The following should aid you in preventing common installation problems and help you determine if a lens is actually defective.

LENS TYPES

Auto-iris
There are two types to auto-iris lenses currently available. "Video" type lenses contain an internal amplifier to compare the incoming video signal from the camera to adjust the iris to a level set by the user. "DC" type lenses contain no amplifier and are controlled by a circuit located within the camera to adjust the iris.

C-mount/CS-mount
CCTV lenses are available in two different lens mounts. "C-mount" lenses have a flange back distance of 17.526mm vs. 12.5mm for "CS-mount" lenses. Many of today's cameras can accept either type of lens, but it is important to make sure that camera and lens are compatible and set up properly. C-mount lenses can be used on CS-mount cameras by utilizing a 5mm adapter or adjusting the camera for C-mount lenses. Because of the shorter back focal distance, CS-mount lenses can only be used on CS-mount cameras. Your picture will be out of focus if you use a CS-mount lens on a C-mount camera.

Zoom lenses
Zoom lenses generally have motorized zoom/focus/iris functions or motorized zoom/focus with built-in auto-iris. All motorized functions are controlled by the lens controller. Many zoom lenses are available with pre-position potentiometers. Pre-position lenses utilize a variable-resistor (potentiometer) to indicate the zoom/focus position to the lens controller. This allows the operator to view different pre-set areas without having to re-adjust the zoom/focus each time.

AUTO-IRIS PROBLEMS - Video Type Lenses

The majority of lens problems experienced are auto-iris related. It is rare for a lens to be "dead out of box" and non-operation can be attributed to user error. If the auto- iris does not work try the following:

Is the camera configured for Video type lenses?
Current cameras normally accept both Video and DC type lenses using the same connector or a combination of terminal strip (Video type) and connector (DC-type).  For cameras with a single connector, verify the lens selection switch is in the 'Video' position.  For terminal strip cameras, verify the wires are installed properly for Power (+), Ground, and Video.

Is the auto-iris connector wired properly?
Verify that the lens connector is wired the same as it appears in the camera instructions. Correct connector wiring is crucial and incorrect wiring could damage the camera and lens. Reversal of the power and ground wires will usually blow a fuse or damage the circuit inside the camera and lens, so be careful.

Installing a connector

1.	Strip wire and twist gently to avoid frayed ends.
2.	Tin wire with solder and cut length to fit the pin of the connector.
3.	Pre-solder pin of connector. This will make installation of the wire easier.
4.	Install shrinkable tubing on wire.
5.	While heating pre-soldered pin, insert wire and remove solder iron. Hold wire until solder cools.
6.	Slide shrinkable tubing over pin and heat shrink.

Is the lens getting the proper voltage?
Using a voltmeter, measure the voltage across the power and ground outputs of the camera iris connector. Most lenses require at least 8.5 volts DC with a maximum around 15-16 volts. No voltage could indicate a camera problem.

Has the lens been adjusted properly?
Level
Main iris control. Adjustment towards high will open the iris, towards low will close the iris. After initial set-up of the iris to the desired video level, the iris will maintain this level in a variety of lighting conditions. Set-up should be performed in daylight as night-time set-up will commonly cause the iris to remain too far open during the day.

ALC
Iris sensitivity adjustment. Sets the iris reaction time fast or slow for changing light levels. Adjustment towards peak will increase sensitivity and reaction time, towards average will decrease both. Set to mid-range for most applications. You will not see a major change in the picture when adjusting the ALC.

Gain
Some lenses are equipped with a gain adjustment to reduce iris oscillation (iris opens and closes rapidly in bright light) with certain cameras. If oscillation occurs, adjust until the iris settles down.

RECOMMENDATIONS TO AVOID PROBLEMS

• Have the manufacturer recommend what type of lens will work with your application.
• Have the manufacturer install control and auto-iris connectors whenever possible. It is worth the small expense to not have to worry about installing a connector yourself.
• Become familiar with the equipment you will be using before you begin installation.
• Bench test all equipment prior to installation. If a unit is defective during bench testing you can get it replaced or repaired before you get to the job site.
• Take advantage of manufacturers technical assistance. Before sending your unit back to your distributor or the manufacturer, call for assistance. Many times your problem can be taken care of over the phone. Remember that most problems with any type of equipment are the result of user error and not a defect.
• Carry a fixed focal length lens with manual iris with you at all times. This will help you to at least determine if the camera is working properly and steer you towards trouble shooting the lens. Just because you have no picture that does not necessarily mean that the lens is defective.
• Carry a voltmeter. This will help determine that all your equipment is getting the proper voltage required.

The above information should help you avoid common mistakes and the trouble of returning equipment that is working properly. Again, remember to use the manufacturers assistance whenever possible.

David M. Craig - Technical Services Manager