EHG Replacment - EHD, GLA, or GLH?

[BobHealey]

Hello.

One of the theaters I'm the lighting chair at has the lighting designers and directors constantly complaining the system is way too bright. Right now, the front wash consists of old Altman 360Q (with the yellow UL labels) 6x16s and 6x12s lamped with FEL (I know, I know, I know, my predecessor did that) and EHG. Its very rare to see any of the ellipsoidals over 50% intensity on the console. I happen to be completely out of spare lamps and am actually raiding other unused fixtures for replacements when I blow a lamp. So, I need to order a metric ton of spares once the budget year rolls. Since most people seem unhappy with the maximum intensity, I'm planning on going lower wattage. Trying to figure out via lumen tables if I want to go EHD (500W), GLA (575W) or GLH (375W). The GLH is a 2900K lamp, which is a downside. Everything else is going to get bumped down to next lower wattage. 6" Fresnel to BTL from BTN, 8" fresnel to retired, S4 PAR to HPL-575X from HPL-750X, S4 Jr Zoom to HPL-375X from HPL-575X.

Unfortunately, I can't find any old Altman 360Q data sheets to compare EHG/EHD to in the 360Qs to see how much performance I'll gain/lose going to the different lamps.

Any thoughts?

 

[derekleffew]

I'd try to make everything 575W and as long-life, with as consistent a color temperature, as possible. This means GLA in your 360Qs; FEL/EHG/EHD are old, inefficient filament designs. BTH in your 65 F.S. HPL575/120X in all your S4 products.
By stocking only one lamp per base type:
1) you simplify your ordering, and
2) eliminate confusion of putting wrong wattage in wrong fixture.

To calculate performance with the GLA, use this sheet: http://altmanltg.com/altman-lighting-ellipsoidals/Ellipsoidals/360Q/shakespeare-ellipsoidal-360Q.PDF , and use the formula (GLA initial lumens 13,000 / GLC initial lumens 15,600) = 0.83 to derive a lamp multiplication factor (cut sheet calls it "Correction Factor").*

Thus a 360Q-6x16 @ 40' will give you the following foot-candle readings with various lamps (in a vacuum, excluding friction and gravity, in an ideal world):
FEL 255 F.C.; GLC 145 F.C.; EHG 143 F.C.; GLA 120 F.C.; EHD 98 F.C.



*(A lamp's initial lumens and a fixture's BCP do not correlate exactly due to the filament configuration, but the above should be close enough for our calculations.)

 

[BobHealey]

Making the assumption that lumens are directly scalable with dimmers, running 40-50% on EHG indicates I should be looking in the 6,000 - 7,500 lumen range, which seems to point back to the GLG/HPL 375X, despite the color temp shift.

 

[derekleffew]

Making the assumption that lumens are directly scalable with dimmers, ...

A very flawed assumption:
lumens/LUMENS = (VOLTS/volts)^3.4
plus the fact that it's highly unlikely your dimmer curve is linear. But let's say it was. 100%=120V and 50%=60V. The EHG has initial lumens of 15,400. At 60V, it would be 1,459 (9%). Now let's use the numbers from this post, and say that at 50% your dimmers are outputting 80V. At 80V, your initial lumens are 3,880 (25%).

I say it's worth buying one each of several different lamp types/life/wattages and compare for yourself, with your fixtures and your dimmers, before making the decision. N.B. Rarely if ever have I encountered designers/directors telling me the lights were too bright; it's virtually always the opposite. Lucky you. Can I interest you in some neutral density?

 

[dramatech]

Last year, I changed all of my Altman 360Qs to GLA lamps from EHG. We have now done about 8 shows with that lamp configuration, and we love it. First of all the GLA lamping appears to be brighter than the EHGs were. With a lightmeter, It actually was just a few footcandles less. I think that the color temperature makes it seem brighter. The fact that we are burning 575 watts as opposed to 750 watts is a real plus and the GLA seems to match the colortemp of the HPL lamps much better. OUr LDs are really pleased with the results. We chose the GLA over the GLC because of the extended lamp life. At the time, we were hurting from the economy and wondering if we would last a few mroe years. We have done really well since that time, and are now financially secure, at least for a while. As our HPLxs and GLAs die off, we are going to replace them with regular HPLs and GLCs. While we are happy with the longer life lamps, we want just a bit more brightness.

Tom Johnson

 

[Sayen]

Just as a follow up question - I'm running Altman Shakespeares in with my S-4's, and have similar issues. I can take some good lamp guesses from this thread and others, but any advice on lamping those?

 

[BobHealey]

A roll of neutral density might be a solution. I wonder how fast that burns on a 360Q - I've yet to meet a color I haven't burnt on those. Yes, that includes no color pink and blue. I've got plans to strike everything this summer, clean it, and bench focus it. Will probably make my intensity problems worse once I clean of decades of sawdust from the optics. Personally, I'd like to throw GLE or GLA in everything and be done with it, but I want to make the artistic side happy, and that means getting rid of the red shift making an R60/R33 plot turn into "warm and warmer, why didn't you hang any cools for this show?"

 

[ship]

So I'm thinking What? in HPL refrerences of this subject, and or if director is talking "way too bright" with FEL's but the dimmers at 50%, and this post of GLA's comes up for answer. Good answer.

1KW lamps too bright given amber shift at 50% dimming.... that's a problem only going back to a EHD perhaps could solve and only in better yet a GLA can now solve in better lamp.

GLH lamp... never heard of it before, anyone a link to it? (Sorry really really busiy these days in making copies of really old lights and museum work. Totally not up to date on lamps recently.)

 

[BobHealey]

GLH - 375W lamp, long life. Right now, using a mix of FEL in 6x16 and EHG in 6xeverything else. For the current show I'm op'ing, max console intensity is 80%, average is 60%. Show is Fiddler on the Roof. Have also gotten excessive brightness complaints from designers/directors for Ragtime, Aida, and Baby. Ragtime wasn't permitted to go above 50%. I'm going to be buying some GLA and GLHs to do a comparison. Plenty of EHD in stock, almost no EHG left, and FEL I'm pulling from spare instruments. I've got some 6x22s that have GLE's loaded (experiment in modern lamps, failure due to too many usable lumens). I've got a unique opportunity to relamp this place with better lamps.

 

[ship]

Wow an amazing selection of lamps. Off line response in figuring out goal of long life concept and proper output. Lot of lamps and fixtures to maximize. That plus the specials.

 

[BobHealey]

Just as a follow up question - I'm running Altman Shakespeares in with my S-4's, and have similar issues. I can take some good lamp guesses from this thread and others, but any advice on lamping those?

Just saw this post, the school theater at RPI switched their Shakespeares from HX-601 to GLE to go with their HPL-750X lamps, and to SPH to match the HPL-575X lamps (two different auditoriums, with different power limits) last year and has been fairly happy with how well the two match. This isn't the theater I was asking about, the RPI folk use the most wattage they can get away with in a space. I'm currently working with 4 different theater groups in 5 different spaces with 60's to current gear.