# ERS reflector question



## derekleffew (Dec 18, 2012)

Seems like forever since we've had a QotD. Just because most are on winter break is no reason to suspend one's education. So a rather challenging, four-parter. Remember, students-only until January, when school resumes.

1. Why does this reflector, from an ERS, have two extra holes in it? 
2. Why is the hole for the lamp (presumably of the FEL-family) so large?



Here is the profile lantern in question:


3. What make/model is it? 
4. When was it made?


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## gafftapegreenia (Dec 18, 2012)

Pictures not showing.


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## derekleffew (Dec 18, 2012)

gafftapegreenia said:


> Pictures not showing.


Well that's going to make it even more challenging.

I'll get dvsDave on it.


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## techieman33 (Dec 18, 2012)

Pics show up for me.


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## Kurt (Dec 20, 2012)

well it is fairly far out of my league, but I can take a shot. Perhaps these holes are used as an escape for heat? I can't tell you about the make/model or year of the lantern but I know source four reflectors are made out of a special material designed to not reflect infrared light and send most of the heat out the back. Could these holes perhaps be a primitive form of the same design? (this also accounting for the large lamp hole). This would also account for the vent on the back of the instrument, that being a release for the heat. That's my best "educated" guess


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## Les (Dec 20, 2012)

Kurt said:


> I know source four reflectors are made out of a special material designed to not reflect infrared light and send most of the heat out the back. Could these holes perhaps be a primitive form of the same design?



Dichroic Reflectors. Also used in Altman Shakespeares, Strand SL's, and various copies. 

I'd say it's a good guess, but there were even older (and many newer) models out there that didn't have these holes, and also had aluminum reflectors.


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## MPowers (Dec 24, 2012)

Wow! This is a new one for me! I swear I've focused that unit.....when it was new. But I sure haven't seen one since! So I'll make a couple of guesses, 'cuz I'm as much of a student as anyone this time. 

1. The reflector's lamp hole is so large because it was designed for an incandescent, BBU lamp. Incandescent = before halogen, called quartz lamps in the period of this unit. The original lamp was probably a T-12 PF base or a T-14 MBP. 

2. The two extra holes were a design attempt to even out the field and balance out the lack of reflection from the lamp hole.?????

3. Brand???? Well, "not" Century or Kliegl. Not Electro Control(Arial Davis)

4. ??Mid 70's??


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## DuckJordan (Dec 24, 2012)

1. Why does this reflector, from an ERS, have two extra holes in it? 
For the original Lamp, The large hole carried the power while the other two held the lamp in place using a support system

2. Why is the hole for the lamp (presumably of the FEL-family) so large?
Because it wasn't for the FEL family it was for a larger lamp

3. What make/model is it? 
No clue whatso ever

4. When was it made?

It looks to be 73-74 ish era.


All these are guesstamations since I have no experience with these fixtures. I still consider myself a student even though I am no longer part of academia, Always need knowledge right?


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## LampyTom (Dec 29, 2012)

1) No idea!

2) Truthfully no idea but I would guess at because it was made to originally hold a larger lamp. (I know lots of the old strand kit was certainly this way before many of them got converted for T18/25 or T26/27).

3) Made by Strand Electric! Over here in the UK that green colour is VERY famous! There's still a LOT of old strand kit kicking around over here (heck Phantom in the west end still has Patt 123 and Patt 23 lanterns on it I believe). Most schools are still running old strand kit too - it just keeps on going! The Patt 743 fresnel I still maintain is one of the most beauitful fresnels of all time!

I would guess at a Patt 763/764.

4) 1971 - 1974.


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## derekleffew (Jan 1, 2013)

LampyTom said:


> ... 3) Made by Strand Electric! ... I would guess at a Patt 763/764. ...


Winner, winner, chicken dinner, LampyTom! I was hoping calling it a profile lantern would be a helpful hint to the Americans.

Strand Archive - Patt.763 / Patt.764

Patt.764 had bi-focal shutters; Patt.763 had only hard-edge shutters. I really will never understand how the Brits kept all those pattern numbers straight. Seems so un-intuitive.

From Patt. Lantern, Patt. Lantern, Patt. Lantern :

> *Patt. 763*
> Profile Spot, 1000W (GX9.5, T/9 Halogen) 20° max. dia deep
> facetted ellipsoidal reflector, four beam shaping shutters and twin 6 x 16-in. plano-convex lenses in (Century) diecast sliding, extending lens tube (secured by one screw!). Pressed steel lamphouse, hinged at gate area for lamp access.
> 
> Introduced 1971, replaced 1975 by T-spot 64.


