This is topic Reflector Materials; Are there any data about them? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Michael Moore (Member # 3867) on 06-15-2007, 08:54 PM:
 
I have been told by some people that glass is far superior to metal when it comes to reflectors. I have also been told that metal is better. However, no mater what I have been told the people telling me this has yet to show any data showing the difference in light output between these two materials.
I sure some light is lost with glass; however is infrared an important part of the spectra.
I have access to a real time diode array spectrophotometer. I can take reading with the fiber optics and get a spectra for the light output. And I can get lumen output as well only thing is I only have access to glass reflectors.
Has anyone taken these kinds of readings? Anyone have papers or journals on this kind of stuff?
Mike
 

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Posted by Monte L Fullmer (Member # 2797) on 06-16-2007, 03:41 AM:
 
Dichronic (red) mirrors are great since the heat goes through the glass while the light is reflected, but the simple downside is that these mirrors are pricey and if a bulb blows, so does the mirror.

Metal mirrors reflects everything out -from infared to ultra violet through the lamphouse, but the metal acts like a big heatsink absorbing some of the heat from the bulb before that heat goes through the machine. Also, if the bulb blows, the quartz shards might just scrape up the mirror some to where it can really ding it up, but the mirror doesn't destroy itself if it were glass.

With dichronic mirrors, the light output is greater than black chrome metal mirrors - why in the old days of 3-D with carbon arc light, lamphouses were equipped with these dichronic mirrors to get as much as the light out as possible than what the old silver plated glass mirrors would yield.

I work in a drive-in that the lamphouse has a dichronic glass mirror and can easily tell that I'm getting better light out than if this lamphouse would have a metal mirror.

Do a google search on this topic...might find something.
 

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Posted by Robert Minichino (Member # 3495) on 06-16-2007, 08:16 AM:
 
It's "dichroic" These mirrors are also called "cold mirrors" because they reflect visible light while letting IR pass through without reflecting it.
 

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Posted by Mark Gulbrandsen (Member # 72) on 06-16-2007, 08:59 AM:
 
No Monte, That same company's metal mirror is far more efficient than their glass mirror! I have tested them side by side. That glass mirror design is good but probably at least 40 years old.

Glass is not inherently more efficient than metal, its all in the efficiency of the design itself. The thing that all dicro glass mirrors should provide is less heat on the film.

Mark
 

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Posted by Steve Guttag (Member # 268) on 06-16-2007, 09:40 AM:
 
It is more than just the lack of heat the glass mirrors provide...it is also light uniformity. Using Kinoton's alignment projector one can easily see the imperfections in the metal mirrors as compared to glass. Heck...even using a taught string one can see where metal mirrors are often not completely uniform.

However, the design of the mirror (its shape) and how it interracts with the xenon lamp AND the lens have have a huge affect on how much visible light is projected to the screen. I've found some metal mirrors that do substantially better with a 5KW lamp versus the same company's 4KW lamp...yet I've found that another company's glass mirror does better with the 4KW lamp as in MORE light was had with a 4KW lamp than the 5KW lamp even though there was more light in the lamphouse with the 5KW lamp.

I have no doubt that this is why Technilight (or however its spelled) specifies specific lamps (make and model) to be used with their mirrors and not just any old lamp...even if a competitor's lamp is of high quality. That whole optical system must work together as a team.

I'm right now doing a test for ASL...their 4202 series lamps are yielding 30% more light than either their 4000 watt lamp or other 4000-watt lamps in a Kinoton Universal 2-7K lamphouse. Do I think that would translate into an equal improvement in a Strong or Christie lamphouse/console...I can't predict it (though it may certainly be worth a try). Different designs work differently.
 

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Posted by Mark Gulbrandsen (Member # 72) on 06-16-2007, 12:50 PM:
 
Steve,

Please let us also know how the reliability of the ASL lamps compares to that of say Christie and Osram. Over the years I've typically found that higher output lamps have shorter life spans. There is a trade off of some sort in there to get that extra light.

Also the Teknilight mirror doesn't necessarily have to work with specific lamps although it will do better in critical cases with the short gap lamps. On the BYU Eastman it was just a standard short 2kw lamp that was used to achieve 27fl.

Mark
 

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Posted by Louis Bornwasser (Member # 3063) on 06-16-2007, 02:02 PM:
 
Note: upon explosion, ALL reflectors are damaged enough to change out. It is an illusion that glass breaks and metal does not. The only safe plan of attack is to have a spare reflector.

BTW: the reason we went to metal is that the "deep dish" reflectors of the 70's could not be reliably moulded in glass. Now that reflectors are less deep, we should go back to the dichroic glass reflectors for heat reasons. Louis
 

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Posted by John Pytlak (Member # 331) on 06-16-2007, 04:27 PM:
 
On a metal mirror with a dicroic coating, the metal of the mirror itself acts as the heat sink, where the unwanted IR energy is absorbed. Therefore, be sure the mirror is properly cooled to maintain efficiency.

With a "glass" mirror having a dicroic coating, the IR goes though the back of the mirror, and there is usually some sort of metal shield or other heat sink behind it.

You can also use an additional flat "glass" dichroic mirror that reflects the IR to a heat sink. Some of the vertical lamp lamphouses reflected the light off a flat metal dichroic mirror, and the IR was absorbed by the metal mirror, which needed to be properly cooled to be effective.
 

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Posted by Mark Gulbrandsen (Member # 72) on 06-16-2007, 07:34 PM:
 
Hi John!
The heat filter thing is still available on all larger wattage lamphouses to help filter out any excess UV. Its an option on most lamphouses...Strong, Christie, and I would assume Kinoton. The thing about the heat mirrors as used in Strong's gear is that they just aim the reflected heat straight back at the end of the bulb.

