This is topic Using metal halide bulbs for film projection in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Matthew Bailey (Member # 601) on 05-10-2002, 11:32 AM:
I want to use a lamphouse but I don't want to screw with xenon bulbs or carbon rods. I want to build a lamphouse that uses metal halide bulbs. Some of these bulbs are used in street & security lighting.
What wattage of bulb would I need,etc.?
Posted by Scott Norwood (Member # 30) on 05-10-2002, 11:46 AM:
This won't work, at least for color prints. Metal-halide lamps (and most of the other types used for security lighting) are not full-spectrum light sources. Colors will look very odd at best.
Posted by Michael Rourke (Member # 1142) on 05-10-2002, 11:46 AM:
Metal Halide bulbs glow red and I don't think they would produce enough light. Also, all High Intensity Discharge bulbs take about 5 minutes to warm up to full light output.Mercury Vapor lamps glow a bluish green, and High Pressure Sodium glow a bright yellow. HPS lamps are the ones used in street lights.
Maybe you'd be better off using HTI bulbs even though they are more expensive they would be better suited for this application.
Posted by Michael Rourke (Member # 1142) on 05-10-2002, 11:56 AM:
Scott is right, Carbon and Xenon are used in movie projection because they both run close to 6000 degrees Kelvin which looks like natural sunlight. This enures the proper color hues on screen.
Posted by John Pytlak (Member # 331) on 05-10-2002, 12:44 PM:
To see how BAD mercury vapor or sodium vapor lamps are for "color rendering", just look at some critical colors (like a Macbeth Color Checker Chart) illuminated by streetlights. A red automobile looks almost gray under a mercury vapor lamp, which has very little light output in the red portion of the spectrum.An HMI lamp does have possibilities, but it will still need a ballast and won't cost much less than a comparable xenon lamp made for motion picture projection.
For a small home screen, has anyone experimented with the new xenon lamps made for automobile headlights as a light source?
http://www.sylvania.com/xenarc/prodinfo.htm
http://www.legend.org/performance/mods/lighting-1.html
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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion
Posted by Brad Miller (Member # 2) on 05-10-2002, 03:47 PM:
Matthew, this isn't a very elegant solution, but a cheap one that will work if you really do not want a xenon or carbon lamphouse.Go to flee markets and look for old 8mm home movie camera lights. There is one inparticular called the "Sun Gun" that you will normally see selling for $5 or less. It takes a 750 watt halogen lamp and has it's own little reflector built into it. The bulbs are cheap (less than $10) and it is an instant on/off and will produce an acceptable amount of light provided your screen isn't more than say 8 feet wide. Make sure you use a DBDT switch to control your motor and the light so you don't ever accidentally stop the projector motor and leave the lamp on. Also, make sure you have a fire douser in your projector.
Like I said, it isn't the best solution out there, but from the sound of your project, it'll get you by.
Posted by Steve Kraus (Member # 476) on 05-10-2002, 03:53 PM:
On the contrary, I think metal halide lamps have good color balance. I don't think they would work well as a projection bulb because they are not a point source which would make efficient reflector design almost impossible. And on the whole they would not be as cost effective as xenon. As regards the spectrum of halide lamps, note that these lamps are very common sources of illumination on movie sets, often under the trademarks HMI, CSI, etc. You also will see them used for indoor lighting in many department stores, home centers etc. Color balance may not be as even as high pressure xenon but it is quite good nonetheless.
Posted by Jerry Chase (Member # 660) on 05-10-2002, 04:07 PM:
I like Brad's "Sun Gun" idea, but IIRC, my dad had one and the lamps had a short lifespan. Along similar lines, the tugsten halogen prefocus medium base lamps for stage work have some models with a 2000 hr life and 500 to 750 watt draw at 120 vts. They also have a CRI of 100.PDF document here
Posted by Gordon McLeod (Member # 33) on 05-10-2002, 04:23 PM:
There are metal halide and the then are metal halide
The ones used for light sources on films are a type of metal halide called HMI or CSI lamps the CSI has a lower color index whereas the CID is a daylight spectrum.
