CCTV Lens, Housing & IR
Camera Lens Mounts
C-Mount Lens
The flange back (distance from the surface where the lens comes in contact with the camera to the focal point) of C-Mount lens is 17.526mm (0.69 inch). This is the only difference between the C-Mount lens and CS-Mount lens. C-Mount lens, as well as CS- Mount, is 1 inch diameter with 32 TPI (threads per inch). A C-Ring (5mm spacer ring) is required when a C-Mount lens is to be mounted to a CS-Mount camera unless the camera has built-in Flange-back Adjusting Ring.
CS-Mount Lens
The flange back of CS-Mount lens is 12.5mm (0.492 inch). This is 5mm shorter than the C-Mount lens and you need a 5mm spacer ring (or, C-ring) when you mount a C-Mount lens to a CS-Mount camera. (So, CS-Mount camera is always compatible with C- or CS-Mount lens. But, C-Mount camera is not compatible with CS-Mount lens. Most professional cameras are CS-Mount cameras and include a C-ring.
Fixed Mount Lens
While C- or CS-Mount lens can be changed according to your application, the fixed mount lens, usually found on board cameras and mini cameras does not have standard mount size and can not be changed as easily as C- or CS-Mount lens.
Focal Length and Angle of View
Focal Length (FL) is the distance from the center of a lens to the focal point (CCD sensor chip). FL, as well as the CCD chip's format, is the major factor to determine the angle of view of a lens. For example, a 6.0mm FL lens on 1/3" sensor format has 56.8 degree of diagonal angle of view and a 5.0mm FL lens on 1/3" sensor format has 66.9 degree. But, the same 6.0mm FL lens can see 75.5 degree on 1/2" sensor format. The angle of view also varies a little depending on the manufacturer of the lens. For 1/3" CCD chip camera, the following formula is a simple way to determine the focal length of a lens needed.
(Distance to subject / Width of subject) x 4.5mm = Focal Length.
For example, if you want to watch a subject of 5.5ft width at 10ft distance with a 1/3" CCD camera, you will need an 8.0mm FL lens (10ft / 5.5ft x 4.5mm = 8.18mm). An 8.0mm FL lens mounted on 1/3" CCD camera will cover the subject you want to watch.
Optical Speed (f-number)
Optical Speed is about how fast a lens collects lights and is defined by the f-number like f/1.2, f/2.0, etc. This speed is determined by the Focal Length(FL) and the Diameter(D) of a lens; f- number =
FL/D.
Larger FL, if the Diameter is same, makes higher f-number (like f/4 or f/8) lens that collects less lights to the camera sensor and results a slower lens. Lower f-number (like f/1.2 or f/1.4) lenses pass more lights to the camera sensor. Larger Diameter, if the FL is given, will make a lower f- number lens which can operate in lower light level.
In conclusion, the lower the f-number, the more lights reaching the camera sensor and the better the video picture. The f-numbers are usually marked at the iris rings of lenses.
Camera Housings
The following are the dimensions of economically developed Outdoor Housing Cases for the CCTV Cameras;
Small size: 80(W) x 70(H) x 260(D) mm
Medium size: 103(W) x 98(H) x 370(D) mm
Large size: 142(W) x 115(H) x 392(D) mm
Professional Cameras should be mounted in medium or large size housing cases and Web Cameras in large size ones. A heater and/or blower can be built into medium or large size housing case. When a heater and/or blower is built-in, the available inside depth length is reduced by about 40 to 50mm. A heater and/or blower housing is usually required to be powered separately by 110VAC or 24VAC.
Other special housing cases such as dome camera housings, triangular ceiling or corner mount housings, elevator-cab housings, explosion-proof housings are usually expensive.
Illumination
To see properly, a video surveillance camera requires a certain amount of lights produced by natural or artificial illumination. B/W cameras work with any type of light sources, but color cameras need lights that contain all the colors in the visible spectrum.
The amount of lights is defined by LUX (Lumens per Square Meter). One LUX is a candle light volume at one meter distance. Followings are some examples of natural lights expressed in LUX.
Full daylight: 10,000 LUX Very dark day: 100 LUX Twilight: 10 LUX
Deep twilight: 1 LUX Full moon: 0.1 LUX Quarter moon: 0.01LUX
A good B/W camera can see in full moon condition. But, a color camera will need an additional artificial light in full moon.
