light design and instrument selection


Hi there...

Basic theory question for anyone who knows/remembers. I'm trying to spec some new instruments and repair some old ones (mostly 360q's), and what we have (all donated instruments), are way too short of a throw for our space, from any position, it seems.

IIRC from my stagecraft class, many long years ago, and from my own experience and preferences...please check me if I'm wrong...or right...

The best instrument to choose to light an area onstage from a given position (instrument = ellipsoidal) is one that will produce a 10 foot circle of light, i.e. a 10 foot beam angle, for that particular throw.

Am I remembering that right? Seems like I am. Right now I'm working with 6x9's and 6x12's mostly. The 6x12's, from our most rear-of-house position (plaster line-plus-50-feet), put out circles big enough to light the whole proscenium, the floor, the ceiling, etc. I have the shutters almost completely closed off and the instruments up no more than half to 75% (575w lamps). Seems like a waste of instruments, doesn't it?

10' beam angle is optimum, right?


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The 10ft rule is just a guidline. With that size you should be able to get two actors into the space to do a scene. I think it was found that size was a good one for dividing the stage up into areas.

How many FOH bars do you have and why do you need to use the rear bar for the 6' x 12'. The closer to the stage the smaller the area, also the brighter. The time I would use them that far back would be to give a front of stage colour wash.

Personally I prefer using adjustable degree lights because they give more flexibility in design then fixed. I am just hanging a rig for a community theatre at the moment. They have some new fixed length Strand SL's which are bright. The trouble is because the show is a 1930's musical we are only using general washes with fresnel's. The strands are being used for specials, also for sidelighting. Being fixed means that in different positions the lights give different size areas. If I was using adjustables I would be able to make the area sizes more consistent and/or more fitting to the job. Eg smaller area for a soloist.

So when you are spec'ing new gear I would at least get some adjustable size lights in for a trial. They might cost more but make up for it in flexibility. If your donated lights are working I wouldn't throw them out as "every light will have it's day". The only time I would look at no longer using lights are when their performance is poor and if you have to keep a special bulb in stock for that one light alone.


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"Photometrics Handbook" by Mumm is very useful for looking at the intensity, beam dia. and foot candles of any type of fixture given a throw distance. Unfortunately they don't do more modern lamps if not initially secified for the fixture, but they do give the formula for converting it to a different lamp which you can write in after doing the math. This is a must buy for anyone doing the math in design or choosing fixtures in general. All lighting tech people should own one of this book and a "Backstage Handbook" at very least.

Otherwise for further info on doing design in this way of the math, Stage Ligthing Handbook by Reid goes more into the calculation formula for design by the math - this even if written for a UK audience and unless a newer edition is out, dated. Ried I believe presents the concept for this design style best. Such was the system about 20 years ago I learned lighting design by way of in following the numbers. - At least right before Gillette's Designing with Light and better classes in lighting design where it got less into the math and more into the design concept details availed themselves to me back than. OR perhaps I was more ready to understand the concepts a second time around with a second and third class in lighting design. Nothing wrong with also doing the math in design and it would help, just more to it than that and both theories supplement each other. These books especially supplemented by Rosenthals The Magic of Light which was a bit over my head at the time but later proved very useful as a concept for design on to itself. That's the second best book on design ever written - even if only "A method". "A Method" which reminds me of "A Method of Lighting the Stage" by McCandless amongst his three other books. (Anyone name them much less why they are also important books?)

Not "the method" people fight against in finding their own style or constantly saying how much they strive against it, but "a" primary concept once understood in, theory and method presented in the primary book on lighting design for the industry. Jean Rosenthal was a student of his at Yale as were many pivital designers to follow. No other book on theater tech has had as many re-printings or as much influence.

After that at least for me, I still pick up "The New Handbook of Stage Lighting Graphics" by Warfel and "Handbook of Stage LIghting Graphics" also by Warfel to get the paperwork done.

Myself, while I can do it by the math of foot candles while in front of my drafting table, it's more by way of experience what to put where. At X distance, this this focal length fixture will give me a desired intensity and in this dia. for the most part. If designing with gear I'm less than experienced with, than doing the math and comparing it to what I do know at the same distance and angle would accurately save the day in design by way of converting one to another. If used to say Radial Century 6x9's, much less S-4 fixtures, and faced with Color Tran Mini-Ellipses, there would be a huge hump to get over otherwise in doing the design without doing the math.