This caught my attention as we were discussing Century lens tubes in this thread. It seems this is the first, and possibly only, time Strand Electric tried to work with recently purchased Century Lighting. One wonders why they didn't import the entire "LekoLite" fixture instead of just the tube.

As to the reflector question, I'm still baffled. But I have realized that the picture I posted above is upside down. (What is it with eBay sellers and non-lighting people that they always have stage lights pictured upside down?)



So the primary question remains: Why "extra" holes in the reflector? Didn't they realize back then that holes were a bad thing? Century had an axial ERS as early as 1969-1971, based on the EGJ lamp family, but only for their 8" and larger units it appears. I had originally thought the holes might be a holdover from an older design and intended for r7s double-ended socket, but that doesn't make sense as the filament would not be centered.

Anyone, anyone, Bueller?


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## MPowers (Jan 2, 2013)

I'm still guessing the added holes are an attempt to even out the field, much the same way as flatted and double flatted reflectors.


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## MPowers (Jan 3, 2013)

David North, Steve Terry, either of you guys know the answer on this one???


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## Kurt (Jan 4, 2013)

I went and googled for the answer. Nobody has gotten it right yet, but I would feel it cheating to post an answer I didn't know off the top of my head


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## derekleffew (Jan 4, 2013)

What on earth terms did you enter into Google?

Last chance before I sic the Strandinavians on it.

Another view of the reflector; right way 'round this time.


.


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## DavidNorth (Jan 4, 2013)

MPowers said:


> David North, Steve Terry, either of you guys know the answer on this one???



I don't know but have always wondered....cooling or lamp clearance are my only guesses. Bring on the ones who really know!!

David


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## Kurt (Jan 4, 2013)

derekleffew said:


> What on earth terms did you enter into Google?
> 
> Last chance before I sic the Strandinavians on it.
> .



I just googled ERS reflector with holes in it. Didn't get that exactly in the response but I found a page that gave a brief explanation of the hole. I say go ahead and sic the strandinavians on it, they will give a much better explanation


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## Les (Jan 4, 2013)

Kurt said:


> I just googled ERS reflector with holes in it. Didn't get that exactly in the response but I found a page that gave a brief explanation of the hole. I say go ahead and sic the strandinavians on it, they will give a much better explanation



Can you provide us with a link? It _is_ January, after all.


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## SteveB (Jan 4, 2013)

I'm going to take a stab that possibly the holes were for support structure for a other-then-incandescent-lamp ?.

Possibly this particular fixture was for an architectural application ? and not a reflector used by a an incandescent lamp ?. 

I'm going to copy the image and see if I can post it over on BlueRoom, the British stagecraft forum. maybe some old timer on the other side of the pond would enlighten us (a pun)


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## STEVETERRY (Jan 4, 2013)

I have looked at this, and scratched my head, since the question was posed, and quite honestly, I have no f***ing idea what those extra holes are for. I don't buy the idea of evening the field. I suspect an arc-source lamp, but I have not heard of that as an option in the Strand 763.

Sorry to disappoint!

ST


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## erosing (Jan 4, 2013)

Chromatic aberration?


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## ship (Jan 4, 2013)

Doesn't seem as if the photos were on a new reflector and delivered from the factory that way, but instead something found on-site and already installed into a fixture. If the case, no doubt what better way to vent a fixture than destroy the optics of it by way of drilling holes in the reflector for venting? Perhaps a moot point in asking - something seen, something somebody did and something one should not be doing if one really understands the fixture? Perhaps these were 1Kw lamped fixtures that were burning thru sockets and it was an amature idea on how best to improve the venting on them so as to preserve the incorrect lamp running too hot for the fixture.

Interesting, not seen this before but have seen the old style TP-22 socket drilled and tapped and fitted with a thumb screw so as to retain the lamp better - no doubt during the same era of 1Kw FEL lamps needed to be used. And yes, both "upgrades' do date back to the Super Reflector days.

If the case that this is the "new" super reflector, please confirm this info and I will contact my sources at Altman and get the answer.

On the other hand, in re-viewing the second photo for the "lantern" in question, what brand is it? I don't know what it is either. Above concept in drilling holes in a reflecor for cooling probably still apply.


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## Kurt (Jan 5, 2013)

Les said:


> Can you provide us with a link? It _is_ January, after all.



Sure thing. http://www.personal.psu.edu/bsk5023/blogs/briank_engl202c/How an ERS Works.pdf
Under the "ERS: A Brief History" heading, third paragraph down explains the holes.


