Film-Tech Forum ARCHIVE: Metal Halide Lamphouse

This is topic Metal Halide Lamphouse in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=004898

Posted by Paul Trimboli (Member # 1509) on 05-16-2003, 08:14 AM:

Why are metal halides these days not uses in cinema projectors? They have solved the point light source problems, the colour temperature problems and the hours they can run for, normally around 2000-3000 hours for the brighter point source ones. So why are they not used? No need for a huge rectifier!? I know they have to run of a ballast with a sqaure wave output. I am thinking of trying one out inside and old arc lamphouse. What makes a Zenon the better light source?

Sam Hunter, if you read this how did you make your lamphouse without a point light source? Has anyone else made their own lamphouse for their home screening room?

Posted by John Pytlak (Member # 331) on 05-16-2003, 10:35 AM:

quote:
No need for a huge rectifier!? I know they have to run of a ballast with a sqaure wave output.

Since a xenon lamp can be powered by a compact switching power supply not much bigger/heavier than an HMI ballast, what's the advantage you are looking for?

Metal arc lamps were popular for smaller/portable projectors (e.g., MARC-300 lamp).

Posted by Gordon McLeod (Member # 33) on 05-16-2003, 02:34 PM:

The lumen output is still less on HMI type lamps than that of a Xenon and no they are not a popint source but a compact source. The plasma ball is about the size of a carbon arc crater not the pinpoint of the cathode tip. (remeber the light on a xenon system is on the tip of the cathode only)
The cost per hour is much higher as well on HMI styled lamps

Posted by Sam Hunter (Member # 1119) on 05-16-2003, 11:02 PM:

Phil,
All I can tell you is that I found the largest Ellipsoidal reflector I could find from a stage supply company and basically what I done was mimic the design of an ELC type lamp. I picked out a Halogen bulb that had the highest wattage/lumen/color temp and also had a small filament size. Then after assembling the reflector and lamp I began to experiment using a piece of steel placed in front of the assembly to check my light beam size to see where it focused at, this way I knew how close to mount it from the aperture.
If you are looking for a lamphouse I will not be needing this one any more and it will do the job and its nicely painted with an RCA symbol on it. Let me know if you are interested.