Longer life BTR?


Active Member
I bet Ship will be able to answer this one...

We've got a bunch of Colortran 6" fresnels that currently have 500w BTL lamps in them. I want to upgrade a few of them to 1kW BTR, but I want to keep the longer life of the BTL. I'm not too concerned about color temperature; I'll gladly give 150° of color temperature and a little light output for a few hundred more hours...the budget here is really tiny, so I want to get as much life out of a lamp as possible. Is there such a lamp that would fit?
When one goes off the beaten path in custom buying lamps that are not that popular, one pays extra for those lamps. Balance this by way of any longer life the lamp gives you.

Balance this also with for each 1% change in voltage, lamp life goes up by 3.6%. In other words, were you to trim your dimmer these were on so it maxed out at say 108v, your lamp life would be 3.6% longer when operated at full.

Is 1Kw BTR lamps what is rated for your lighting fixtures? If not rated for a 1Kw lamp, there is normally a good reason not to use the higher wattage lamps. Why skip the 750w BTN lamp anyway in going brighter? This especially when not concerned about color temperature which would be similar to output in what you give up when going long life lamp.

Ok, let's take a look. First, don't expect too much. Since the P-28s lamp base (Medium Prefocus) is not used other than for the most part entertainment industry 6" fresnels, and the entertainment industry is only a small amount of annual sales for lamp companies, there has not been much improvement on this lamp since it went halogen. Initial thoughts would be you can't do much better on life.

Onto the details:

of 500w lamps:
CZX/DAB, BTL, BTM, DNW, DMX are your lamp choices at 115-120v.

BTL is rated for 750hr and is the best lamp in this class of lamp for life.
BTM is rated for 100-150hr in being the high output halogen version of the BTL.

DNW is the incandascent version of te BTL and is obsolete. You can still get it from some companies as with some of the below, but the only thing you achieve is a non-halogen lamp which has a lower color temperature and shorter life.
CZX/DAB is a incandescent high output version that is obsolete to the BTM in all ways thus useless.
DMX is wile incandescent is higher output and color temperature than the BTM, but only half to 1/3 the life of it thus also useless.

Of 750w lamps, Strangely it's only a 500 hour lamp available. If you are noticing the difference in lamp life between a 500 and 750hr lamp, you are by far more in dept in touched with your equipment or more perminant install watching the clock than anyone else but still the BTN is the best of the class.

This amongst the DDB, DDY, DGH, DPJ, BFE, & BFL/BFK still available or discontinued as suitable lamps in that wattage.

On 1Kw lamps, you have the BTR (nrmally used on the discontinued 1K Beam Projector) and the DFD, DFT, DRB, DRB/DRC, DRB/DRC-5, DRC, DRS & DRS-5.

Normally something with a -5 after it means 500 hours or something of an alternative voltage rating. In this case, Wiko is using it to designate a 125v lamp that's rated for 25 hours while at 125v.

The 1Kw BTR is rated for 250 hours. That's not so good so I see your pain. Darned good lamp, better than a FEL used in a lot of Lekos.

Of all te above lamps however, there is nothing better or any lamp above in this wattage that even gets past 50 hours.

You could do a DWK, FKN, FKD, or Lif Code T-14 lamp as an alternative in choosing from 230 to 240v and about endless life but your output would be about minimum.

The PHilips FKD is rated somewhere between 900 to 750 hours while operating at 240v. This would mean you have a 324,000 hour lamp when operated at 120v.

Should you want extreme long life, go wit a 220, 230 or 240v 500w lamp suc as the ANSI Code FKF, Philips 437C/01, 559C, #6800C, or GE - Lif Code T-28 or T-17. I kind of doubt you will see any of the 220-230v lamps die out ever on a 120v dimmer system.

There is another class of P-28s lamps on the market but they are 3.1/2" long in lamp center length or focus length. Such lamps won't fit well into a Fresnel and would provide a very off center beam of light. Some of these lamps are rated for 2,000 hours however if you really really want the long life and given it fits, you don't care what your beam of light looks like. Look at the EGM if that's the case.

Your only other options it would seem would be to buy other lighting equipment to do the 1Kw output job.

Choices in this would be the ETC Parnel which by reviews is not really a classic type of Fresnel beam of light you would have to get used to. This in a axial mounted 750w long life 120v lamp would get you about a dim 500w high output wort of light at best.

Oterwise a 8" fresnel in not checking would probably have some longer life lamps available. This or move into the movie/studio Fresnel range of light that would have about a 4.1/2 to 5" lens but use the above 2,000 hour EGM for a long life 120v/1Kw lamp and other long life other wattage lamps.

