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Buying advice for cameras

Buying advice for cameras




 Advice on buying cameras

(This guide is work in progress!!!) 

The quality of a camera depends on a number of factors. Generally almost all cameras are produced in China using mainly American or Japanese components. The key component is the sensor which is made using one of two different technologies. The first and cheapest is the CMOS sensor which is usually fitted to budget cameras. They tend to pick up UV light when the sun is strong in summer which can tint the image red or orange. It is very sensitive to the sun when it is facing that direction. The night image is generally poor with just enough detail to give a usable image. It has two big advantages price and size. The low price and the small size these cameras can be made make them popular in situations where they are only needed for reversing. A more recent development is the OV7950 (NTSC) or OV7949 (PAL) sensor which although it is CMOS technology they are often called CMD sensors. They handle the sun a little better and give a higher resolution image with much improved colour definition. They will give a useable night view as you will see within some of my listings. On some monitors the interaction between the image processors within the camera and monitor can cause colours to be faint. They are also weaker at handling areas of shade withiin areas brightly lit by the sun. Even so they are a considerable improvement on previous CMOS sensors. More recently a new sensor from Micron is giving very good colour in the day with a reasonable night view. The second technology is CCD. These produce good colour definition and very good night vision if you have cameras fitted with the Sharp or Sony sensors. Cheaper CCD sensors are generally Chinese made and their night view is disappointing. The CCD sensor are roughly double the price of CMOS and require more electronics. This makes the size of the cameras larger. They make good cameras where night vision is important or you want an always on option. They suffer much less from glare from the sun. There are a growing number of very small CCD cameras coming on the market and we now stock some of these models. The picture quality does tend to suffer slightly compared to the larger CCD cameras. Their small size though give many advantages in mounting on cars.

Wiring arrangements

When a camera is needed for reversing only it is normal to wire the postive lead of the camera to the positive wire of the reversing light. This is usually done at the rear light cluster where it is easier to access and identify the wires. Some modern cars now have reduced voltages to the rear lights or use a system where a microprocessor controls their operation from a data and power feed. This makes installation more difficult and a specialist auto-electrician should be considered. It usually involves the use of a relay or special interface unit otherwise it can seriously upset the vehicle electronics. The second form of wiring is where the power is always on. This is achieved by attaching the positive wire of the camera to a power source that comes on with the ignition. We recommend in both cases the use of a low amperage fuse as near to where you connect to the positive power supply as possible. CAB101 is suitable for use in dry areas. The connection of the negative wire should be to a good earthing point (ground/vehicle body). You frequently find a grounding point near the rear light cluster. Cameras should never be connected directly to the vehicle battery. Many of our camera systems can be set up to run off a single power source at the front of the vehicle (or lighter plug). The cameras are not harmed by being left on all the time the ignition is on. The camera sensors were generally developed for applications like lane departure systems which are naturally always on.

Styles of camera

Bracket_0020_camera_0020_nice_0020_angled_0020_view.jpgThe bracket camera is a very popular model. It is usually placed up high looking down to give a view across the complete rear of the vehicle. It is also frequently used looking up more and left on permanently to give a constant rear view. The sun shade means they produce a good picture on most days and situations. With 18 infra-red LEDs the night view is usually good. The main disadvantage of the model is their size and the fact they are quite conspicuous. They are mainly used on lorries, caravans, high top vans and motorhomes. We have had them used on barges, combined harvesters, JCBs, potato pickers, horseboxes (on the inside and out), a carnival float and Father Christmas's sledge!

CAM02520just20camera.jpgThe bullet camera is a favourite of the car owner. They can be mounted in the bumper or within the boot lid. They have the advantage of being almost flush so are much less easily damaged. If they can be mounted in an area of shade then sun is not usually a problem, but if they are not then glare from what sun we have can be an issue. The CCD cameras are much less affected. They make a good reversing camera, but are not as good for an always on rear view. Being lower down they need the glass front cleaning regularily to keep a clear image.

 

CAM071W_reversing_camera_side_view_plus_pound_coin.jpgCAM042_0020_NTSC.jpgThe number plate camera has several variations. These are all designed to fit within the number plate area often using the flat area above a number plate recess as the mounting surface. Some have brass hollow studs which take the place of one of the number plate fixing screws. The wires go through the middle of the stud. They are almost always CMOS to keep their size down. Although designed for the number plate area they can be mounted in a variety of places both inside and outside the vehicle. There are models based on a frame for the number plate or ones that fit just above the number plate.

CAM070BS_side_view.jpg

The dome style camera we stock is very useful when you suspect the camera might have to cope with low branches. They fasten securely to the vehicle and are robustly built. Our current stocks have sound. Normally fitting a microphone introduces a weak point where water may force its way in. On the Dome camera the microphone is protected by the outer shell and our experience is they are rarely suffer from leaks.