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## techieman33 (Jan 5, 2013)

Kurt said:


> Sure thing. http://www.personal.psu.edu/bsk5023/blogs/briank_engl202c/How an ERS Works.pdf
> Under the "ERS: A Brief History" heading, third paragraph down explains the holes.



I didn't see a reason for the extra holes in that link. There was also a lot more bad info in there. They must have super tough hands too if they think you can touch a 100 watt incandescent bulb after being on for hours without burning yourself too.


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## Kurt (Jan 5, 2013)

techieman33 said:


> I didn't see a reason for the extra holes in that link. There was also a lot more bad info in there. They must have super tough hands too if they think you can touch a 100 watt incandescent bulb after being on for hours without burning yourself too.



it said the holes were a solution to the lamp itself casting a shadow, which was solved by making reflectors with a lamp mounted straight in


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## techieman33 (Jan 5, 2013)

> The Radial had the lamp mounted at an angle which meant that the lamp
> actually cast a shadow in the beam. While not noticeable in normal use, it
> also put a hole in the side of the reflector, leading to less than optimum
> light output. The Axial fixed this problem by having the lamp mounted
> ...



This paragraph doesn't explain multiple holes. It says the older non axial fixtures had a shadow from the lamp due to the hole in the side of the reflector where the lamp was. Then that that problem wasn't an issue anymore when they introduced the axial fixtures since the hole was in the center of the reflector, and not the side. It may be possible that the holes somehow helped with a shadow problem but this document does nothing to give us an answer one way or the other.


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## Les (Jan 5, 2013)

techieman33 is correct; this article is more a description of the large elongated hole for the actual lamp. I will also agree that there is a bit of misinformation sprinkled about -- I wouldn't necessarily say that both types of fixtures "require a lot of maintenance to keep running". Keep your bench focus as optimum as possible, change the lamp socket every decade or so (in heavy use), and maybe replace a shutter blade here or there... That's really about it. 

Just a bit of trivia for the younger guys: To follow up on what was left out of the article above, the reason for the non-axial lamp was because the huge incandescent lamps had to be burned as close to base-up as possible. I've heard a few reasons for this, and they're probably all somewhat correct. One being that the filament supports would fail when turned at an extreme angle, and another suggesting that since there was no halogen cycle, the black deposits from the filament could gather near the lamp base rather than on the globe where it would more interfere with the output.


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## JohnD (Jan 5, 2013)

To add to what Les said about BBU lamps, I understand that since it is a lensed fixture, the beam is inverted and since the hole for the lamp causes dark areas of the beam, it is better to have the dark areas fall on the floor rather than on the face. Another pre-Halogen cycle bit of trivia, many lamps had (I think) granules of sand in the bulb so you could shake the lamps like maracas to remove some of the black buildup and extend the life of the lamp.


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## LampyTom (Jan 5, 2013)

See I've just heard something else from someone I know. Mr Jim Laws - Strand expert in the UK and has loads of strand (and other older) lighting kit. Including a Light Organ from Drury Lane Theatre! He said the two holes at the back were for ventilation and the lamp sits base down in the 763/764 range.


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## derekleffew (Jan 5, 2013)

Thanks for pursuing the topic, LampyTom. I wonder why no other fixture had to resort to extra holes in the reflector for cooling. Was this the first, or only, ERS from Strand that used a BBD design? With the BBU lamp used in radial units, the heat escapes around the socket, keeping the pinch seal temperature to a reasonable level, but over-heating the socket. Lighting manufacturers didn't yet understand all the rules of convection currents and thermodynamics.

Looking through my notes, I found a post to the Usenet group: rec.arts.theatre.stagecraft, by Martin Moore, buried on my hard drive since 1999. Sadly, it doesn't mention the extra holes. But it does contain great historical information from an inside source. I knew Mr. Moore when he worked for Kliegl Bros. in the 1980s.

> for any history buffs out there
> 
> T-spot was the marketing take on the internal (derogatory) R&D name --
> tin-spot
> ...



*Arez* -Chromatic aberration is a function of the lens(es), not the reflector.

JohnD -You're correct about older,larger incandescent lamps having sand or granules in them so the user could remove the blackening of tungsten deposits. But this only worked with BBD lamps, and as one could imagine, proved a maintenance nightmare. "Whose turn is it to remove and shake the lamps this week?"

Kurt -The document you found appears to me to be a high school or college term paper on the ellipsoidal reflector spotlight. Not exactly an authoritative source, and it doesn't address the multiple hole issue.
.