From memory in even hallway lighting intensities, 10fc seems very low. A single 150w R-40 flood lamp at 10' produces that amount. (not much punch to this amount of fc. Might be okay for a night scene and only once the audience's eyes are adjusted, but it's as a concept probably a bit low for most uses. Good not to blind one's audience with a few hundred foot candles, but also good to not leave the stage in the dark.

The 6x12 at 50' produces a 23' beam at 61 foot candles. Imagine that intensity and beam spread and how dim it is, than by way of foot candle number consider that of FC amount as something to improve upon.

At 50' you would be better served by a 6x22 leko or something in the range of 10 degree Leko. Any of which should give you something in the range of 80 to 275 foot candles with a 9' beam. All dependant upon fixture and lamp type.

A few 6x22 or 10 degree Lekos would be correct in your estimation. But that's front fill only and not very directional. A few (say up to eight on a 30' main stage) to wash the apron stage where needed, than probably lots more in the 25' distance in the 6x16 or 26 degree range would be much more useful in front light in continuing the lighting design at less flat and from the front angles of wash. For a theater's FOH, the 50' mark is for the wash more than anything else, the 1st or better yet 2nd house electric if at about 25' is much more useful. 1st Electric if less than 25' and normally near the slightly thrust stage apron is a very useful position for 6x12 and 6x16 fixtures for beyond the apron on stage proper lighting or effects to the stage.

For the 6x16 at least, that's an easy trade if you have extra 6x12 and 6x9 lens trains. These are the more valuable lens train types. Most frequently you will find theaters with too many 6x16 types looking for a few more instruments they can use on stage.

If nothing else, drop me a line off line and I would probably be willing to trade a few months from now once I un-pack them some of my pallet full of haven't been used in 15 years Altman lens trains much less extra lenses primarially in the 6x16 type for some 6x12 or 6x9 that are much more valuable in short throw situations such as would be useful for my primary small theater customers. Just climbed to the top of the rack about a week ago to bring down a 6x9 lens train in resale. That it was 6x9 in tube and barrel only it had 6x16 lenses installed in it and I was not up for another climb up top the rack. Boxes full of 6x16 lenses much less complete 6x16 lens train assemblies, very few other stuff. Might even have a few and up to two 6x22 lens trains left but I won't know for a few months. Unpacking that pallet is a long term project for me along with the pallet of 6-30 and various forms of 360 and 360Q fixtures rusted solid, full of smoke goo and trashed I will get to some day. Easy resale but not enough time in the day to fix them and get shop stuff done. Instead these fixtures are my carrot on a stick in some day having the time to play with.


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Further notes, it's easy to trade off a lens train in keeping the rest of the pineapple of a fixture you know than in getting a whole new fixture that will have someone else's standards for care. Holes on the barrel might not line up, but that's easy to fix. Dependant upon your fixtures, you might also have to install a second clutch cam especially for a 6x22. If that's the case and if not easy to install old style but easily broken, than swapping the entire fixture would probably be good.

That's trading lens trains. Don't know if it's possible to E-Bay a trade in kind but if it's possible, that's where I would attempt to do the trade. Perhaps you list your lens trains for a buck in resale when in trade for something you need. Otherwise if you do a search on this website for "used" gear, you will find other sources that provide either free or for a cost retail of gear services. Intent is to keep the actual retail off line or off the website but not be against advice on it.

In buying more or used fixtures, $110.00 for a 360Q would be my top for a used one and that price only if coming from a repuitable dealer. The 6x22 might be worth say $20.00 more only given they would be more limited in availability. There is two types of 360Q, one with the aluminum clutch cam and the other with the more modern break assembly. Judge your value upon also this as the older type while easy to install is also easy to break.