 

 

Types of connection

The cameras we sell either have a yellow RCA (phono) socket and 2.1/5.5mm power plug or a 4 pin screw type connector which is fully waterproof. The RCA type is low cost and if kept dry will be trouble free. The 4 pin connector is both locking and waterproof which makes them very reliable. With the RCA connector if you cannot get it in the dry of the interior of the vehicle then you need to seal with amalgamating tape and then a layer of insulating tape. The 4 pin connector is a great one to use on vehicles like motorhomes. Many people do not like the idea of putting holes in their coachwork so opt for a bullet camera in the skirt of the home. You can then run the cable to the front of the vehicle almong the underside of the vehicle. They also tend to be used on commercial vehicles for the increased reliability. There are other forms of connector:- DIN, mini DIN, PS/2. As no standard has ever been produced the camera from one manufacturer may not fit that of another even if the plugs are the same.

4_pin_camera_pin_outs_2.jpg

This diagram shows a S-video style connector and one possible way it may be wired. We must stress that different manufacturers may use different pin outs. The key one is the 12v power as if that is wrong you destroy the camera. You can buy S-video to RCA converters in some shops. The problem with most of these is they will not work! S-video is not the same signal as composite. To convert one to the other means there are circuts within the adaptor to change the signal. The reversing camera will output a composite signal and the S-video plug is just the plug the factory had available. The adaptor will expect a S-video signal and will block the composite signal. The most usual way around this is to make your own adaptor.

PS2_style_plug.jpg

 

 Another very common connector is based on the same PS/2 style plug as on a computer mouse. One complication of these is the long cable that runns from front to back of the vehicle may only have 4 or 5 of the terminals connected. The diagram shows one possible way that the camera may be wired. Again this may vary from camera to camera. On some cameras they only have 5 pins which are now almost impossible to source. There are other variations of design of plug where the plastic locator will be of a different shape or position. The only time we would recommend a wireless system is to use the existing fitted cable runnning the length of a motorhome. The camera could be powered using the existing cable.

 

plug_and_pins.jpg The most common connector on systems these days is the four pin waterproof connector shown in the photograph. Again you cannot guarantee the pin outs will match on systems from different manufacturers so you need to check the position of the 12v positive. These offer the advantage of being locking and waterproof. The cameras are easily available and will be in years to come as more manufacturers change to them.

Viewing angle

Many people want as wide a viewing angle as possible. Many manufacturers know this and exagerate their statistics! There are 3 ways of measuring viewing angle:- horizontal, vertical and diagonal. The viewing angle a camera produces may not be the same as displayed on the monitor as edges are missed off to fit the geometry of the screen. As the viewing angle increases then lines that are straight begin to distort and curve. Once you go past 120 degrees this distortion because so bad that they descibe the lens as a "fish eye lens". Also distance becomes more difficult to judge which if you are using the camera as a rear view mirror is something you need to beware of. You can work out the viewing angle from the focal length of the camera lens together with the sensor size. The images below show the views produced by three different reversing cameras with an increasing camera angle. The vehicle behind was 4 parking bays back. The 60 degree camera gives a fairly good judge of distance, but the larger angles make it look much further away.

 

Views from different camera angles

 

Camera problems

The main thing that can go wrong with a camera is when fitting you get the +ve and -ve leads mixed up. Reversed polarity = smoke and a dead camera. After that the biggest enemy is water. Although the cameras are fully waterproof we advise they are not pressure washed. If you think the camera is in an area where high pressure jets may hit it then try to protect it in some way. Cameras being electronic, subject to vibration and rapid temperature changes are in quite a hostile environment. They can fail for this reason. With our cameras the 12 month guarantee means we replace any camera that fails (except the ones you melt fitting!) with a new one. Fortunatley we do not have to do this very often.

To look after your camera we recommend you avoid pressure washing them. If helps the night image if you avoid getting wax on the front glass of cameras fitted with IR LEDs. Corrosion can be a problem on some cameras. The bullet style cameras tend to be extruded alluminium which in our experience cope very well with the winter salt. Mine has been fitted 4 years with no corrosion. The bracket style camera had greatly improved in its resistance to corrosion. Our manufacturers have changed onto a shell with a high aluminium content. They cost a little more, but we see little evidence of corrosion on any returns we get.  It helps to wipe them clean and wax the outer body. If the paint does get damaged, then in winter when there is salt on the road they will corrode. Repairing the damage quickly will greatly extend the life of the camera. The cheap heavy cameras with a high zinc content will begin to corrode the first time it rains. If you wish to confirm this there are plenty of Chinese sellers who have them on ebay!