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## Kurt (Jan 5, 2013)

but I was onto something with the heat release! "A" for effort?


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## JChenault (Jan 6, 2013)

Les said:


> techieman33
> 
> Just a bit of trivia for the younger guys: To follow up on what was left out of the article above, the reason for the non-axial lamp was because the huge incandescent lamps had to be burned as close to base-up as possible. I've heard a few reasons for this, and they're probably all somewhat correct. One being that the filament supports would fail when turned at an extreme angle, and another suggesting that since there was no halogen cycle, the black deposits from the filament could gather near the lamp base rather than on the globe where it would more interfere with the output.



My understanding is that it had to do with how to reduce the heat from the filament on the glass bulb. "In the day" a burn base down lamp was typically a G lamp (Globular). Using this kind of lamp in a Leko would have meant a large hole in the reflector. So they designed it using a T (Tubular) lamp. If you burned the T lamp horizontally the heat from the filament would rise and soften the glass bulb. If you burned it base up, the heat had time to spread out a bit. I have vague memories of sometimes replacing T lamps that the bulb had started to blister on when burned in an improper position.


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## derekleffew (Jan 6, 2013)

JChenault said:


> ... I have vague memories of sometimes replacing T lamps that the bulb had started to blister on when burned in an improper position.


"Blister" is a bit of an understatement. We called them "pregnant lamps." The bulbous, phallic shapes to which even the 750T12/9 could deform made them downright obscene. When it could no longer fit through the hole in the reflector, the only way to remove the lamp was to open the fixture at the gate. In very rare cases, one had to actually break the envelope in order to remove the lamp.

Kurt -Sure, what the heck; "A" for effort.
.


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## Les (Jan 6, 2013)

So, about the huge hole to accommodate the lamp... 

In the BBU era of ellipsoidals, was it all just a matter of convenience so you were able to re-lamp from the rear of the instrument? From my understanding, the lamp bases (the actual part of the lamp) were never really any larger than a medium prefocus. They wouldn't have been able to counter _all_ of the issues associated with an off-set hole, but it seems as though they would have counteracted some of them by simply designing the fixtures to be re-lamped from the front (many ellipsoidals - like the 360Q - have a hinge at the gate) and having a smaller hole in the reflector since only the base had to fit through and not the entire bulb portion of the lamp.


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## derekleffew (Jan 6, 2013)

The hole in the reflector has to be just a little larger than the lamp's envelope. T12 and T14 lamps were common in 6" units; some cannon Lekos could take up to a 3000W T32--huge hole! At the time, no one made "long neck" PS shaped bulbs for stage fixtures. I'm sure there might have been some ERS units that only lamped from the front--the only one I can think of at the moment is the Kliegl Bros. 1357 series which used a double-ended lamp.


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## Kurt (Jan 6, 2013)

Les said:


> Just a bit of trivia for the younger guys: To follow up on what was left out of the article above, the reason for the non-axial lamp was because the huge incandescent lamps had to be burned as close to base-up as possible. I've heard a few reasons for this, and they're probably all somewhat correct. One being that the filament supports would fail when turned at an extreme angle, and another suggesting that since there was no halogen cycle, the black deposits from the filament could gather near the lamp base rather than on the globe where it would more interfere with the output.



I found this: http://www.geappliances.com/email/lighting/specifier/2008_07/downloads/HIDBurnOrientation.pdf

The article does some discussion on minor color variance in lamps depending on how they are oriented, as well as how long the lamp has been burned for. Is this possibly another reason for the lamps being burned base up?


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## Les (Jan 6, 2013)

Kurt said:


> I found this: http://www.geappliances.com/email/lighting/specifier/2008_07/downloads/HIDBurnOrientation.pdf
> 
> The article does some discussion on minor color variance in lamps depending on how they are oriented, as well as how long the lamp has been burned for. Is this possibly another reason for the lamps being burned base up?



That article discusses HID (High Intensity Discharge) lamps which don't play by the same set of rules that quartz-halogen/incandescent lamps do. I'll see if there's any direct correlation when I finish the article, but I'm thinking not.

Update: Yeah, that article is referring to a family of arc lamps (metal halide) which use processes and gasses to create light non-existent in incandescent lighting. Think "gymnasium lighting". 

Here's a couple of diagrams showing the differences between each:

Metal Halide:



Incandescent:

Though this is just the diagram for a normal household lamp, it isn't terribly different than the incandescent lamps being discussed here (for illustrative purposes, at least).


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