Good luck, perhaps a final solution might be to use two fixtures in the place of one.
I was thinking I was going to have to go with the 750w BTN. All of our fresnels are current Colortran models (half were bought this summer to replace our old Electro-Controls fresnels with asbestos wires). They're rated up to 1000w, so there's no problem there. Compared to our 575w Source Fours the 500w lamps look pretty dim. Specs say I can get 17,600 lumens out of the BTN, and 11,000 out of the 500w BTL. So that should be quite a noticable difference.

Now that we have the dimmer capacity we can afford to go higher wattage and thus brighter. We had old Electro-Controls dimmers and slider patch board which had 15 dimmers, 2 60A (really one 60A sice the other was flaky) and the rest 30A. We had to limit our wattage in most of our instruments to stay within 30 amps. Now we don't have to worry about it since we have enough dimmers in our new ETC system that we don't have to double (or triple, or quadruple) up instruments on dimmers.

If my research is correct, we should get a little more life out of a 120v lamp since the voltage at the end of the connector strip is more like 118 volts due to line losses. And we don't run everything at full all the time anyways, so that will also contribute to the overall life.

I also have another question...how do they get these long life HPL's to last 1500-2000 hours?

Meanwhile I'll be waiting at the loading dock for our shipment of more new Fresnels and Source Fours! :D 8)
You are correct about eeking out some more life in a 118v circuit as well as in a circuit that is dimmed.

On the other hand you are also touching on something in general that is all combined when you note how dim your fresnels are compared to the S-4 fixtures.

This dim appearance is less due to luminous output than the fact the 115v lamp of the S-4 fixture is being operated in a condition over it's rated voltage. (A Leko should have a brighter beam than a Fresnel by way of luminous output otherwise.)

When you lower the voltage on a lamp below it's rated voltage, lamp life goes up and color temperature in addition to luminous output goes down.

The fresnel is going down in output as opposed to the leko going up. What you see however is not really the light output in saying it's dimmer. Instead you are seeing the difference in color temperature which changes 0.4% per percentage of voltage change. White is white but only in comparison to other light sources of greater or lesser color temperature. Just as a normal cool white fluorescent lamp seems brighter than an incandescent lamp, the Fresnel should look more dim tan the S-4 Leko. Remove the Leko and your Fresnel looks white again.

Also as opposed to the Law of Squares or Law of Inverse Squares where Luminous output drops by the square of the distance of lamp to target, color temperature does not drop with proximity. You can have your Leko 100' away and the Fresnel 10' away and in judging by brightness and not luminous output, the Leko will still be brighter.

Your BTL at 120v should burn somewhere between 2,950°K and 3,050°K depending upon what brand it is when it's new and is never seeing sufficient voltage for the filament to get that hot. Thus you have amber shift to some extent even when at the dimmer's full.

(Always note that it's possible that your dimmers might have 2v of voltage drop between the dimmer losses and in general cable, or it could be how your dimmers are trimmed in choking some of that voltage when at full. Should you wish to get a lower voltage, you can trim the dimmers to a lower voltage to save more in lamp life.)

Not enough amber shift while the BTL is at 118v that it's not a white light still, just a more towads red in scale of white as opposed to or in comparison to the HPL lamp in general which is operating at 118v over it's rated voltage still and as below already operates at a much higher color temperature.

The standard High output/short life HPL 575w/115v lamp starts it's color temperature at 3,200°K and goes up to 3,265°K when at 115v and goes up from there it's color temperature. It's also a more modern design of a lamp and should have more stability over it's life in color temperature and luminous output. This as opposed to the BTL that was invented in the 1970's which while it has the halogen effect working for it, the bulb and filament are not as effectively designed to maximize output and life.

This on average 200°K difference in color temperature by the way even if both are at their specified voltage rating is the difference in color temperature between that of a standard incandescent lamp and that of a standard halogen lamp. Just as you most likely would notice the difference there, you should with the HPL lamp.

(This in part is why when the HPL 575w/C lamp came out with the S-4 fixture, it was said to be as bright as a 1,000w FEL lamped Leko. While in reality it's lamp is nowhere close, perception in how much whiter the light is, a more efficient filament and fixture and other differences including operating voltage all made the HPL seem like that of a FEL. I more consider a HPL lamp to be about 800w that of a standard 1,000w halogen just as I consider a standard say 500w halogen to be about that of a 750w incandescent lamp.)

