Computar Motorised Zoom Lens

[Spacedout 0]

Hello,

 

I am a complete novice with with CCTV cameras and lenses and to be truthful I only use them for broadcasting as one of my hobbies is video astronomy. Low light cctv cameras are perfect for this but as I say it is a hobby so my knowledge of the inner workings with this type of equipment is seriously lacking!

 

So with that said, I am hoping someone can help me work out how I can make good use of a Computar lens I have just picked up of Ebay. I bought two lenses and it seems one is DC auto iris and the other (the problem) is video auto iris. The dc lens is fine as I have a plug this will attach to my camera and bingo I have a picture but the video auto iris does not and has some other kind of connection. Please see images below.

 

 

 

 

 

So can anyone please tell me how I can connect this to a normal cctv camera so I can open the iris. The other question is, would anyone know where I could get replacement buttons of the ALC and level. You may have noticed in the image these are missing.

 

Okay I hope I'm making sense and I hope someone can help.

 

Many thanks

 

Karl

[Spacedout 0]

Ok this may not be as straight forward as I hoped. Would anyone know then how I open the Iris on the lens? For what I plan to use it for I do not need the iris so it would be no problem to have this open all the time as I'm only using the lens at night.

 

Many thanks

[survtech 0]

Not the easiest thing to do.

 

Converting CCTV lens from video auto iris to DC auto iris

[Spacedout 0]

Thank you Survtech I was beginning to give up hope with this one. I had a quick look at the link but I will need to study it further as I have no experience at all with electronics. However, someone has done it so I'll need to learn I'm not sure if it makes any difference but the camera I plan to use with it is an SCB-4000 which is video or dc. As I say I know nothing about this sort of thing but I assumed if I connected an iris plug to the red, black and white wires following the standard video auto iris wiring diagram it would work but I guess it's not that simple? Is there an easier solution and what is normally done with this kind of lens?

 

Thanks again for responding as I really would like to put this lens to good use!

 

Much appreciated

 

Karl

[Horizon 0]

Hi SpacedOut.

 

That's a seriously nice lens - 30x zoom!

I've got a couple of older lenses similar to this one (only 10x zoom), but mine use a motor to drive the iris, I think yours uses a galvanometer type movement.

 

Is this the data sheet for the lens? http://www.rmaelectronics.com/content/ComputarGanz-Lenses/H30Z1015AMS.pdf

 

Yes, connecting the red, black, and white wires to a camera that supports video auto iris should work fine.

 

Otherwise, you can probably trick the lens to fully open the iris. I'm assuming the iris is closed at the moment?

I haven't tried the following, but in theory it should work...

The iris cable should have four wires inside it:

Red, black, white, and yellow.

For the purpose of this experiment, we'll power the iris from a 9 volt battery; the kind you use in a smoke detector or remote control.

Connect the red wire to the battery positive, and both the black and white wires to the battery negative. Ignore the yellow wire. In theory, this should open the iris.

 

What happens is that the "video auto iris" monitors the video signal, and adjusts the iris so that the video signal from the camera sits at a particular level. Kind of like cruise control on a car.

What you've done with the battery is that you've powered up the iris controller, which is monitoring the video signal on the white wire. Since there is no signal there, the controller commands the iris to open so that the camera image becomes brighter, and the video signal stronger. Since the signal can't get stronger, the iris fully opens.

 

Disconnect the battery, and see if the iris stays open. If it closes, then its using a galvanometer style movement, with a return spring. You'll need to permanently apply power to keep the iris open, in which case you could replace the 9 volt battery with a 12 volt plug pack, or anything between 8.5 volts and 16 volts - don't exceed 16 volts or you'll wreck the lens! Also, make sure the plug pack is direct current (DC), not AC.

 

If you want to use the auto-iris function, you could probably feed some of the composite video signal out of the camera into the white wire. It's slightly more complex, and probably not necessary if you're using this lens for astronomy.

