Film-Tech Forum ARCHIVE: lamphouse adjustment?

This is topic lamphouse adjustment? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Scott Balko (Member # 438) on 02-05-2003, 09:29 AM:

What is the best way to set the proper distance from the lamphouse to the apature plate if the manual doesn't state the correct setting?

Posted by Darryl Spicer (Member # 711) on 02-05-2003, 09:40 AM:

need a little more info for everyone to be able to reply correctly. Is it a console a regular lamphouse. What type of projector head is it.

Posted by Paul G. Thompson (Member # 655) on 02-05-2003, 03:40 PM:

Just call the lamphouse manufacturer. They should be able to tell you

Posted by Scott Balko (Member # 438) on 02-05-2003, 04:18 PM:

It's a Xetron XNH-2000 horizontal lamphouse on a century pedistal behind a century cc.

Posted by Dave Macaulay (Member # 813) on 02-05-2003, 09:45 PM:

There are working distances shown in the XCN Console support manual in the manual section here.
10" mirror - 19.5" working distance
11" mirror - 20.5" working distance
15" mirror - 31.15" working distance

Probably Xetron used the same mirrors in the console and lamphouses..? If you measure your mirror diameter and try setting the working distance as shown, you can probably see from the lamphouse position if it looks about right. Obviously the distance from lamphouse to projector has to be reasonable, probably 2 to 4 inches with a Century.

Posted by Paul G. Thompson (Member # 655) on 02-05-2003, 09:57 PM:

Edit: David supplied the information needed, so I'll retract my thoughts. [Smile]

Posted by John Pytlak (Member # 331) on 02-05-2003, 10:05 PM:

If you don't set the working distance correctly, you'll be "chasing your tail" to get good efficiency and uniform light distribution. Reflectors are essentially an eliptical shape, with only two points of focus --- the lamp plasma, and just beyond the film aperture. Setting the working distance wrong will make it nearly impossible to ever get the lamp in true focus.

Posted by Matt Close (Member # 996) on 02-05-2003, 11:06 PM:

John, is there a general formula based on reflector diameter to calculate the distance required?

Posted by Richard Fowler (Member # 893) on 02-05-2003, 11:55 PM:

There is not a general formula based on diameter since the curvature and depth of the reflector is part of the magnification and throw of the reflector. There are usually published specs on reflectors which is shown as F1 / F2....F1 is the focal point of the arc and F2, depending on the manufacturer is the throw as a point of light or more commonly in projection equipment the focal point of the cone of light which covers the aperture opening at peak efficiency.
Richard Fowler
Kinoton America Inc.

Posted by Scott Balko (Member # 438) on 02-06-2003, 09:36 PM:

I did find in the manual that they wanted 6 inches from the tip of the nose cone to apature plate. Now if I could just be certain that these are the correct cones. I have four lamps of this model and two different length cones. Go figure. You'd think they could give a spec with a little more definitive starting point. Kind of like giving your geographic position by saying there are three stars above you and you're directly under the brightest one. [Roll Eyes]

Posted by Gordon McLeod (Member # 33) on 02-06-2003, 10:22 PM:

If memory serves the xetrons used an Iconic reflector that had a compound curve to them

Posted by John Walsh (Member # 168) on 02-07-2003, 09:01 AM:

Don't forget, you could simply call Neumade/Xetron (203) 270-1100) and ask Bob Marr. I'm sure he will throw in a few good jokes, too... [Smile]

Posted by Gregory N. Jones (Member # 805) on 02-07-2003, 12:20 PM:

Scott,

Dave hit it right on the nose with those measurements but I will add that those working distances are measured from the rear of the reflector to the projector aperture.
In the past we supplied 1, 2 and 3K lamphouses and consoles with 10" reflectors but we switched to 11" reflectors because they put out much more light (about 6 foot lamberts just by changing the reflector!)
Adding to John's post, if you can't get a hold of Bob ask for me and if I don't know the answer I will find out for you guys.