Mark
 

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Posted by Louis Bornwasser (Member # 3063) on 06-16-2007, 08:28 PM:
 
One of the funnier stories about heat in xenon involves the Christie CH=20 series. The original lamp used a lens in the "snood" (nosecone). Bulbs failed due to heat being reflected back onto the extreme front end of the bulb. Rather than rethink the optical system, they air cooled the end of the bulb with a glass air tube and radiation shield. It worked, BUT.... Louis
 

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Posted by Monte L Fullmer (Member # 2797) on 06-16-2007, 09:02 PM:
 
Dang, Louis - I still service a cinema that still uses those old CH-20 "snood" consoles with the anode air tube/shield support...but no lens in front now.

They're lucky to get warranty on a CXL-20 bulb since either the chrome wire arcs across the back of the mirror and makes for hard striking, or just heads to bad flickering from where I think that the caps needs replacing.

These consoles are ancient years old.- Monte
 

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Posted by Mark Gulbrandsen (Member # 72) on 06-16-2007, 09:56 PM:
 
Monte... OF course there's an easy upgrade path for those consoles that does not involve replacing the actual console.

Mark
 

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Posted by Monte L Fullmer (Member # 2797) on 06-17-2007, 02:28 AM:
 
Yea, called the Kelmar upgrade...(and this could swing into that other topic..), but, no-go on this for right now with them ...lol
 

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Posted by Louis Bornwasser (Member # 3063) on 06-17-2007, 06:09 AM:
 
If it's a console, you actually have 3 options:

1. The "strong" reflector kit, originally developed & marketed by Hadden.

2. The Phoenix kit by Christie.

3. Replace the optical bench with the one by Big Sky.

Lack of space makes it harder/impossible with the 2-part system. Louis
 

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Posted by Mark Gulbrandsen (Member # 72) on 06-17-2007, 10:24 AM:
 
MOnte...

Now's your big chance to shame them into buying the u.g. kits!

1. I did alot of the number 1's back in Chicago... alot of work for about 20% gain in light. Louis... why did my castings say Ringold Theater Equipment on the side and not Hadden Theater Supply? This kit is the cheapest of the bunch but does not offer enough improvement over other available options now available to warrant the labor/cost expended.

2. I've done alot of number 2's all over the place... this by my experience is the best option as long as you also get the new blower assy from Christie with the kit to properly pressurize the plenum. You will see unbelievable lamp life over any other upgrade option, so much so in fact that over 10 years the kit will pay for itself and you'll have triple the light output over the old mirror.

3. I've also done alot of these and its the only decent upgrade option for a Christie or Xetron lamphouse, results in at least two to 2.5 times the light output. With the smaller BS reflector the alignment is super critical if using a 3kw lamp in order to get the most efficiency, but you can if done carefully. One should use the USL light meter so you can see whats going on at many locations on the screen at once... makes install alot easier and quicker!! This is the second cheapest option.

The Christie plenum kit won't fit in their older lamphouse... note how much taller the present Christie lamphouse is. The RFS will however fit the old Christies and is priced about the same as a Christie Plenum kit. Standard lamps give even more output than the Christie kit and if you can use short gap lamps(as most drive in installs do) expect to end up with about twice the output of the Christie plenum kit .

Added: You can also install the Super-Lum-Ex mirror in the Eprad Universal if you remove the verticle center divider and enlarge the hole enough although today I would probably lean more towards putting in the Big Sky Mirror. You can also install the Kneisley Metal reflector in the 4000 watt Christie Lamphouse(Right Louis!).

Mark
 

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Posted by Monte L Fullmer (Member # 2797) on 06-17-2007, 03:58 PM:
 
Thx for the tips and suggestions on all of this.

This 4plex has one CH-20 and three CH-10 units. the "10" units are running CXL-10 bulbs that seems to keep their bulb life, yet this "20" as mentioned before, the bulb can barely go over warranty which we all know that there is something definitely wrong here since 2k bulbs can easily gather three times the life over warranty.

Now, I have to figure out how to 'sell' all of this to them by convincing them that they really need help, even though to them, all is okey.

You might say, I don't want to 'step on any toes' and presenting myself that I'm being judgemental on their operation and saying that the light output and bulb life is terrible where they think that it's just a normal form of operation..

...they are a touchy bunch over there and I have to walk on glass at times when I visit that 4plex...

-Monte
 

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Posted by Mark Gulbrandsen (Member # 72) on 06-17-2007, 05:25 PM:
 
All U have to do is convince them to do one of the consoles and when they see the results they WILL want to do the others . This works almost every time. Now these folks have to compete with the bug guys there in Boise so they'd better get their act together. You shouldn't have to walk on glass over there.... they should appreciate the fact that they don't hae to get someone form SLC or Portland to come there. You are saving them a ton... enough to do at least two of the kits a year. If they still make you walk on glass you should walk away. I won't service them and eventually they'd come back to you begging for service.

Mark
 

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Posted by Tristan Lane (Member # 1169) on 06-17-2007, 11:41 PM:
 
Monte, Now I know what site you are referring to!

I would push hard for those upgrades, or just get the owner to replace them all together. That theater is in dire need of upgrades, and will eventually fall to the big guy down the street if improvements aren't made.

Hell, there is that one Barco available that we were talking about..... Get the owner to put that in there.

But, I understand the "challenges" you have around there given the circumstances.
 

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Posted by Ken Lackner (Member # 1002) on 06-20-2007, 12:48 PM:
 

quote: Mark Gulbrandsen

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The thing about the heat mirrors as used in Strong's gear is that they just aim the reflected heat straight back at the end of the bulb.

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