The FAQ For CCTV Lens

Q1: How do I set up an Auto Iris lens?
 A : An Auto Iris lens has two ‘pots’ on the side commonly marked ALC (Automatic level control) and LEVEL.
 The ALC control has settings of PEAK and AVERAGE (P+A).
 The LEVEL control has HIGH and LOW settings ‘H+L’.

 ALC
 The adjustment allows control over any bright areas in the scene e.g. sun reflection through windows, street lighting etc. There are two settings PEAK and AVERAGE.

 If set to PEAK, bright areas in the scene are taken into account more, reducing the contrast in the surrounding area. This allows more detail to be seen in the bright areas.

 If set to AVERAGE the lens takes the bright areas less into account which usually causes over brightness or flare in these areas, but raising the contrast of the surrounding area.

 LEVEL
 The only correct way to set the VIDEO LEVEL is by the use of an oscilloscope, for most Engineers this is not an option.

 A more practical method is to use a service test monitor and a camera that you know has been set up correctly to 1 volt peak to peak.

 Put the video output from this tested camera into the test monitor and adjust the contrast and brightness until you are satisfied with the picture. Mark the contrast and brightness controls so that you can set them to this position again.

 Set up each camera adjusting the ALC (as above) then adjusting the LEVEL to obtain a picture similar to that achieved with the test camera. (Making sure that your test monitor is set to your marked positions)

 NB: On most zoom lenses the ALC adjustment is a speed control for the Iris motor and is best left in the mid position. The Amplifiers on Auto Iris lenses are sensitive; so adjust the LEVEL and ALC with a proper trimming tool instead of an ordinary screwdriver, which can induce small voltages.

Q2: Manual or Auto Iris Lens?
 A : The iris is the part of the lens that determines how much light falls upon the camera CCD sensor.The Manual Iris 'MI' lens has this fixed at the time of installation. As the light levels change in the scene, the lens can do nothing to prevent either too little or too much light entering the camera. Virtually all cameras employ an Automatic Electronic Shutter 'AES' to compensate for these variations when fitted with an MI lens. However they are only able to cope with a relatively small change in light levels.An MI lens should never be used in an external situation, as the camera will be unable to cope with large changes in light levels. Use an Auto Iris ‘AI’ lens in this case, or indeed anywhere where large scene illumination changes take place.
 The advent of new sensor technology such as PIXIM may result in a change to this situation in the future.

Q3: Lens focal length "mm the number of" buy DIY !
 Step1.Measure the distance between "camera set up point" and "the target point", the distance = (A) m
 Step2.Measure the width of "target points" need to surveillance, the width = (B) m
 Step3. In accordance with the "Step 1" measured results "value A" s in the following table, find the closest to the needs of their surveillance photos
 (That is, the sample photos of " Width of picture you catch" and "the clearance of characters" similar to their own environmental monitoring)
 Step4. On the photo should be used in which mm lens focal length number => that have the lens focal length you need!
Step5. Frequently to adjust:
(Q1):the control according to the following example, to find a degree and I can see Wide similar location, but the characters are feeling too small, how do?
 (Q2):control sample photos, find a character size and clarity, and I need almost the same, but the example of the lens can be used according to wide shot but not enough degree, how to do?
Note 1: monitoring cameras can seet 3:4 ratio of screen length, the above example is only marked Wide degree photos, photo length (height) = width X0.75
(Example: from the Department to use 60mm 5M length of the camera results 0.5M, the picture height 0.5x0.75 = 0.375M)
 Note 2: These values form the rack to monitor the photo is about 1.2M in height from the ground office, head-shot from in front of people and cars.If the photo shadow in the general height of the ceiling rack, ceiling or high ceiling environments, photographed on the first floor or second floor, third floor, shoot the first floor overlooking the shooting at this time ... ...
 Larger angle, you can take a larger area, but the figure would be less.
 Note 3: The above values for the use of the form 1/3 inch CCD cameras for surveillance testing, if the same applied to the lens focal length 1/4 inch CCD
 Surveillance cameras, camera angles will be smaller (smaller angles, shooting range will be available with smaller, but people will feel slightly larger than aMore).

 1/3 CCD and 1/4 CCD more surveillance cameras angles are as follows:

Q4: What is the Difference Between C & CS Mount lenses?
 A : The physical difference is that the back of a CS mount lens is 5mm closer to the chip than a C mount lens. You can always use a C mount lens on a CS mount camera by using a 5mm spacer ring (many cameras now have C/CS selectable adjustment screws or rings). You can never use a CS mount lens on an older style C mount camera. Cost wise the CS mount lens is much less expensive since it uses fewer glass elements. Quality of image is the same. C mounts are becoming less and less popular and are generally only used on the more telephoto focal lengths such as 25, 50 and 75mm, and bigger zooms.

Q5: What is the vari-focal lens or zoom lens?
 A : A Vari-focal is a lens that is designed to meet the most challenging jobs by giving the installer the flexibility to adjust between different focal lengths using only one lens. When the situation calls for an odd focal length lens or you are not sure of the correct focal length required for the installation, using a Vari-focal lens is the perfect choice. How many times have you or your installer set-up a job just to be called back because the customer was not satisfied with the field of view of the picture? More than once, most likely. A simple adjustment to the zoom and focus on a Vari-focal lens is all that is needed to rectify the situation on the spot: a less costly and time-consuming prospect than having to order and install a different monofocal lens altogether.Surveillance effects are maximized since any desired angle of view can be obtained.