Depends on your situation.
For a club or theater, it might be beneficial given all lamps have about the same lamp life to swap out all at once but for the industry in general, as it were say rock and
roll touring and or convention lighting, say ten or many more fixtures got sent on a tour, they come back and say half go on the next tour that might run such lamps into the
ground - 10% output and way past the lamp life, while others got instead got sent on a corporate
one-off show and came back. Than those fixtures got re-bench focused against brand new and other fixtures coming off a tour and or next corporate show. Once you mix and match the use of the fixtures in an inventory in say like ten tours at any one
point going on and like 20 or more corporate shows, plus new gear constantly coming in, it’s all about the individual
fixture as it compares to another and or the entire
truss of them in say a show that’s been out for a year now and already changed the lamps in the fixtures at least twice now -
truss section by
truss section beyond individual blow outs.
Just finished bench testing four of the new Philips MSR 1200SA/DE/2 lamp - (Unknown official name to it.) This was tested with a bench
mark brand new HTI 1200w/D7/60 lamp, a MSR 1200SA/DE and two +/- 300 hour HTI 1200w/D7/60 or
HMI 1200w/S lamps. All six brand new lamps seemed without pulling out the light meters the same - no difference, and brighter than the used lamps. This with optimizing each for performance. That’s not to say that all the new lamps as normal couldn’t be optimized as it were to match the older lamps or is for sure known that the older lamps were optimized well enough to match the new ones in a happy medium. Only said all three new lamps and of two brands looked the same on bench focusing, and none of them initially matched the used mid-life lamps.
That’s Philips and Osram as well I expect with GE/Koto because Koto for a brand was also an excellent lamp for the fixtures. Koto now makes all GE moving light lamps. On the other
hand at one
point where I worked switched to Amglo for a brand for most moving light lamps and many of the lamps we were using were brand new for them. Took some time for them to stabilize their production in fill pressure
etc. Lot number to lot number they had a lot of trouble in being the same, this much less in matching up to the above premium brands of lamp in both matching them and having a stable output that lasted for the most part over the life of the lamp. Took them over a year but towards the end of our contract they did do so. Same with Eiko in being new, no doubt Devine
etc. Main problem is in matching up to a bench
mark lamp. If say a MSR 250/2 lamp from Philips is your bench
mark, you expect it will match up to it from brand new to old in preformance this as an individual lamp and in matching up to other fixtures having that other lamp. Really hard to do. Devine lists their lamps for instance as direct replacements for the other lamps and they cannot be in that even the difference between a Osram and Philips lamp might differ and in testing they did. Neither or none bad but just didn’t
play nice with each other. The other brands have to be on their own or directly match say one brand not all brands because in that they fail. The GE CSD 250/2 SE for instance in testing matches up really well with the
MSD 250/2. The Osram and Ushio versions on the other
hand do not. Not to say they are not good lamps, just that if the Phillips is the bench
mark and say you have a hundred or more fixtures already with the Phillips, one needs to either stay Phillips or go with what matches best overall initially and over its lamp life. Each brand it’s unique lamp life and characteristics. The MSR 575HR lamp for instance will work on a VL-500A but the Osram
HMI 575w/SEL on the other
hand wouldn’t work dependably in the
fixture. Same basic lamp, little less fill pressure. On the other
hand in using a different
ballast the
Chroma Q
Daylight Par works just fine with the Osram lamp. This is an extreme but an example of situations that develop by way of say a GE lamp cheaper working just fine, but in some instances even if the same basic lamp the say Osram lamp not working at all even if the specifications are similar. IN testing the MSR 1200SA/DE lamp didn’t last as long or dependably as the HTI 1200w/D7/60. Philips came out with the next prototype to
address that I think - still yet to get product specs on what I’m
play testing. Who knows what in the end will be the better lamp.
Add to this wide ranges in
color temperature - about so you can by lamp choice tune in what
color temperature you desire the
fixture to put out - a difference between MSR 250, MSD 250 and
MSD 250/2 if I remember correctly in not checking my notes - amongst brands having a range of
color temperature plus as noted, lamp life hours, wide range in them. Some moving light lamps go 500, some 750, others are in the 2,000 to 3,000 lamp hour range (MSD types amongst brands) and some are even in the 6,000 hour range given a
drop in output for them at least but often more output on the MSD lamps than MSR lamps as an exception.
