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Topic: Removal of lamp filters in Elmos....

Greg Marshall
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From: Nashville, TN USA
Registered: Sep 2008

posted June 16, 2009 09:50 PM

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I've been disappointed in the amount of light that my ST1200 allows. I remembered removing the filter that is installed in the machine I had back in the '90's, and did so again with the one I have now, and wow, does it make a difference!

Can anyone shed light (no pun) on this subject? I'm sure the manufacturer put that filter in there for a reason. But, I am not noticing any damage to film passing through the gate, so I'm pretty pleased. Comments?

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Dino Everette
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posted June 17, 2009 02:31 AM

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Isn't that used as a backup for the drop shield when you are turning the switches forward and reverse, etc. Plus my guess would be that it helps absorb some of the heat of the lamp on the gate....I actually have one of mine where I don't have the whole lamp cover and I have run many films through it and haven't noticed any damage...I think you are OK, especially if it is helping with your light out put.

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Gary Crawford
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posted June 17, 2009 08:19 AM

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I was on the phone last night with U.S. Elmo expert, Leon Norris...and he told me that he has never figured out what that glass was supposed to do, but whenever he gets a machine for repair, he , with the owners permission, removes that glass...and it adds a discernable amout of light to the screen. He said he had talked with someone who used to work at Elmo and he said he never knew why it was there , either.

I've taken them off my st1200's...with no ill effects.

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Mark Todd
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posted June 17, 2009 08:54 AM

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Elmo`s unlike many super 8 machines fan over, and onto the bulb and very well so if the glass is in, whip it out.
Its no worries at all.

Best Mark.

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Joe Taffis
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posted June 17, 2009 04:00 PM

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using the 'search' feature here on the forum, type in "elmo light output". Lots of stuff on this topic from long ago. [Smile]

[Smile]

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Joe Taffis

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Dino Everette
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posted June 17, 2009 04:48 PM

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Thanks Joe, and I actually used my newest elmo (sans glass) to screen some very rare one of a kind sound home movie footage of slain politician Harvey Milk last week for a crowd of about 50 people, so it is safe to say she is up n running great, and I ran the audio out through an amp and it sound really great...Now I just need to get an optical print to check out the sound on that one...

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Greg Marshall
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posted June 17, 2009 09:17 PM

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Thanks for all the replys, guys... I feel much better now. The amount of light is significantly better than with that glass in tact. I'm even ready for Scope now. Well, if I had a lens... ha.

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frank arnstein
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posted July 24, 2009 11:20 PM

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Hi Greg & others on this thread.

With regards to the Glass piece that is removed by many......
I have a hypothesis as to its true function....

The fan delivers pressurised cooling air to the lamp which flows past the lamp and exits somewhere and dumps the hot air outside.
If there was no glass piece in place, pressurised cooling air would leak out from the hole left by removing the glass. The glass is actually part of the ducting system for the lamp cooling air & to remove the glass is like putting a big hole into your pressurised cooling duct. This will substantially alter the ability of the lamp cooling system & hot air will also leak out directly onto the inside of the gate & aperture. This will heat up the gate and possibly damage film that is in the direct area especially a frame in the aperture.

So thats my theory of why they use the glass plate in the 1st place.
Projected light easily gets through the glass but not air.
Some of these glass plates appear to be cracked in half but thats how they are made. The line is to allow for expansion in the glass. It would soon crack from heat without the expansion join.

What do others reckon about this theory?

dogtor pufferfish

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[Roll Eyes]

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Greg Marshall
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posted July 26, 2009 10:30 PM

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Thanks, and that does make sense, however I wish the company would have used a clear tempered glass instead of the milky, opaque-type.... the amount of light loss because of that is significant, enough for me to keep the glass out. Now, because of my decision, I always turn my lamp off before shutting down, and rarely stop a film during projection.

Any other thoughts? Anyone, anyone, Bueller, Bueller?

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Graham Ritchie
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posted July 27, 2009 05:29 AM

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Frank is spot on, I have said the same in a previous post in the past. That hot air has to be blown out the top, not having some of it heading towards your gate and films, The last thing you want in a projector is a lot of hot air blowing all around the place. The best bet is to get some more heat resistant glass made to fit.

Graham.

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Gary Crawford
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posted July 27, 2009 09:33 AM

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My experience has been that st1200 light can be boosted a lot by 1. getting that glass filter out of there 2. buying osram xenophot lamps...these things give out a lot more light than other 150 watters. 3. find and invest in an elmo f1.1 or , even better, an elmo f1.0 lens. they really allow more light onto the screen. I found that those improvements brought brightness almost up to what I was getting from an elmo GS with 200 watt bulb and three blade shutter.