By the way, you still be able to get a 95v and 100v HPL 575w lamp juast as you can get a 64v instead of 77v HPL lamp for those with dimmer duplexing. (Below company also has some 77v HPL lamps.) These lower than normal low voltage lamps are a good thing to have about if you have a lot of voltage drop in your system - say a 110v after dimming amount of power at the outlet. This would maximize again that blue/white beam of light. DO NOT ATTEMPT TO USE A 95-100v LAMP IN A 125-115v SYSTEM. Operation of any lamp over 110% of it's rated voltage will cause premature falure if not dangerous rupture of the lamp.

Unfortunately the BTL line of lamp just as the EHD line is for the most part a dead end street for improvement on the lamp design. While they won't be going away any time soon, don't expect more than say pinch seal and other minor line of lamp improvements to them. There won't really be any radical design changes to them in the future. The FLK(HX-600)/HPL lines of lamps will get improvements and have already. The HPL lamps of today are improved in output and the FLK is replaced by the GLC and now better than a HPL or GLC is the HPR lamp with it's internal reflector. Sorry but at the moment it's not possible to install a internal reflector into a HPL type of heat sink based lamp, but the normal medium bi-pin lamp definately has an improvement on it which is 15 to 20% more efficient than that of a similar HPL S-4 Leko lamp. In other words, as I mentioned elsewhere, my 3.6Q6 Altman Leko kicked the rear out of a 30 degree S-4 Leko in intensity at about 60 feet two weeks ago this inspite of the Altman having a wider beam angle to start with. Same color temperature, just much more efficient lamp in luminous output even if installed in a less efficient and wider beam angle 20 year older in design lighting fixture. Install a HPR lamp in a Shakespeare, or modern Strand and either would easily outclass the ETC S-4 fixture. Same with a while non-reflector lamp but improved 750w lamp being better than that of the HPL 750/115v of the S-4.

Osram and probably other companies are working on a reflector for the HPL series of lamp, but at the moment it is too complex a filament to do so. This compact source filament is probably better than that of the same basic lamp in it's class the GLC(HX-603 or HP-601 dependant upon who you ask). But compact source filaments is by square or cubic area of the filament only one way a lamp can become more efficient.

Used to be Osram used to make a part #54582 1Kw FEL lamp that had a internal reflector. This was a lamp years before it's time, but one that never got much attention just as their HPR 575/115v lamp I seem to be one of the few in the industry attesting to so far. Cause of my concern is that the FEL-R lamp was discontinued due to lack of sales in it, and I fear the HPR lamp will also in the coming years fall to the wayside as a side note in others not recognizing that it's light years more advanced than a HX-600 or FLK or even GLC lamp.

Imagine if you will this FEL lamp I call barbaric due to the size of it's filament thus really bright beam of light (there is others even more bright still than a FEL), but one with an internal reflector that will provide 15 to 20% more light than the stock FEL still. This if not even more efficiency since the reflector is orientated in the direction you tend to want light to come out of. You will of course note that the FEL was a 120v lamp and there has never been a EHD/EHG/FEL lamp of 115v. This is where the HX-600 to HX-605 line of FLK/GLA to GLE and #6981P line of lamps come in.

Confused about all these HX, HP, HPL, HPR lamps yet? Much simpler to call them by a three letter ANSI coded lamp standard such as the HX-600 lamp became the FLK, the HX-602 became the GLC, the HX-754 became the GLD etc. The HX-156 1.2Kw PAR 64 lamp became the GFE etc. It's not only a question of Leko Lamp lights in the end.

Thrill your friends and piss off your suppliers in correcting them when they call a HPL lamp a ANSI lamp. There at this point is no such thing as a ANSI coded lamp that starts with "H". Anything with a H in front of it is dependant upon the type either a halogen version of a sealed beam lamp such as a H4515 or a experimental version pre-ANSI coded temporary experimental version of a lamp.

The HPL line will probably never get a ANSI code to them because unlike normal ANSI lamps, or even experimental lamps, they use the same code no matter if long or short life, what wattage it is or what voltage it is, or even when drastically changed or improved the same letter code.

This as opposed to the GE/Thorn based system of assigning one experimental number to a specific lamp type which easily translates to a ANSI code. It's even dependant upon what manufacturer you talk to as to which lamps get a HP designation verses what gets a HX designation. The HP-601 is the same as a HX-603, though the HX-603 started it's life out as a 120v lamp, and Philips says they invented the actual GLA lamp and the HX-603 is nothing like it. HP could either mean an alternative to a specific HX lamp by way of further improvement to it, or parallel filament coils instead of coiled coil filament coils even if parallel also. Gets complex the differences between say a EHG, FLK, GLC and HPL lamp by way of filament. All are similar to some extent, it's just a question of cubic area and structure to how the grid of filament is arranged. Such is also enough to get one ANSI code designation per lamp type.