 

BTW, the "level" and "ALC" don't use buttons, they are trimmers used to adjust the image brightness, and how sensitive the iris is to bright objects in the image (peak and average). The buttons you are looking for will be dust caps.

[Spacedout 0]

Thank you Horizon and yes if I can get the Iris open this will be a very nice lens indeed! Yes that was the data sheet too.

 

I just tried the 9V battery as you suggested but this did not work unfortunately. The lens does make a little noise but it's almost as if something is stuck or there is not enough power if this makes sense? I've taken a couple of images of the lens zoomed in and out, just in case I'm missing something.

 

[Spacedout 0]

Sorry posted before I'd finished! Okay so the 9V did not open the Iris, would this mean the Lens is broken or I need to try something else?

 

Thank you so much for your help I'm completely lost with this but would really like to get this thing working if possible!

 

Best wishes

 

Karl

[Horizon 0]

Hmmmm.

It might be that the battery isn't "fresh" enough, and the iris is stuttering. It should be nearly silent when operating, and will take a couple of seconds to fully open.

I doubt the lens is faulty - it looks very clean and well cared for.

I think I have one of these stashed away somewhere (not 30x sadly). I'll see if I can dig it out tonight and have a play.

 

Your other option is to replace the 9v battery with a 12v plug pack. The battery is best to start with, because wiring mistakes are likely to be less damaging to the lens. The lens is designed to be powered by 12v from the camera.

 

The simplest solution for you is to find someone to solder an iris plug onto the cable. It's pretty much guaranteed to work then, but it is fun to experiment

[Spacedout 0]

Oh dear I'm getting a bit twitchy, I tried a new 9v, then a 1.5 followed by 12v and still nothing! Thanks for your help Horizon on this I'll be gutted if I can't get to use it! I did try soldering an iris plug on using the black, red and white wires leaving the 4th pin free. I followed the wiring diagram for video auto Iris but this did not work though this could just be my rubbish soldering. If the battery trick does not work is there anywhere I can send this lens to be checked out and if possible repaired?

 

Thanks again very much appreciated!!!

 

Karl

[Horizon 0]

Hi Karl.

I had a look at some old (1980's era) video-iris lenses, and the both opened their irises when I connected a 9 volt battery across the red and black wires.

 

The only modern Computar motorised zoom I have uses a motor-driven iris. It acts as a remote controlled manual iris, with no automatic features. I think it is a T10Z0612MSP.

The connection to the iris on my lens is through the white and brown wires. A 9 volt battery connected positive terminal to white opens the iris, connected positive to brown closes it.

 

The only other problem I can think of with your lens is the yellow wire. It's for a remote ALC control, and might need to be connected. What's written on the label attached to the iris cable on your lens? What does it say about the yellow wire?

[Spacedout 0]

Hi Horizon,

 

Thank you for doing that I'm really grateful! I'm not sure if the yellow wire is the issue because when I got the lens it had a box on the iris cables with a dial as attached. The only wires used were the black, red and white. The box has a holder for a 9V battery and two pins that then must of connected to a camera or remote control I'm not sure. Does this look familiar to you? I'm now strongly suspecting a fault somewhere and will be emailing the person I bought it off tonight. I would send it off to be tested and repaired but I have no idea who could do this sort of work short of sending it to Computar themselves!

[Spacedout 0]

I need to get used to this format Here is the inside of the box, 3 wires in and two out.

 

 

 

Thanks again

 

Karl

[Spacedout 0]

Okay, I tried soldering a new plug today and still no joy! I've now contacted this company for a possible repair and they quoted £325 to fix it. I'm tempted as I seem to have run out of options but I do wonder if I simply not doing something right! Anyone use this company before or know of another who may be a bit cheaper?

[Horizon 0]

Hi Karl.

That box acts as a remote control for the iris.

The dial is attached to a variable resistor (although I haven't seen one that looks quite like that), which combined with the fixed resistor, allows the voltage on the white wire to vary between zero volts (iris open) and probably around 1 volt (iris closed).

