Question: What is ALC and Level?

[genm79 0]

Good day to all,

 

I am new at this and would like to ask about the following.

 

I have recently come across a Lens from Fujinon and it had 2 rotary switches on the side of it.

 

One is named ALC and the other is named Level. I was wondering if anyone can explain to me what it means and how to work with them. Or you could simply point me to a webbie for me to research.

 

Model: C22 x 23B - V41 (Fujinon)

 

Thanks in advance.

[survtech 0]

That would be a video auto-iris lens. Although video auto-iris lenses are still made and sold, DC auto-iris lenses are much more common today. A video auto-iris lens uses unfiltered baseband video from the camera to adjust the the lens' iris via active circuitry in the lens itself. It must be attached to a camera that has a suitable output connector.

 

The more common DC auto-iris lenses have no active circuitry in the lens; the camera would contain that circuitry.

 

The ALC adjustment would control iris compensation for bright spots within the field of view either by exposing for them in particular (peak) or by taking an average across the entire scene. The Level adjustment would adjust how much the iris closes under bright lighting.

[genm79 0]

Thanks for the info.

 

I have some more questions to ask.

 

1.

It must be attached to a camera that has a suitable output connector.

You mentioned suitable output from the camera. Currently I am using Panasonic WV-CP480.

 

The output of the camera is only Video out. Should I get another one? If yes, what would you recommend?

 

2.

the lens' iris via active circuitry in the lens itself

Can you explain further with regards to this?

 

I mean how do I check if my lens comes with this 'iris active circuitry'?

 

Is there any tech jargon I should looking at the brochure?

 

Thanks again.

[Soundy 1]

It must be attached to a camera that has a suitable output connector.

You mentioned suitable output from the camera. Currently I am using Panasonic WV-CP480.

 

The output of the camera is only Video out. Should I get another one? If yes, what would you recommend?

The lens should use the same connector as a DC-iris lens... that would be little black square in this picture:

 

You would also have to go into the camera's menus (using the buttons under the slide-back cover in this same picture) to tell it to use video-iris mode instead of DC iris.

 

the lens' iris via active circuitry in the lens itself

Can you explain further with regards to this?

 

I mean how do I check if my lens comes with this 'iris active circuitry'?

 

Is there any tech jargon I should looking at the brochure?

 

Thanks again.

Those two adjustments on the lens tell you that it uses video-iris.

[genm79 0]

You would also have to go into the camera's menus (using the buttons under the slide-back cover in this same picture) to tell it to use video-iris mode instead of DC iris.

 

Thanks.

 

I have changed the drive mode to video iris. But I have encountered a new problem.

 

Once I set it to video iris, the lens iris will auto close. Now I cannot open the lens iris.

 

Help!

[Soundy 1]

Did you change the ALC and Level adjustments on the lens, as survtech indicated?

[genm79 0]

Thanks to Soundy and Survtech, most of my problems have been solved.

 

Well the rest will have to be for the professionals to check. Thanks guys.

 

Hope I wasn't too much of a bother. ^^

[genm79 0]

Hi Guys. Sorry to bother you all again. Just got my lens back from the service center last Friday.

 

The peeps at the service center says that everything is to spec and working fine.

 

But when I tried to do some adjustment to the ALC switch on the lens, nothing happened.

 

So I am wondering if I have mistaken what the ALC function is for. So here is my question.

 

1. What does ALC stands for?

2. Under what conditions is the ALC used?

3. In the 'Prefect' situation, what am I suppose to see when I switch the ALC to:

i: Peak

ii: Average

 

Thanks in advance again guys.

[survtech 0]

See here: How to set an auto iris lens

[genm79 0]

Could someone recommend me some test that I can perform on the system that I am having to check on whether my ALC and Level are working.

 

Camera: Panasonic WV-CP480

Lens: C22 x 23B - V41 (Fujinon)

 

I am not using any control box at the moment. I am adjusting the potential meter direct on the lens itself.

[survtech 0]

#5 or #6 Welding Glass. Available at most welding supply stores.

 

 

In bright daylight or brightly lit area, place welding glass against lens so that all light goes through glass and look at picture. Remove and replace welding glass and double check that image remains good. With glass in place, iris should open and when glass is removed, iris should close. If not, iris cable is not connected correctly or is working improperly.

 

Adjust focus with glass in place. Remove glass, adjust lens iris controls for best picture in brightly lit scene. Go back and forth a few times to check proper operation of iris.