The HX-600 became the FLK, the HX-601 never got one because it's not that efficient or not enough lamps were sold amongst many suppliers (people incorrectly call it a FLK-LL instead of the HX-601), the HX-602 became the GLC, the HX-603 the GLA, the HX-604 arguably the GKV, the HX-605 arguably the GLB, HX-754 the GLD, HX-605 the GLE, HX-156 the GFB etc.

The HPR lamp if it were to become an industry standard would get it's own ANSI designation as long as it remains one specific unique to other versions type of lamp. This given it's a popular enough type and possibly other companies start making it. Also as long as Osram does not develop a 750w or long life version of the lamp with the same designation, it like the HX-600 is all set. The long life version is in the works as I am shure the 750w version. Until than, GE/Thorn make the long life GLE 750w lamp which is for the most part similar to that of a HPL 750w/X (extended life) and Philips makes the #6981P lamp for the HES Color Command fixture which is more powerful than that of a HPL 750w/C or GLD lamp.

Most manufacturers follow the ANSI code for lamps - you note above some notes about color temperature "dependant upon who makes it."

Philips is also getting away from following the ANSI system on some of their lamps. This is possibly since they are upgrading some of their line to improvements that no longer make the lamp qualify as a ANSI lamp. That's a slight downfall to the ANSI system. There can be some variation in the actual lamp specifications but not by much. Lamp to lamp a ANSI lamp is the same lamp. Should you wish to improve it, or say do a black reflector as opposed to silver, stippled verses Fasceted verses Dicroic, verses blue dichroic, verses Neodymium, verses white, blue or even colored or clear reflector colored and coated reflectors, or smooth, specular reflectors, or even a MR-16 lamp with a lens on it, these ANSI coded lamps become one huge mixture of lamps no longer similar. This all available in addition to at times a 60 degree in addition to a more normal say 36 to 44 degree beam spread normal under EYC ANSI lamps of just a say MR-16 lamp used in say a cyc light fixture.

This given a Xenon filler added to the halogen gas will have a huge difference in ability to have a higher color temperature than that of one with say normal halogen or even those with a krypton (remember green) filler. Some lamps have color correcting filters etc. While the ANSI coding system for a old Altman EHD lamp is a good thing, it's especially with low voltage lamps getting really complex when even for one ANSI lamp - especially the low voltage types, you have about 6 or 12 choices for what in general qualifies for the same ANSI lamp. Was that a axial or transverse filament you wanted in your capsule lamp? Both can have the same ANSI rating possible.

Thus it's not just say the HPL series of lamp at fault or say Philips in beginning to loose the ANSI code for more and more of their lamps this stock standard. Lamps are in fact becoming really specilized and complex in having so many things you can do to them. For instance, in some of the first posting of the BTL type lamps, some of the options for use in the fixture I posted had blackened tips to their bulbs. Would such a detail matter in a Fresnel? Not in any way would it matter yet such detail might be important in another fixture thus it had to have a different ANSI code. Were by the options available today all lamps ANSI coded, we would easily be into a four letter code system by now.

A HPL or other "H" series lamp has no similar mandates as to one lamp to another both being similar thus can mean more than one thing. In the past before improvements to te lamps for instance, you could easily tell the difference between a Ushio and Osram HPL lamp. They are for the most part the same now but there used to be a large difference.

Expect internal lamp reflector will be the next major improvement to the HPL line - internal lamp reflectors that complete the ellipse of the reflector. This in addition to dichroic coated glass to maximize the re-use of IR heat that otherwise gets wasted. There is some lamps such as the DYS for Ray Lights that dependant upon the brand already have a dichroic coating inside the lamp to maximize heat energy in sending them back to the filament, but at the moment no T-Shaped glass lamps.

Don't expect any future improvements to the Fresnel lamp. Sorry but not even a write in campaign would make a BTL have a HPL's flament. Besides the reflector system in use is not efficient enough to take advantage of it. Not even a traverse reflector as available on some lamps of the past would be sufficient in such a was fixture. Old design that is no longer used enough to improve might be the manufacturer view point.

Anyway just some further notes on the subject of lamps.

Should you want about 30 or 40 BTR lamps, one of my distributers is getting out of the stage and studio lamp market and has that many left dependant upon how many I bought today from them today. (I had no use for all of them.) Bought them out of most of their useful lamps at least to te extent I expect to be needing in the next year. . About all that's left are the oddball or less used ones such as your BTR.