Have you tried connecting the lens to these red, black, and white wires, and adjusting the dial?

[Spacedout 0]

Hi Horizon,

 

That is interesting, so basically the lens was not connected to a camera before if that is the case. I did reconnect the box recently and put in a 9v battery but the iris did not open. However, there are two connection points that stick out at the top of the box and I wonder what that was connected too? I wonder if you need the battery and another power source to make the remote control work?

 

Thanks again

 

Karl

[MaxIcon 0]

If this were mine, I'd take the cover off and see what it looks like inside before I'd send it out for an expensive repair. This would let you track where the wires go and see if there's anything open or disconnected. This lens should have 3 motors - zoom, focus, and AE - so that may clear up which wires do what.

 

I've got a smaller version of this at home with a control box, but it's been a few years since I've messed with it.

 

I've converted a few auto-iris lenses to use with non-auto-iris cams by removing the auto iris drive assembly. This is easy on some lenses, and tricky on others. You then have it fully open all the time, which can be an issue depending on the app.

 

If you do take it apart (you'll need some tiny screwdrivers), take pics at each stage so you can get it back together again.

 

Also, this appears to be a C mount lens, so if you've got a CS mount camera, you'll need a C to CS adapter for it.

[Spacedout 0]

Hello MaxIcon,

 

Thank you and I did remove the cover but when I saw the inside of the lens I though better off it. It is a serious piece of engineering and I knew if I stripped it bare it would have been game over. I did manage to check all the wires and everything seemed intact so I really have no clue what the issue could have been. However, I have now sent it off to be checked and repaired if possible so let's see. If they can repair it the cost is pretty steep but the cost of one of these lenses new is a lot of money and so it will be worth it.

 

Thanks for the advice, very much appreciated.

 

Regards

 

Karl

[Spacedout 0]

Hello All,

 

A little update on this problem - Finally and after way to much money I now have the lens working apart from one important aspect... Focus! Currently the best focus I can get is by using a 5mm c-cs mount adapter. The problem I have is I can not get a decent all round focus. For example, at night if I point the camera and lens to my shed about 10 metres away the focus is just off. This is with both the zoom and focus of the lens at the furthest and widest point. If I zoom in a bit and tweak the focus I can get it sharp but why not at the widest field or view? Then if I point the lens and camera at the stars the focus is well off but if I zoom in again I eventually get focus. Please have a look at this video as an example.

 

I have tried various spacers but no joy. If I hold the camera to the lens manually I can get it. It seems as though the camera chip needs to get in a fraction further but how?? Is there such a thing as an adjustable c-cs mount adapter or a perhaps a much more straight forward method?

 

Many thanks

 

Karl

[Horizon 0]

Hi Karl.

You probably need to adjust the back-focus on the camera. The adjustment allows the camera and lens to stay in focus when zoomed in and out.

The procedure is something like this: http://www.vicon-security.com/Collateral/Documents/English-US/support/LensBackfocusAdjustmentPr.PDF Note that it may take several adjustments at max. zoom-in and zoom-out to get the back-focus adjusted correctly.

 

BTW, so did they say what was wrong with the lens?

[Spacedout 0]

Hi Horizon,

 

Thanks for the info. I had to use a different camera in the end as there was just not enough play with the one I was using to adjust the back focus. Still all sort now and the lens is working exactly as I'd hoped. As mentioned before I wanted the lens for astronomy. Have a look at this short video of the lens zooming in on 2 galaxies, M81 and M82 -

 

Not entirely sure what was wrong but they said they had to strip it down a replace some parts and gave it a general service. Whatever, it works now and works very well indeed

 

Thanks for you help, very much appreciated.

 

Karl

[Spacedout 0]

Hello All,

 

As much fun as I've had with these lenses I'm now moving on to other things and in reality these lenses will be better off being used for what they were intended, security! So I'm now trying to shift them if anyone is interested please send me a PM. I was going to put them in the classifieds but I'm not a regular here and rightly have not earned that right yet!

 

Best regards

 

Karl