C-Mount Lens
The flange back (distance from the surface where the lens comes in contact with the camera to the focal point) of C-Mount lens is 17.526mm (0.69 inch). This is the only difference between the C-Mount lens and CS-Mount lens. C-Mount lens, as well as CS- Mount, is 1 inch diameter with 32 TPI (threads per inch). A C-Ring (5mm spacer ring) is required when a C-Mount lens is to be mounted to a CS-Mount camera unless the camera has built-in Flange-back Adjusting Ring.
CS-Mount Lens
The flange back of CS-Mount lens is 12.5mm (0.492 inch). This is 5mm shorter than the C-Mount lens and you need a 5mm spacer ring (or, C-ring) when you mount a C-Mount lens to a CS-Mount camera. (So, CS-Mount camera is always compatible with C- or CS-Mount lens. But, C-Mount camera is not compatible with CS-Mount lens. Most professional cameras are CS-Mount cameras and include a C-ring.
Fixed Mount Lens
While C- or CS-Mount lens can be changed according to your application, the fixed mount lens, usually found on board cameras and mini cameras does not have standard mount size and can not be changed as easily as C- or CS-Mount lens.
Focal Length and Angle of View
Focal Length (FL) is the distance from the center of a lens to the focal point (CCD sensor chip). FL, as well as the CCD chip's format, is the major factor to determine the angle of view of a lens. For example, a 6.0mm FL lens on 1/3" sensor format has 56.8 degree of diagonal angle of view and a 5.0mm FL lens on 1/3" sensor format has 66.9 degree. But, the same 6.0mm FL lens can see 75.5 degree on 1/2" sensor format. The angle of view also varies a little depending on the manufacturer of the lens. For 1/3" CCD chip camera, the following formula is a simple way to determine the focal length of a lens needed.
(Distance to subject / Width of subject) x 4.5mm = Focal Length.
For example, if you want to watch a subject of 5.5ft width at 10ft distance with a 1/3" CCD camera, you will need an 8.0mm FL lens (10ft / 5.5ft x 4.5mm = 8.18mm). An 8.0mm FL lens mounted on 1/3" CCD camera will cover the subject you want to watch.
Optical Speed (f-number)
Optical Speed is about how fast a lens collects lights and is defined by the f-number like f/1.2, f/2.0, etc. This speed is determined by the Focal Length(FL) and the Diameter(D) of a lens; f- number =
FL/D.
Larger FL, if the Diameter is same, makes higher f-number (like f/4 or f/8) lens that collects less lights to the camera sensor and results a slower lens. Lower f-number (like f/1.2 or f/1.4) lenses pass more lights to the camera sensor. Larger Diameter, if the FL is given, will make a lower f- number lens which can operate in lower light level.
In conclusion, the lower the f-number, the more lights reaching the camera sensor and the better the video picture. The f-numbers are usually marked at the iris rings of lenses.
Camera Housings
The following are the dimensions of economically developed Outdoor Housing Cases for the CCTV Cameras;
Small size: 80(W) x 70(H) x 260(D) mm
Medium size: 103(W) x 98(H) x 370(D) mm
Large size: 142(W) x 115(H) x 392(D) mm
Professional Cameras should be mounted in medium or large size housing cases and Web Cameras in large size ones. A heater and/or blower can be built into medium or large size housing case. When a heater and/or blower is built-in, the available inside depth length is reduced by about 40 to 50mm. A heater and/or blower housing is usually required to be powered separately by 110VAC or 24VAC.
Other special housing cases such as dome camera housings, triangular ceiling or corner mount housings, elevator-cab housings, explosion-proof housings are usually expensive.
Illumination
To see properly, a video surveillance camera requires a certain amount of lights produced by natural or artificial illumination. B/W cameras work with any type of light sources, but color cameras need lights that contain all the colors in the visible spectrum.
The amount of lights is defined by LUX (Lumens per Square Meter). One LUX is a candle light volume at one meter distance. Followings are some examples of natural lights expressed in LUX.
Full daylight: 10,000 LUX Very dark day: 100 LUX Twilight: 10 LUX
Deep twilight: 1 LUX Full moon: 0.1 LUX Quarter moon: 0.01LUX
A good B/W camera can see in full moon condition. But, a color camera will need an additional artificial light in full moon.