In serviceing your fixtures, you mention 575w lamps but not the specific type. One easy improvement to output is tossing in the trash any HX-600/FLK lamps or HX-601/FLK-LL long life lamps if in use. Instead go Phillips GLA for long life and best overall output (recommended) or GLC for high output though less recommended unless doing high output needed shows over that of normal operating cost shows. Otherwise the Osram HPR 575/115 lamp while less good for pattern projection than a GLC probably is a much better lamp for high output use. This especially in theaters that don't really have time to do a serious bench focus of the lights. With the HPR, a bad bench focus doesn't really matter, it will still in a 360Q probably out punch and out flat field even a S-4 fixture. This even when out of bench focus. In playing further with this lamp, it was very hard to throw a fixture with it out of a flat field. Good type of lamp where less skilled labor in installing or caring for them is involved but given it's only a improved HX-600/FLK with internal reflector, while easier on the accuracy still has a fairly large and less than premium point source in filament. Darned good lamp but only rated for 300hrs at 115v thus unless one has the budge for replacement lamps as simliar to that of a HPL 575/115v WC or high output lamp, it's not worth the 300 hour lamp life at 115v. A probalby any brand of GLC in having similar much smaller filament is a better lamp overall for the 360Q or any similar fixture. The GLA otherwise is the best cost efficient 575w lamp for a 360Q or any fixture on the market in my opinion in at 115v being rated for 1500hrs. Somewhat difficult to tell the difference between it and a EHG 750w/120v lamp last time I sent it out for play testing.

For a 6x22 on the other hand given it's throw distance, I might go with a Phillips #6981P for high output/shorter life or better yet for life GE/Thorn GLE for long life in providing a bit more light to compensate for the (law of squares) throw distance.

After this is reflectors and lenses. Dependant upon what era of 360Q you have, you might still have green lenses. Easy to tell by way of looking at them once removed. If green or amber in looking at them, they are green. This as opposed to very clear or blue in look you will specifically note. The price of replacement lenses is not cheap but you could do them on-line to some of the more major lighting production companies that still have extra lenses in stock many years after they converted to S-4. I know I have boxes of 360Q lenses both blue and green.

Next is reflectors - in doing your 575w lamps, be careful even if bench focused of the reflector no matter which of now three generations of reflector you have unless the reflectors have been bought within say the last two years. The old reflectors even if upgraded and honeycomb sectioned type in still only having a 7/8" dia hole are not as well designed for taking a T-6 lamp (3/4" dia) as that of the most modern reflector in having a 1.1/4" hole for the lamp.

Bought some 1KAL 6-30 reflectors probably two years ago and never installed them. Recently bought for a customer some of the same and ran short. I compared the upgraded honeycomb or more recent designs and found a primary difference in hole for lamp size between the two reflectors. This in addition to actual ellipsoidal shape of the reflector now being different no doubt in part to compensate for the larger hole. Lots of discontinued reflectors in the altman line and especially gate reflectors, but they if similar are in many ways univesal. I will if requested go further into both my and the customer's play testing of not the right reflector but similar examples of working sufficiently. For the most part, I believe that there is three versions now for the 360Q reflector. Old style that's coincentric, first upgrade that's more rectangular in honeycomb and a I theorize one similar but with a larger hole and I expect slightly different shape. Yet if by memory to see the most recent 360Q reflector but it's probably similar to that of the 1KAL I have seen recently.

This all makes sense and given the T-6 lamp is of value. Larger lamps more easily bottom out against the reflector if not for a larger hole. I know that in my own bench focus of some HPR lamps in some 3.5Q fixtures I did destroy a lamp by way of bench focus when the lamp bottomed out against the reflector. For T-6 lamps in Lekos, a change in bench focus policy is probably necessary otherwise for the older reflectors. First open up the fixture in half and adjust the lamp so it seems centered on the reflector. 1/16" between lamp and reflector edge all around should be easy enough to adjust for. Than close it up and bench focus for distance of lamp in height. Bank on the lamp closer to the lamp base as opposed to the reverse of this in most cases. Count the number of turns of adjustment and apply it similar to all sides in a general focus, otherwise don't exceed 10 half turns in going to one side or another. If one in bench focus needs to go beyond ten turns in homing in one one side after the initial viewed center in the reflector do two things. First ensure the cap is screwed tight and lamp seated, than re-open the fixture to ensure the lamp is again centered on the reflector. If still centered, continue once seen to need to go more to one side the adjustment. Once found into some semblence of bench focus, re-open the fixture and examine how close that lamp is to the reflector and re-adjust or configure as needed. Lamps too close to the reflector especially if touching it is a bad thing such notes in bench focus are to prevent. Close the fixture up again an re-bench focus. Hopefully it's good now and even if radial Leko, a fairly flat field.

Beyond this is reflectors themselves. Amazing what milky reflectors in replacement will do for output, this much less what gate reflectors where replaced when also bad will do for the instance. Gate reflectors are also often discontinued but in geneal and especially no matter the brand or age similar. At times you even if different mounting style can sleeved a craped up but different mounting style reflector with a new one. Key is to have good reflectors, this much less not green lenses. That's an output boost.
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Wow... Just read Ship's reply. Ship, I'll get back to you on that--I think we might be able to do something.

