focus a camera with motorized zoom lens

[cro70 0]

Hi everybody,

 

I would like to know a procedure to focus a camera with a motorized zoom lens. The camera is FMX800 Extreme CCTV. Also, is there something special to do if I will use infrared illuminators at night? Should I focus this camera at night?

 

thanks a lot

[rapid 0]

You might check out http://www.cctvforum.com/viewtopic.php?t=160&highlight=focus+zoom+lens

 

Focusing is best done at night when the iris is fully open....when you adjust the focus at night, during the day the focus will remain constant. Neutral density filters can also be used during the day to accomplish similiar task if you are inclined.

 

As far as zoom lenses,

 

1. Set zoom lens to full wide position.

2. Set fine focus (front of lens) to midway of range.

3. Set backfocus to make picture in focus.

4. Zoom in (Telephoto) and adjust the fine focus for best picture.

5. Return zoom lens to full wide position and lens should stay in focus (track).

 

Extreme normally backfocuses in the factory before they are shipped out.

[cro70 0]

If you have a manual zoom lens, you have the barrels to do zoom and to do focus, in the motorized zoom lens case how can I do fine focus? Do you mean using the joystick? the backfocus is using the ring attached to the camera, right? and I guess the fine focus is done with the joystick control, this is really fine beacuase is just a small adjust.

[Cooperman 0]

cro70

 

The issue of setting up a cameras back focus is very straightforward, and is certainly something that has come up a number of times before on the forum.

 

For a motorised zoom lens, as rapid has already suggested, the first thing to do is to open the lens iris.

 

If it is a motorised iris, then you can hopefully do that with the controller. If it is an 'Auto Iris', your options are either to wait for very low light conditions (so the iris opens fully on its own), or use a dense neutral density filter or equivalent, to reduce the amount of light passing through the lens, and so force the iris to open.

 

Using the lens controller, set the Zoom to maximum telephoto, the Focus to Far, point the camera at an object in the far distance (maybe a tree on the horizon) and then adjust the back focus until the image becomes sharp on screen.

 

If you are intending to use Infra Red illumination, you may need to adjust the back focus slightly to allow the extra focus adjustment required to compensate for 'focus shift', which is present on most lenses being used at higher IR frequencies.

 

If you use an IR illuminator with a removable filter, you can easily hold that over the front of the lens, and then make any adjustment to focus under 'IR conditions'.

[cro70 0]

Thank you Cooperman, I have read about focusing a camera, and I do focus cameras almost every day but the lenses are not motorized and that is more complicated to me. Even more when is an expensive lens, I just want to be 100% sure what to do before I mess up.

 

Thank you very much.

[Securitymaster 0]

Talk to rory first, you won't regret it.

[cro70 0]

Thanks Securitymaster, I already did and you are right, I got just 2 answers but very value to me.