On the other
hand, just bought some lamps for a customer. They were looking for 150w R-40 lamps for their
stage. Sorry, ran out of sources for such a lamp in no longer really available for a
stock incandescent lamp. Had to sell them 120w
Watt Meiser lamps instead. About similar but won’t
play nice with the lamp they are used to if one is next to another. Lamp changing and or problems of playing nice with each other is very common. Can’t tell the difference between
HPL lamps to the best of my knowledge, and for the most part on real
ANSI lamps, you shouldn’t by the eye be able to tell much of a difference brand to brand but there are in the industry differences otherwise brand to brand in a lamp. Just how it is and what makes study into them interesting at times.
On full lots or un-opened cases of lamps, I buy say the
Mac 2K lamps in lots of 100 per month per year. I try hard not to - at least as much as possible not out lamps of the same lot on the same show if at all possible. This granted it’s often easier and without problems. Once in a while however you will get a bad batch and a case of ten while often the company itself mixes up what’s in a case to ensure you don’t get all a case as bad persay, you will run across a large big batch meaning you get an entire case of bad lamps that even if mixed up amongst the lot was still all bad. That would mean all the spare lamps or lamps sent out to prep fixtures with were bad as opposed to say one out of 20% spare lamps sent on the show. Much better as today when a show got 4x VL500D lamps bad (unknown reasons be it someone in getting the spare lamps before their show didn’t
mark the boxes as bad, lamps got dropped in bad packaging or bad lot of them), none the less they still in getting a few bad lamps still had a few more to use and only needed a re-supply of spares. This as opposed to searching out for local vendors that had the lamp available at extreme price given all the spare lamps were bad. Different lot numbers of lamp at least given one out of three reasons (above) this show wound up with bad spare lamps, at least got them two spare lamps that did work. IN sending them four more, one more lamp was bad in pulling it out of the cabinet. Broken
filament, not used but could have been dropped. Hard to tell on the bad packaging not sufficient to support the lamp in a
drop, verses bad lamp. Just a few $$bucks per lamp down the hole.
Still in my opinion, it’s best and most economical to try not to use the same lot of lamp unless in a perminant install installation where normal what is it 80% group replacement rates apply. And for that one hopes they don't die before they should or one's business manager might just have a hart attack with an un-expected expense.
Side notes on
bench focus and or one brand or another of moving light lamps. In the above
Mac 2K lamp examples, it was not that one brand didn't live up to its expected lamp life persay, or for the most part 2/3 of that expected lamp life as the norm lamp to lamp, only that the other brand normally lived up to 1/4 past its' expected lamp life over that which in well over 100 lamps - well over, I found to be fact for my instance. Thus now the test of the new lamp now out on a tour mentioned on this forum of the four prototype lamps.
Also, a concept of lamps in use other than in club or more or less perminant install. Some lamps go out on tour and those tours can last months or years - got a really really long tour out there for instance that has gone
thru hundreds of moving light lamps in the past year, or for instance a shorter production that paid for a total re-lamping at once. Two different options. For me on the other
hand it's more those fixtures that come off a long tour and by that time assuming what was a used lamp has already expired during the tour, some designer in the programming stages already rejected the lamps which after programming were not the same or by choice chose six at random say to replace
etc. This in addition to during the tour lamps replaced at any
point in the tour. You get a range of lamp life in lamps coming off the tour but for the most part after the tour the lamps mostly trash.
IN a total inventory, once off tour some fixtures will get turned around for a new tour in getting either re-lamped new or if looks good still in
bench focus amongst ten or thirty fixtures all on-line and focused together, they all look good or are optimized the same. Some won't stay that way but most do with varying hours just as some lots of lamp won't last as long as others no matter the brand - a how close to lunch type of thing at times I'm sure. Still that's the fixtures that got sent out on another tour along with new fixtures that with new
ballast will further complicate the matter of used lamps matching up with new lamps. Some fixtures won't be needed for the tour persay and will instead be turned around for say a corprate show or even tent show or what ever. Such fixtures than get teamed up with other of the type that didn't do the tour and instead just went out on say
one-off's for the last few months. Far different situations for the lamps in the fixtures by way of hours and
strike amounts. Each show gets all fixtures going out on it bench focussed next to the rest of the fixtures going out on the show. Doesn't matter the lamp life, each is matched to another after initial inspection and cleaning. Don't matter lamp hours once they all get optimized together, what don't match gets replaced. No buckets of "good" and "bad" lamps next to each other to re-lamp to given the show - all shows get good lamps or the lamps are replaced. All lamps are also tracked on computer to their life for
return value. None the less, further info on lamps in a touring situation in me having a
return factor of like 60K a year in bad lamps back to the manufacturers for bad lamps and some do or are because of bad lots of them. Better to mix up the lamps supplied to the fixtures in not getting a bad lot because it does happen and unless you are organized enough to tell lamp history sufficient to
send it back, you are better off both for lamps on
hand and ability to
cover for bad lots of them get them at random.