The problem is they are AC arcs and as such have a 120 HZ flicker that will beat with the projector shutter.
On film production they use specially designed ballasts that are a square wave output. For TV they use regular reactor ballasts as the sync is the same
Also they are not very efficient to design a optical train around as they have a rather large plasma ball
Posted by Jeff Stricker (Member # 224) on 05-10-2002, 04:23 PM:
John P. - the xenon headlamp idea sounds like an interesting one. However, I wonder if 35 W of xenon produces as much lumens as my current 360 W quartz halogen lamp? This might be worthwhile tinkering with.Anybody have any idea if these things run right off 12V DC? Any special circuit required to strike them? Also, my guess is they are designed to spread the light over a fairly large area (as required for a driving lamp) and I'm not sure if you can reduce the beam successfully using a condenser lens scheme?
Lots of questions, so few answers.
Posted by Luciano Brigite (Member # 1104) on 05-10-2002, 11:20 PM:
I was thinking about asking for some advice here about using these bulbs instead of xenon or carbons but decided to ask around and found out that a few theatres here in Brazil,the ones I heard being in the same state I live, switched to HMI bulbs with the same wattage of xenons they were using and the results were very good. I believe it's not really a valid information since I heard it from the tech who made the changes.
I saw some of these bubls in action and think the color temp is about the same as xenon or daylight and i'm thinking about using these bulbs in my lamphouses too since I can't get carbons for a decent price.
I checked some informations about the HMI in the UShio's catalog ( theu call this kind of bulb UMI, Osram calls it HMI)
and came out with the following: ( the values bellow are from
575, 1200 and 2500 Watts bulbs, respectively)color temp= 5600K ( to all bulbs)
Arc gap= 7mm , 10mm (1200/GS) 7mm (1200/HB), 14mm ( they have two bulbs in the 1200 W range)
Luminous Flux= 49000lm , 110000lm , 240000lm
Average life 750Hs ( 575 and 1200 W) 500Hs (2500W)
The Osram's catalog gives some different information about the same bulbs, I don't have it in hand atm but the color temp was about 6000K for 575 and 1200W and 6300K for 2500W. Don't remember the arc gaps for the Osram bulbs, sorry.
Hope this helps ...
Posted by Stefan Scholz (Member # 147) on 05-11-2002, 06:08 AM:
Metal halides actually give a good color rendition, if used for stage lighting during photography or filming.
For motion picture purposes, you do require a point source of white color. Even with "color correct" metal halides, the different parts of the spectrum do not originate from a single point, different gases and rare earth components exhibit different spectral lines at different points of the arc.
Osram introduced a special 400 W HMI metalarc lamp for narrow gage film projection, about 10 years ago. Arc was the only suitable way to get brighter images, as the filament of a standard bulb reaches the size of the picture gate @ 250 Watts (16mm) and 100 Watts (8mm), therefore any increase in lamp size would not relate to higher light output.
HMI seemed an ideal source, 400 Hz square wave AC supply to be quite small and lightweight, as well as assuring long enough bulb lifespan, superior color rendition and arc stability as well as life compared to Marc 300 DC lamps.
Major problem was the uneven spectrum within the arc. The designer group ended up creating a lamp within a special ellyptical mirror consisting of at least 3 different focal planes, each for every color part of the spectrum. The technology of the mirror was anything but simple, and the light output extremely high. The lamp/ supply unit proved quite well in Bauer P8 machines. Still, the red end of the spectrum wasn't as good as with Xenons, lacking deep red content. The same bulbs and supply units are now standard in outdoor lighting and shop display window lighting applications, and sell, despite their complicated process, pretty reasonable due to quantities. In this type of application, the large reflector, and non existing focusing to a single point does give a stunning color rendition of >99% white daylight, with very low energy consumption.
In 1994 I was experimenting with the 16mm type 400W lamp, and integrated that into my Microcine 35 portable. The light output was comparable to a 1600 watt Xenon, but due to the lacking correct focusing of the optimized for 16mm mirror, the light color was not really nice, faces had an orange green touch, for instance. Still, for the purpose of making outdoor screening in a garden and town square it proved to work quite well.