Contact me off line should you want the 1Kw lamps potentially at a really low price as a one time only deal directly from them if you buy all of their stock out. I have no interest in this sale nor want it to be other than a valuable solution to your innitial request of which I will not be taking part.
I will forward you their contact information. Otherwise, should they not sell direct they should be able to tell you who your local supplier is that has an account with them. Otherwise I could look further into a bulk price for them thru where I work. I do not advocate sales on the forum nor is it my intent to sell stuff other than if it like is in this case is not something otherwise nromally or easily available such as this closeout. This is also someting to be taken off line also.
Onto the question of what makes one lamp a long life and another a high output lamp when they both have the same wattage, voltage and filament type and size.

This believe it or not is one that's really hard to find out about even when talking with engineers at the manufacturers. While in meetings with them I have asked more than one manufacturer this question and never gotten a more simple response than a in general, it depends upon the amount of "doping" of the materials and metals making up the filament which determines the expected life that filament will last. This is also studied in the Osram low voltage lamp free PDF I have noted elsewhere on the forum many times such balances about lamps the book goes into. Darned good read.

In further detail one must study the term "doping" of the filament. What this means is that the tungsten filament of a lamp is not just tungsten but a sort of alloy of it. Tungsten by itself is rather hard to work and refine, much less can if I remember correctly be very fragile and while longer in resisting breaking while incandescing during resistance to current, has it’s own problems. It also burns as a norm for all tungsten lamps at somewhere between 3,500̊K and 3,600̊K depending upon what source you are reading info about it from. This is were color temperature of a lamp directly relates to how hot that lamp is burning and how much of the filament is burning off or how short that lamp will melt thru as opposed to burn for 100 years. It’s also metal so keep flexing it or heating and cooling it and you get something that will become brittle. Below will be a mention of a bell curve in color temperature. While for the most part in the section of seating in class at school certain members will be at the lamp’s rated color temperature, other parts will when on a bell curve be getting better grades in school and others lesser grades in school such is the bell curve rater than linear curve of light given off by the lamp. A 3.2K lamp does not just have a color temperature of 3.2K, it’s all wavelengths - this is just the main part of the light provided. Those amounts of the color temperature of a lamp at 35K or above will tend to burn up and burn off the filament, while those cooler parts would tend to last longer. What is done in doping the filament effects to what extent the filament is allowed to approach surpass 3.5K and in general dopes or dummies down the bell curve of color temperature that lamp burns at in general. In other words, it’s making a 120v lamp into a 130v lamp, or high output into a long life lamp, or changing if most of the class received a “D” for a grade, them thus all getting “C’s.”

While the above 0.4% ratio above that of the change in a filament due to percentage of voltage applied to a lamp might seem small, remember we are talking about lamps that for our purposes have between 2,800̊K and 3,500̊K in color temperature ratio. 0.4% Than when over a couple thousand adds up for each percentage. This especially in the 3,200̊K range of color temperature for a stage and studio halogen lamp which due to the "halogen effect" re-deposits spent/burned up parts of the filament back onto the filament so it burns again, to some extent there is still some wasted filament getting lost or deposited on the wrong parts of the heat source/filament.

Note due to air flow circulation witin the lamp, what is burned up from some really hot parts of a lamp - such as near the center of a AC lamp or near the (-) side of a DC lamp, will get instead of re-deposited back where it burnt off, instead by air flow get deposited onto the more cool part of the filament thus would be why even a halogen lamp will die out.

This is the halogen effect, while the iodine and other chemicals within the lamp does catch particles of filament and re-deposit them, the hottest part of the lamp is simply too hot in heat pressure to easily re-deposit filament back onto it, much less some particles get trapped in less efficient parts of the bulb shape. Now get into some even more rare than iodine type chemicals such as Krypton (somewhat in green color temperature) and more especially Xenon that is really rare, or I expect radioactive forms such as KR-85 and add that to the halogen mixture of bromine/argon/iodine and other chemicals in the gas of a halogen lamp, and you have a lamp that better can handle high temperatures and re-deposit the filament where it's needed.

Xenon fillers are really expensive but absolutely necessary if you want to operate a lamp near the melting point of tungsten if even for a short period of time. For the most part, you won't find xenon filled lamps for other than say the HES Trackspot that uses a xenon filled lamp that is only rated for 50 hours when operated at or near the melting point of tungsten in general. But what a 50 hours in intense beam of light there is. You can get a longer life version of lamp for the Trackspot, but you quickly get into a more halogen version of it's color temperature and lower output. No matter what chemicals you add to the halogen effect to make it more efficient, at some point the general rule of exchanging 3.6% output and 0.4% of color temperature for each percentage of voltage difference which reduces or inversely lamp life by 12% (dependant within 1% what source you read), this is a rule of thumb one cannot much get beyond too much. A 130v lamp is often rated for the same amount of output and life as a 120v lamp as a 115v lamp when operated at the specified voltage. All a question of rated voltage in providing the same specifications while especially operating at other than that specified voltage/volume.

