Corporate Profile Varifocals Board Mount Lenses Manual Zoom Motorized Zooms Video Stablizer Lens Controller Contact Us

Motorized Zoom Demonstration Videos 30X / 50X / 100XIR
Price List
Specs and Drawings
How to Back Focus a Varifocal
Lens Glossary
Lens Comparison on
Camera/Lens Back Focus
Attaining the Required
Lens in Millimeters
Depth of Field
Image Sizes
How to Trade Down
C-Mount vs. CS-Mount
Article: Behind the Lens
Credit Application


It never fails. You are up on an 80 foot pole 40miles from the shop and the lens won't work. Many times the problem is the result of an installation error. Although a lens is not a highly complicated device, many installers are not familiar with the parameters of installing a lens and will return a unit rather than ask for help. The following should aid you in preventing common installation problems and help you determine if a lens is actually defective.

Lens Types

There are two types to auto-iris lenses currently available. "DC" type lenses receive their DC iris control voltage directly from a circuit in the camera. "Video" type lenses contain a circuit (onside the lens) that converts a video signal level (from the camera) to DC iris control voltages.

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

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

Check camera options for lenses
Keep in mind that some cameras offer options for both video and DC type lenses. Some cameras may require that you flip a switch to select the required output for the lens you are using. A video type lens will not work if the camera is set up for a DC lens and vice versa. Other cameras may require that the iris connector be wired differently for each type. Refer to the camera instructions for information on proper set-up.

Isolate any unused wires
Make sure that you isolate with tape or shrinkable tubing any unused wires of the iris cable. Some lenses offer special options which are not normally used and the lens may not function if these wires touch each other or the shield of the cable.

Zoom Lens Problems

Verify that the control connector is wired properly.

Identify the color codes for lens and controller
Identify the color codes for the lens and controller.

Is the lens getting the proper voltage?
Using a voltmeter, verify that the lens is getting the proper voltage. Some manufacturers offer lenses that work with 6 volt or 12 volt systems and may not be compatible with your system. Make sure that the lens and controller are designed to work together.

Lens operates but the picture is not in focus.
Did you perform the back focus procedure? A zoom lens not set-up properly will not be in focus or will not remain in focus when zooming.

Back Focus Procedure
    1. Open iris to maximum. Use a filter if light is too bright.
    2. Set focus to far, zoom to wide angle.
    3. Adjust camera back focus only to obtain a clear picture.
    4. Zoom in to an object at least 15 feet away.
    5. Adjust lens to focus only to obtain a clear picture.
    6. Repeat above until lens remains in focus while zooming.
Are lens and mounts compatible?
Make sure that the camera and lens mounts are compatible. Refer to the above section on C/CS-mounts to check compatibility. Do not use more than one 5mm spacer when putting a C-mount lens on a CS-mount camera.

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 circuit inside the camera, 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 voltometer, measure th 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?

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.

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.

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.

Tekstar Optical, Inc.  |  75 Lackawaca Hill, Napanoch, NY 12458  | 
Phone/Fax: 845-647-5367 (LENS)  |  Cell: 516-582-3458