5″ diagonal measurement should only be considered for use as a rearview or backup camera system on a car or other smaller passenger vehicle, and NEVER on a larger type vehicle.
Types of Cameras
There are two common types of cameras used for rearview camera systems. These are the ‘surface’ (or ‘standard’) mount and the ‘flush’ (or ‘keyhole’) type cameras. Each type of camera has its own specific advantages and disadvantages, and each is designed for a specific type of use.
Most larger vehicles are best suited to the surface mount camera, which can be attached to any flat (or near flat) surface (and most other surfaces utilizing a variety of mounting options and brackets). These cameras are the type most often observed mounted high on the rear of a vehicle, aimed down at approximately 45 degrees. This mounting position provides a commanding view of the area behind the vehicle, and because of the downward angle, provides excellent depth perception. This type of camera is by far the best choice for larger vehicles, including recreational vehicles, trailers, busses, and all commercial vehicles.
On many passenger vehicles, pick-up trucks, and sport utility vehicles, the ‘flush’ (or ‘keyhole’) type camera is the preferred choice. This type of camera mounts through a hole in the body of the vehicle and provides a view that is more or less directly level with the road surface (the better ‘flush’ mount cameras include rings that permit slight angling of the camera). While this type of camera does not provide the degree of depth perception provided by the ‘surface’ mount camera (because it can’t be angled down to the same degree), it is well suited to passenger vehicles and provides a much cleaner and unobtrusive installation, since the only part of the camera that is visible is the lens cover and bezel.
Both types of cameras are available with infrared night vision capabilities, although availability varies from one system to another. In most cases, the night vision capability of ‘flush’ mount cameras will provide less illumination distance than an equal quality ‘surface’ mount camera (this is due to the limited number of infrared LED’s that can be positioned within the ‘flush’ mount camera housing). While audio is available on many of the ‘surface’ mount cameras, I’m not aware of any ‘flush’ mount cameras that include audio.
Wired vs. Wireless
While the picture produced by a high-quality wireless system may be okay when the vehicle is stationary, every wireless device (everyone!) is susceptible to interference, and that interference will be worse when the vehicle is in motion. Because a wireless system transmits a video image through the air, instead of via a cable, there can be some interference from a variety of sources, including electrical interference, high power radio and television transmitters, and many other sources encountered as the vehicle moves.
Think of the difference in quality between the images produced by an old television antenna on the roof, versus a modern cable television signal. The mere fact that the video image must be converted to a radio signal, transmitted through the air, and converted from a radio signal back to a video image at the receiver and monitor, means that the possibility for signal degradation is a serious consideration.
One serious consideration should be that most of the wireless systems sold (on eBay and elsewhere) are total and complete garbage. Most don’t provide the ‘mirror’ image (see “Mirror Image Capability” above). Most are not weatherproof. Most have directional antennas on the camera and receiver that must be aimed directly at each other. Most have antennas that are easily broken during normal use.
I personally prefer a wired system. If you absolutely insist upon a wireless rearview system, then you will have to settle for a lower quality picture than you would have with a high-quality wired system. Check the specifications of any wireless system you are considering purchasing very carefully – then buy a wired system instead!