To some extent a HPL or modern lamp might have some xenon fillers to them to allow them to burn hotter, but not a lot of it in the lamp is affordable or to a great benefit at the moment.

In addition to reflector qualities of the glass surrounding a lamp, you also won't find much in the way of xenon fillers. A T-Shaped bulb is just too inefficient in where that heat flow is going to increase the color temperature of a lamp much more. Think of a tube of glass with hot spot in it's center. Than a great wind inside of it and that's the halogen effect. While a lot of that wind will circulate from cold to hot back to the filament, some of it is still going to get less pressure in going back to the filament and instead become a sort of tornado of lower pressure in never getting back to the filament towards the extreme ends of the tube of glass not closest to the filament. Thus some of that tungsten filament is lost to replentisment also in addition to the re-deposited metal preferring to re-deposit on the slightly more cool part of the filament due to pressure/heat. Hotter parts of the lamp such as those on a DC system where the current comes into the lamp, or in AC where the center of the lamp, coils to the filament are warmed by adjacent coils in the filament have a certain amount of more heat conventional oven like applied to it than parts of the filament say towards the lead in wires where it’s less cool because there is less heat adjacent to it due to conductance to heat/light waves. What’s going to be easier to re-deposit the heavy metals of the filament, this to where it’s cooler and of less pressure or there where it’s hottest and re-circulated air is more pushed away?

This vacuum within a tube and various pressures within the lamp dependant upon where especially a T-Shaped Leko tube lamp will play a large factor into various pressures within the tube in the heating and cooling cycle.

For this reason also a dichroic coating within the lamp so as to convert IR energy/heat that otherwise is not used is not of much use within a lamp at the moment unless that bulb is a globe coincentric around the filament directly reflecting back to the filament. On some lamps, this reflected heat while light passes thru the glass, the IR is reflected back into the filament of the lamp in further heating the filament. You thus get a lamp that not only has voltage/resistance flowing thru it in getting hot enough to incandess - burn that filament wire almost to melting point, but also there is heat applied to the filament from the outside in getting it hotter still in needing less voltage/amperage applied thus wattage.

In the above, I mention a certain thermal effect proximity to what’s the heated part of the filament has to also in addition to applied voltage heating the filament of the lamp. The closer the filament coils in proximity to each other also the more efficient the lamp in other than resistance of the filament heating of the filament. This thus is in addition to a more compact filament shape being by way of reflector of the instrument efficiency why say a HPL lamp will be more efficient than a FEL lamp. Proximity of the filament grid as long as the amperage or magnitude of current in the filament is not sufficient to arc between filament coils tends to re-heat adjacent coils of the filament in making that say HPL 375w lamp as bright as say a 500w EHD lamp to some extent.

Since most of our Lekos have tubular instead of globular shapes, a dichroic coating on them to reflect the IR waves of light won't do much cost effective good but in changing the geometry of a lamp, it’s an option for the future in further heating the filament other than by way of resistance, that filament to incandess at a lower resistance to current. At this point it is probably more a question of given a specific dia. of a T-shaped lamp, and given a certain amount of volume inside a lamp needed for cooling what globe shaped dichroic lamp would be required to make for a replacement to the tube shaped lamp we currently use. Just as the T-4 dia EGE easily replaces the T-12 DNS in size due to halogen effect, it’s still a statement of cooling of the lamp. The halogen gas within the EGE allows for a hotter burning lamp but still has a certain amount of cubic area to it. Make a ball of a lamp instead of a tube and the dia. would need to increase. This in addition to the length of te EGE not really needing it’s extra length but due to the length of the old incandescent lamp it replaces, a globe of a dichroic larger dia. lamp would be required but on a longer stick of extension from the lamp base due to what lamp it replaces just as wit the DNS. Such a long extension is also fragile and prone to failure as another obstacle in making the S-4 Leko having a globe shaped dichroic lamp fit inside it. Remember that the larger the dia. of the lamp that goes into the light, the more of the reflector is cut away in fitting the lamp in. More of the reflector/ellipse cut away, the less efficient the fixture. Constant trade off’s in designing both lamps and fixtures and at the moment it’s probably in this dichroic coating to a lamp not possible given the fixture to upgrade more efficiently.

