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Camera

Cameras classified by their technology Two technologies to transmit the video signal:

  • Analog cameras:
    • The video signal is transmitted over a coaxial cable to a recorder that converts the analog signal into digital data.
  • IP cameras :
    • The video signal is captured by the same type of sensor as the analog camera, but it is digitalized directly in the camera by an embedded processor. Data are then transmitted to a recorder, over a network cable(Cat 5 or 6).

Cameras classified by their form

Conventional cameras

  • A little square box with removable lens. These cameras offer more flexibility in the choice of lens with special features: Dynamic lighting (WDR, wide dynamic range), wide or long range (lens 50, 100 or 200mm, to see very far).
  • They are used when a specific environment requires a special casing.

Dome Cameras

  • These cameras have a more discreet field of view, the bubble that covers the camera makes it more difficult to change its target by mistake, unlike conventional cameras and “bullet” that will change alignment if hit.

Bullet cameras

  • These cameras have an integrated lens, they offer little flexibility, and can be moved if hit. Their advantage is their price.

Specialized cameras

  • Some cameras have a special form because the manufacturer has decided it others are designed specifically to be used as hidden cameras. Given their size and shape, they can be integrated into common elements of the environment to be monitored.

Cameras classified by their ability to perform under different environments

 

Indoor vs outdoor cameras

All outdoor cameras may be used indoor as well without problem, however, an outdoor camera must withstand:

  • Low temperatures;
    • Many cameras available in Canada show a nominal range of operation temperature starting at -10 degrees Celsius, they can usually survive the winter if they are somewhat protected from the weather and located in areas further south, such as Montreal or Toronto.
    • In order to get a camera that is certified to operate at -50 degrees, ones must anticipate a much higher price
  • High humidity and sometimes rain directly;
    • Higher quality cameras bear a notice about their weather resistance, it is expressed as follows: IP 65, IP 66, IP 67. The higher the number, the more the camera can withstand moisture and dust.
  • Typically, outdoor cameras must also be resistant to shocks; therefore dome cameras with vandal-resistant casing are most appropriate.
    • Dome cameras offer very good range of outdoor models.
    • Conventional cameras must be placed in a protective casing, waterproof, ventilated for summer and heated for the winter.
  • Other specialty cameras:
    • There are many types of protective enclosures such as: explosion proof, waterproof, dustproof, and others.

Features of cameras with regards to lighting:

  • Darkness is the enemy of cameras;
    • for this reason, cameras with built-in infrared lights are very popular, however they often give a disappointing result because under infrared light, the image becomes black and white and the subject becomes dazzled, making details difficult to grasp.

The following pictures show, on the left, an image captured by a camera with infrared lighting; on the right, by a camera featuring a good “Day / Night” function (True Day / Night)

Here are images captured by the same cameras during daytime.

  • Too much light is just as bad,
    • Light must be shooting from behind the camera towards the scene in order to obtain good results.
    • If lighting comes from behind the subject towards the camera, captured subject becomes dark (Just as taking a picture when facing the sun), the effect is even worse if the subject is moving.

To overcome this situation, there are cameras with all kinds of features from Auto-Iris to WDR (Wide Dynamic Range). While many manufacturers sell their products as being WDR, there are large differences in the results obtained by each. Rely on our expertise.

Choice of lenses

No single camera can meet all needs; again, our experience is very much valuable to choose the appropriate one.

The opening (coverage area) of a lens is expressed in millimeters, there is a large range of choice such as 4mm lens or 9mm as well as varifocal (manually adjustable). The higher the number, the farther we can see. To express this notion in a very simplistic way, assume that we can recognize someone, see his face with a 4mm lens, if the subject is at about 4 feet; with a 15 mm lens we will see the same face at 15 feet and therefore with a lens 50 mm, we will see a face at 50 feet.

On the other hand, the width of the captured scene will be proportionately narrower with a 50mm lens than with a 4mm lens. We always have the choice between seeing a “large scene” or seeing “more details”. The concept of “details” in the image is also influenced by the resolution of the sensor; here come into play, the IP “megapixel” cameras, they offer higher resolution, more pixels in the image, it is then possible to get more details. On the other hand, higher resolution (mega pixels), requires a more appropriate lighting.



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