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Joe Taffis
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posted July 27, 2009 04:13 PM

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hi all, Greg, you say your glass is "milky/opaque". Here is a pic of one of mine I just popped out for this pic...it's from an ST1200D mag/opt, and it is perfectly clear...so I leave it in the lamp housing. [Confused]

[Confused]

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Joe Taffis

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Greg Marshall
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posted July 27, 2009 07:10 PM

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Guys, thanks for the posts.

Gary, I have installed the Osram Xenophot lamp, am currently leaving the filter out... and have been looking for a 1.1, as mine is the 1.3. One day, I'll run across one, reasonable.

Joe, that is not like the glass that I removed from mine. My unit is a ST1200HD mag/opt, and the glass I removed from mine is a light greenish/milky-greenish/opaque piece of glass... it does have the expansion crack, but you certainly cannot see through it... so you can imagine how much light is not allowed through. Yours is clear, with the expansion crack. Did you replace it with that, or did yours come with it?

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Dan Lail
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posted July 27, 2009 07:51 PM

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Well I just removed my lamp filter and can se more brightness in the picture. Thanks.

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frank arnstein
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posted July 28, 2009 12:58 AM

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Hi again to all on this interesting Elmo thread.

I believe that all these Elmo hardened glass "windows" were originally clear & fully transparent.
Due to the intense heat that the glass is exposed to & repeatedly over many years, the glass may change its chemical composition & it turns opaque. We could think of the glass as "burnt" & it should be replaced, not just removed & then left out.
Imagine the total amount of heat that is blown onto the aperture & gate area after half an hour of projecting a 150w Halogen lamp?
I would think it could "cook" whatever frames are in the gate or near the aperture, especially if you stop for a minute during the film near the end.
It's interesting to try & visualise the flow & movement of heat through the parts of a projector. We can't see the heat but its there every time we run our projectors & it must be disposed of in the most efficient way possible or we will have a film BBQ that we don't really want.

dogtor pufferfish

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[ July 28, 2009, 07:19 AM: Message edited by: frank arnstein ]

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Paul Adsett
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posted July 28, 2009 12:48 PM

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So how come the GS1200 does not have one of these fixed filter glasses? I would have thought that if Elmo decided it was necessary to have this glass on the 150 Watt ST1200 that they would also have put one in the 200 watt GS1200.

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Greg Marshall
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posted July 28, 2009 02:18 PM

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I don't own a GS (yet).... they don't have any type of glass filter like the ST's?

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Paul Adsett
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posted July 28, 2009 03:46 PM

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No, there is no glass filter on the GS. When you go to still frame, a solenoid is activated and drops down a glass filter and perforated metal plate behind the gate, but it is lifted out of the way for normal projection.

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The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
Elmo GS1200 f1.0 2-blade
Eumig S938 Stereo f1.0 Ektar
Panasonic PT-AE4000U digital pj

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Greg Marshall
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posted July 28, 2009 05:59 PM

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From what I've read, I'm thinking it's the same type of filter that drops down in the GS, that's permanately in the ST.

And, Paul, BTW, whenever you want to sell your scope Grease print, please let me know.

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David Kilderry
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posted July 28, 2009 11:27 PM

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Many 35mm xenon lamphouses have glsss heat filters, both split and solid, but not all of them. Some manufactureres deemed them necessary and others did not. It does not seem to correlate to the size of the xenon either.

We run our 5,000 watt xenons without a filter (Strong X60C, D and Super 80 lamphouses) and the heat on the film is much higher than any non-xenon Super 8 projector could ever generate. We don't have problems with scorch, buckle or warp either.

I am certainly going to check mine in the ST 1200 now.....

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Greg Marshall
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posted July 29, 2009 12:02 AM

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The old Eprad xenon lamphouses I used to work with had the split, heat glass in them. The Christie lamphouses I have worked with did not... the Christies were 2000, 3000, and 6000 watt units, and we never had a problem with blistering, etc., as well. The gates got hot, especially with the 6000's, but we never had any problems.

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Dino Everette
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posted July 29, 2009 01:20 AM

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I used to take the lamphouse off before realizing it was easy to remove the glass. So much so that I have misplaced the lamphouse for my mag only ST [Frown]

[Frown]

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David Kilderry
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posted July 09, 2010 10:01 PM

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Have any of you who may have removed your ST 1200 glass filter noticed any shortening of lamp life since you did it?

I am satisfied that no damage will occur to the film through increased heat, I just wonder about lamp cooling and its affect on lamp life.

David

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Rob Young.
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posted July 10, 2010 07:00 AM

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Just to second the point, but the glass is totally clear on my 30 year old ST1200HD.

Think if it is opaque, something's definately gone wrong with it.

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Greg Marshall
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posted July 10, 2010 10:08 AM

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David.... I really haven't noticed if I'm replacing the lamp more often or not.... it's a non-issue to me, as I'd certainly rather have the increased amount of light anyway.

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