This also in lamp size and shape is complex as with every part of a lamp. Old incandescent Leko Lamp bulbs used to be T-28 and larger in times. (The T-Number designates the shape of the lamp, the 28 number designates how many 1/8" increments that lamp is in dia. No idea on why it's 1/8" increments but that is the measurement.)

Part of burning or incandessing is in pressure or ability to combust. No air or in this case pressures within the lamp surpressing burning up but not so over oppressive that it can't burn, and you get no combustion. Have a lamp with no pressure surpressing it's flame and you get a flame or melt down following it in resistance without restrictor.

First you have the vacuum tube as ancient in lamps. Remember them of you older tech people throwing household or better yet surplus TV lamps/parts at brick walls in listening to the "pop"? You won't find many vacuum tube lamps under 40 Watts these days. Argon, Nitrogen, Bromine and other high electron elements are much more effective in suppressing the burning up of the filament in a positive rather than vacuum atmosphere. A negative vacuum atmosphere when the burning of the filament causes pressure normalizes than becomes plus some AU. You than have a lamp that both resists both suck and push. Instead most lamps just have to resist push of pressure.

Something of a science class question or study into why something with a high electron or higher on the what ever that scale it is count is more resistant to surpressing the burning up of a filament but it's the case here. A argon filled lamp will surpress better than a vacuum lamp and be less dependant upon a good pinch seal of the lamp to work dependably. Why is it that Xenon is better than Krypton or Bromine otherwise?

So you have surpression of the filament as one thing that dictates how long a lamp can last in addition to globe shape. (Getting back to the subject.) A xenon filler will allow that filament to burn hotter or in the same theory if the filament is burning at a more normal temperature, should allow that lamp to burn longer at that temperature at only an increased price of the rare earth gas Xenon. Just as a halogen lamp lasts longer than a incandescent (lacking the special re-depositing of filament gasses and in no way otherwise for the most part different than any other incandescent lamp) you would find that a xenon filled stage and studio lamp would last longer in life than that of one that does not have it. This in addition to kryptoin in small amounts is already done to some extent that is higher output but still cost effective. Krypton is another type of filler above the halogen mixture that will add to burning or operating temperature. Not because of Superman comics but for other reasons, kryption as a chemical still is not as high in burning temperature as xenon fillers but +has a green tint to it.

The shape of the lamp also will play a factor in how well those gasses are able to halogen effect the spent filament back onto the in-tact filament. It in those more or less lost zones of the bulb shape in a low voltage (more architectural lamp) while under dimming can be burned as a lamp too cool for the halogen effect to take place with instead the iodine corroding and attacking the molyodenum foil of the lamp (where the wires or pins of the lamp transfer from pin to wire witin the pinch seal) or the glass attached to this piece of metal in having dimmed halogen lamps that at best work as well as a incandescent lamps, at worst last a shorter amount of time than one. Don't worry, 120v lamps burn hot enough that even dimming to 10% is sufficiently hot it's not a problem. Low voltage stage and studio lamps such as in a 12v cyc light using MR-16 lamps are also safe in theory due to the in series operation of them. Just an individual low voltage lamp when dimmed that could have a problem with getting hot enough due to the shape of the glass and how that wind within a halogen effect lamp works.

On the other hand also most companies have come out with their own improved pinch seal technology no matter what the voltage or type of lamp. P-3 tecnology from Philips being the most famous and published amongst all brands of similar technology. 120v and arc source lamps also have pinch seal problems that while not persay the filament not getting hot enough, this is the less efficient part of the lamp and one where once pinched tight to hold the gas in, it also offers an exit to the gasses within the lamp.

So we have bulb shape and wind flow. Related and specific to this we also have bulb shape which effects as if the tube of glass were a reflector as in a interior coating of dichroic metal particals a internal lamp globe reflector that's not really possible for most stage and studio lamps due to shape. At some point, once a more high temperature xenon gas (expensive) is introduced to more extent to the globe of the 120v and high wattage lamp, you can expect that the lamp shape/quartz glass can also be reduced in size or at least become more reflector in shape in reflecting the IR heat once dichroic coated back to the filament the otherwise useless heat of the lamp. This will reduce the wattage of the lamp necessary to heat te same lamp due to wattage/resistance once warm.

Otherwise an alternative is to as with some liquid filled xenon lamps used on IMAX theater lamps, do a liquid filled instead of gas filled lamp so as to further reduce the temperature of the lamp thus allow it to burn hotter still. This liquid filled lamp technology is still years off I think, but raises certain worries amongst lamp engineers when you mention such concepts. It’s either some deep secret or some worry about other manufacturers technology above their own. In a serious way, slip in the concept of a liquid filled say HPL lamp and it causes instant interest with the engineers. Don’t know much about how such a liquid filled lamp works, but I expect they also don’t yet.