The house I've got...for what it is (a former community center/rental hall/soroptimist's club)... 45'wide by 86' long, 13' of that length being the depth of the stage, which is +30" elevated from the highly-polished VCT floor. Three large rafters in the hall angled up in the center from 12'tall at the walls to 16'tall in the center, two 10' sections of pipe bolted to each rafter, from 2' either side of center on down. Proscenium is 10'tall by 22'10" wide (translation: almost any position I shoot from is a dead-on in-the-face shot to the folks on stage.

We seldom use the stage by itself, in favor of a rearrangable group of platforms as a thrust (usually 16 feet out and 32 feet SL to SR) , occasionally using floor level as well (as we are now for Schoolhouse Rock Live! Jr.) My positions are approx. 10' from the plasterline (mainly fresnels for downlight and effects), 31' from the plasterline (right now a mix of 6x9 360's and 360q's, plus some I can't identify, 'cept for knowing they're very old and painted grey and have "CENTURY" stamped in the yoke handles, plus 2 36deg S-4's) and 53' from the plasterline (six personally bench-focused and cleaned and identified (by pulling the lenses and measuring in sunlight) 6x12 360q's)

Right now (until our new Express 24/48 comes in, plus two new dimmer packs) my system consists of a Leprecon 624 board and five boom-mount six-dimmer dmx packs, one on 53', 2 on 31', 1 on 10' and 1 behind the proscenium for backlight and effects. We've got fresnels out the wazoo, more 360's and more Century ERS's (oh, yeah, our fadeable houselights are four scoops aimed up bouncing down off the white ceiling, run to a Home-Depot two-dimmer arrangement, the less said about which the better.) ALL of our gear thusfar was donated from other theatres doing upgrades or junking their surplus. Most of the fixtures end up left hung where they were by the last LD/ME who had initiative put them and are simply reaimed a bit, and all are in dire need of cleaning/repair, which I simply haven't had time to do because usually I end up doing lights, set, sound, setting up the house (up to 200 seats, depending on the configuration we want), buffing the floor, patching the holes in the roof, fixing the gutters...oh, wait...that was just today's worklist. *sigh*

We do do good things, neat effects with what we have... one I'm particularly proud of--we did Stalag 17 a few months ago, and decided we wanted a searchlight effect, and it was called for in the script at the end as well, to shine in the barracks. Mounted a 2' section of pipe on the back wall of the stage up high, borrowed a pneumatic actuator arm and the tank and hoses to operate it ran back to the tech table, mounted that to the pipe and mounted one of our S-4's to the arm, and ran it with the backstage dimmer pack. Barracks lights would go out, S-4 up to full, move the arm controller, swing the light all the way across the stage, fade it out, swing it back, up, swing, down again...looked flippin' sweet. Especially at the end of the play, when I aimed it and the other S-4 mounted next to it at these rickety z-frame doors I cobbled together from the upstage side, no other lights on, and then the gunshot sound effects went off and the crew pulled the bullet-hole effects I'd drilled into the door... very convincing gasp-inducing machine-gun strafe from a guard tower. Every night someone would gasp and I'd be in back pumping my fist in victory and pride.

...I guess it's little moments like that that make it worth it sometimes.

Oh, if you want to see a very rough plan of our space, .
Good grief but I've got a lot of work to do...



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Sounds like you made art at one point, that’s why we all attempt such things. This especially no matter what life deals us in paint brush.

Century lekos, 360's and 360Q’s have in recent years become sort of my pet project. Where I work it’s all S-4 with the Altman gear should anyone find or over rule my stash of the gear, one step short of the trash. Long banished and only I keep the stuff around. You will find that Altman gear also fits or can be retrofitted into the Century stuff.

On the other hand, it can become overwhelming with all the projects to be done can’t it? Start the punch list of what to do now and the five year plan of what is otherwise needed by way of priority. Take lots of notes and learn the system before starting much, than set up a schedule for getting what’s most needed first done now and the rest to follow. Remember the carrot on a stick or beyond this time off from the necessary work. After each project should come a weekend off or at least some project that is less priority and more out of personal interest. Also, do triage in doing what’s simple first in getting a bulk of it done first and now in any situation.