And the nice fact at that time was: single phase 8lbs supply, no heavy rectifier.
Today I would only go for Xenon, better light, and rectifiers are lightweight, too. The most recent example I found was 20 lbs, 1o kW cont. out of a 40 Amp/ 230V singlephase circuit.
Posted by Steve Kraus (Member # 476) on 05-11-2002, 11:21 AM:
This isn't anything new, is it? Are not the GE Gemini & MARC and Sylvania ColorArc bulbs (all prefocused dichroic reflectors built around a small quartz arc tube) halide lamps?
Posted by Randy Stankey (Member # 64) on 05-11-2002, 10:33 PM:
I'm thinking along the same lines as Brad. Either one of those Sun Guns or a theatrical/stage lighting unit like a Leko, etc.We use ETC "Source Four" lights here on our stage. They can be fitted with a 500 watt or a 750 watt lamp. The lamp can be aligned or focused within the reflector just like a xenon. You can get different lenses for them to condense the light into different patterns. (They go by beam angle in degrees... 5º, 10º, 19º, 26º, 36º or 50º) They have shutters to cut the beam. You can adjust the barrels to get a "fuzzed" or a "hard" edge and you can even put iris units in them.
OK... So, you're probably not going to go out and spend several hundred dollars to get a light like that but I think you get the general idea. Maybe you could go around to some schools and scrounge one of their old units in exchange for something they need.
Posted by Jason Black (Member # 684) on 05-12-2002, 01:03 AM:
Randy,I see you've moved from G'boro...?
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The early bird may get the worm, but the second mouse gets the cheese!
Posted by Matthew Bailey (Member # 601) on 05-13-2002, 08:58 PM:
I am wondering if a homebuilt 1000 watt lamphouse using five 200 watt household bulbs either frosted or clear,preferably clear would work.
Posted by Randy Stankey (Member # 64) on 05-13-2002, 09:24 PM:
I suppose you can do anything you want but using a bunch of bulbs like that is going to be a big hassle.You have to make a fixture to hold that many bulbs that won't overheat... won't blow a fuse... won't electrocute somebody... will put out light in the correct "pattern" for the projector (a cone-shaped beam)... and is still small enough to fit in your booth.
There's the matter of the reflector... How are you going to make a parabolic (dish-shaped) mirror that has five holes in it for the bulb bases to go through yet still reflect light well enough to illuminate the screen?
Sounds like too much trouble to me.
But there's an old saying: "Nothing is impossible... Some things just take longer." 
***********
Well, Jason, I liked the job and the company was OK , however, being on the road for 6 days a week is bad enough but when you don't have any family to come home to at the end of it all you start to lose your sense of humor about things. I decided it was time to come back home. Now I work full time at the college where I was "moonlighting" before I left.
Posted by Gordon McLeod (Member # 33) on 05-13-2002, 09:47 PM:
I think you are wating your time re inventing the wheel
You would require a cloverleaf style convergance lens to refocus the multiple lamps ( all of us who delt with the norleco horizontal xenon with that lens will testify to the grief it can cause if not properly aligned)
With the vast amount of good surplus equipment out there I can't fathom a reason to go on this quest other than to attack some windmills 
Posted by David Koegel (Member # 25) on 05-14-2002, 07:50 AM:
Matthew had to have been kidding with his last suggestion 
Posted by Matthew Bailey (Member # 601) on 05-15-2002, 07:24 PM:
I suppose each of the five 200 watt bulbs would have it's own reflector &/or lens all of whitch would be converged onto the snood.
Posted by Evans A Criswell (Member # 381) on 05-15-2002, 07:57 PM:
It seems that if one were to attempt to use metal halide lamps for projection, it would be best to use a single 1500W bulb, since such a bulb produces 155000 lumens (at least they did in 1981 when I learned about various types of lights). Using such a lamp may require a special reflector. I'm really curious if such a lamphouse could be used effectively? 1500W metal halide lamps are the size used to illuminate most baseball and football fields these days.------------------
Evans A Criswell
Huntsville-Decatur Movie Theatre Information Site