And now back to what it takes in difference between a high output and long life lamp in "doping" or to the best of my knowledge in I'm a Master Carpenter by trade but did buy a few $K in lamps today description of my understanding of the subject.

Ok, I work as the lamp buyer for one of the largest 5 or 10 lighting companies in the world and as such in the last about 6.1/2 years have had to learn the specs on what I buy in detail over hearing a Menards commercial for "halogen lamps" and thinking that they have some magical brightness quality to them in general (note the above incandescent fresnel lamp that is higher output than that of a halogen version.) I also have to field requests at times from famous designers normally by way of corporate show account executive requesting a halogen lamp that is daylight in color temperature because that's what their design calls for. Here I am still carpenter by training for the most part before now in saying, urr, the filament of a incandescent heater/resister filament burns up at about 3,500̊K so it's not really possible to purcase any 5,000̊K filament halogen lamps. Perhaps Menards with their “halogen” lamps might help you with this request instead.

While you can gel or get some coatings on the lamp to make it seem that hot, you also will loose a wee bit of light in what such light waves - most of it's beam in a curve from about 1,200̊K to 7,200̊K is being blocked. (My estimate) Color temperature is where the bell curve of color temperature averages out but it's drop off is steep in providing only a little light in the 5K spectrum of light. This is why incandescent lamps don't make good UV lights (some but not much UV-A spectrum) and why the incandescent lamp is more like sunlight in natural light than an arc source of light - fluorescent to moving light. Such lamps have a sort of bell curve also but instead of a gradation to it's beam of light with all colors making up the white light, it's more spikes of light in certain wavelength designations and not a full spectrum dependant upon the refinement of the lamp. What a arc source lamp looks like under a prism would be related to it's CRI or color rendering index - another subject.

In getting back to filament lamps and why one type of lamp having otherwise the exact same specifications as another lamp can be of longer life we look at what other metals and compounds are alloyed into the lamp's filament to make it last longer in exchange for burning up really fast. This in addition to the above filler and globe shape.

It should be expected that no tungsten filaments are completely tungsten. This tungsten was a filament metal that in history was found early on necessary to while it is most effective as a resistor, not a efficient piece of metal to shape as needed, or easy to keep long lasting. Instead other things are added into the metal.

How much say steel is added with the tungsten might determine how well the filament in keeping the exact same size of wire or has some amount of shock resistance such as the difference of when a filament has to heat up from cold, it allows energy to resist the flow of current as opposed to let it flow easily and not burn up as fast. Should on the other hand you increase the size by way of dia. of that filament wire it cold handle more current. On the other hand should you reduce size or lengthen the wire it would resist more current.

So and this gets beyond my main study, at say 120v, you would tend to need a more thick filament size or say two coiled coil filaments to produce more current to flow thru the wire than a filament say designed for 110v. In resistance and given the same material making up the wire, the less resistant to the flow of electrons, the less incandescing that filament will be and also better able to deal with heat that filament will be. A 120v lamp will have less resistance than that of a 110v lamp given all else is the same other than what is necessary to make the 120v lamp have the same resistance to current as the 110v lamp which by way of lesser voltage needs less of a resistor to it.

So in size of filament and it as length, the smaller the size and longer the length or any combination of that you have, the more resistance you also have. More resistance equals more heat thus more light and wattage. This all assuming the same voltage rating on the lamp. Higher the voltage rating in considering size or length and you increase the resistance of the wire. Resistance equals to some extent work done or wattage thus in gaining the same wattage of lamp but for a higher voltage and you need to increase the size of the wire or shorten it's length to compensate just as if you were to hire it's wattage.

Stainless Steel has more resistance to current flow than Aluminum. Copper has less resistance than Aluminum. Gold less resistance than Copper, Platnum less resistance than Gold. Given these slight details to current flow and others, change even the percentage of these metals within a filament and you have something that in keeping the same size and length of a lamp’s filament will either increase or decrease the lamps life. Granted in doping of the filament, you get less resistance to current thus less wattage or output/color temperature, for the most part in this way you do increase lamp life. Cooler that filament incandescess as or further away from 3.5K it gets, the longer it will last.

This is a prime difference in what goes into the doping of the filament of a lamp, why at the same voltage and wattage rating, much less filament type and size you can have a both long and short life version of the same basic lamp.

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