Say you have a bunch of cables with bad strain reliefs. That’s easy to fix no matter if the best of cable to be using or if to fixtures that need work or not. Takes time in repair but the payoff is immediate and payoff in starting with what’s easy first immediate before getting into more time consuming things. First comes the easy to fix and even if temporary in repair for now what will provide a band aid to the problem. Immediate and quick first, than project, than reward for work done by way of time off or special project, than next project and reward etc.

This or perhaps a goal for the day based system in getting a few projects done over a longer period of time. Say first part of the day is spent at the work table in doing what’s easy. After a while than the main project for the day done, than at the end of the day, ordering parts and or doing other things than project work.

Key to this is patience. It will all get done as long as you don’t stress it but on the other hand prioritize in getting what’s needed done first.


Patience is a good thing, along with ingenuity and a knack for pulling off what most think can't be done.

"We've done the impossible, and that makes us mighty." --Mal Reynolds, "Firefly"

Oh, interesting finding from some improvisational instrument repair:
Last night I had an S-4 go out. Bad lamp, or so I thought. Lamp was indeed bad, but mainly because one of the pins had burned out very badly and left crusty chunks inside the socket. Apparently it had arced and sparked and just burned up finally. Socket was shot.

Necessity = I only had 2 S-4's, both being used, needed to get it operational somehow, and short of trying to find another base from another house with an extra one, not a lot of options.

Discovery = the pigtail (plug, wires and, most importantly, the little contacts on the ends of the wires formed to hold the pins of the lamp (small brass contacts in a circle with a ring around them for tension on the pins of the lamp) of an Altman 360Q will fit, with a minimal bit of persuasion, into the porcelain portion of an S-4 socket, thus rescuing a burned-out base and unusable instrument, and alleviating much panic from our soon-to-be HS-senior lighting designer for our present show. --actually, the whole porcelain portion of a 360q socket will fit, with persuasion, into an S-4. Just something to keep in mind should time and circumstance dictate a prayer to St. MacGyver in order to get a burned out S-4 working.


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So what you are saying is that you took apart a TP-22 style Altman 360Q lamp base and inserted the contacts and porcelain from it’s aluminum shell, into the frame from the S-4. Interesting and very cool discovery. I knew that the S-4 had many things they studied about the 360Q but didn’t realize they were that similar. Been years since I had apart a 360Q lamp base in remembering what the contacts are like. Back in those days without a budget, if I had two bad lamp bases by way of the socket from the hot pin, I would disassemble both and make one good one. They kind of went back together okay as long as one used the screw mounting the lamp base to hold it’s pieces together. I don’t recommend it, but in the past it worked for me. Lamp bases are inexpensive - not good to be doing other than if you absolutely have to.

This what you did was a very interesting concept and while de-UL listing the fixture (insurance for should there be a problem), was a great idea for making it work that night. Expect you have already removed the other lamp base contact in it only being a temporary fix. It’s gold plating by the way on the socket. Very interesting, were they the same shape of contact in how the socket comes to a 90 degree bend before crimping to the wire? As said, it’s been years since I took apart a TP-22. (Very nice, don’t do it again type of thing of course. Spare parts are always a good thing to have on hand - better yet an extra pre-assembled lamp cap or two on hand to save lots of time is an even better idea yet.) Both porcelain insert and contacts fit? Very cool tinkering solution. Just make sure you also used the mica strip behind the contacts or it can easily short out.

Yes, the two HPL and Medium Bi-Pin lamps are both the exact same lamp in all ways except by way of heat sink - obvious and filament type. They are both a G-9.5 lamp base with a LCL of 2.3/8". A few years ago when Phillips was introducing the GLA/GLC series of lamp they even had a conversion kit for the lamp to make them work in S-4 fixtures. Had to drop the conversion kit by way of licence than later paid ETC to produce their own version of a HPL lamp proper. Never tried the GLC in a S-4 but out of curiosity I did remove the sink off one lamp and insert it onto a FEL lamp. Fit well and I installed it into a S-4 fixture. Worked but due to it’s huge filament the beam was crappy.

In other words, the only real difference in lamp bases would be one is set up for a heat sink, the other most frequently uses the fixture lamp base itself for that heat sink. The HPL concept is probably slightly better by way of ensuring the lamp says on axis to the fixture as opposed on the TP-22 that can at times be inserted at a slight angle due to tolerances. There is also often a little more to grab in removing the lamp without breaking it.

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