Conventional Fixtures Source4 Par lamp vs gel life

[rphilip]

Is gel life in Source 4 Par's more tied to the light output or the lamp wattage?

I'm in a situation where i've got a 750W lamped S4 par which is burning gel fast while a 575W/X (long life) is just fine (thought dim). I want to change out the lamps in both fixtures to match while staying as bright as I can.

I'm considering both the 750W long life and the 575W regular which have about the same light output, wondering which will have better gel life? All lamps are 115V, I've not measured the wall voltage under load.

Philip

(edit - clarify)

 

[tayklor]

To my understanding, power draw is also a direct measure of heat production. Regardless of the lamp's light output, at a given wattage it will dissipate the same amount of heat. A 575w lamp will output 575 Joules of heat per second, independent of the amount of light outputted. Gel life is more related to heat than light transmission.

 

[derekleffew]

Interesting conundrum. Even though the 750W LL is a lower color temperature and slightly less bright, I too would hypothesize that it would burn color faster. A color extender and heat shield would solve that, and might be needed on an S4-PAR MFL pointing straight up with R84 or L181, even with a 575W lamp.

Non-informative study attached.

View attachment 575vs750X.pdf

If power consumption or dimmer capacity is not an issue, I'd go with the HPL750/115X, since it costs the same or one or two dollars more, but lasts five times as long. For an educational institution. In a professional setting, you'll rarely see a long-life lamp, other than perhaps in an architectural installation.

 

[rochem]

Non-informative study attached.

Can you explain what we're looking at here? I looked over it briefly, but I confess that I'm not totally sure what it's telling me. From my quick glance, I don't see anything being calculated, just numbers being put into different orders. What am I missing?

 

[derekleffew]

It doesn't tell much of anything, hence the "Non-informative study attached." disclaimer. But I had already entered the data, so figured might as well post it, to confuse the innocent.

I originally made the workbook to study the effects of over- and under- voltage on lamps. Now if the OP could tell use what his socket voltage was, we might have a better clue.

 

[65535]

The useful info in that is to determine the amount of energy produced by the lamp in different spectrums. The 575W produces nearly the same visible luminous output as the 750W lamp. Knowing that to produce the same light that filaments must be hotter to produce a higher efficacy we also know the color spectrum will shift to a higher temperature.

With that insight we can also postulate that the spectrum of the 575W is shifted towards the UV end (more UV production) and the 750W is more towards the IR red (more IR production.)

Now since the 575W is producing more of the input energy in visible light and less in other ranges both IR and UV compared to the 750W lamp we have to determine wether the visible spectrum (which color filters affect the most) degrades color filters or if non visible spectrums do.

Having a higher efficacy the 575W lamp produces much less non visible light than a 750W lamp of the same luminous output therefore the 750W lamp will produce UV and substantial amounts of IR energy where as the 575W does much the same but lesser amounts and shifted towards the UV energy levels.

My general assumption is that due to the fact that 100% of the energy produced by the lamp ultimately is converted to heat (light and heat) that the more input power you have the faster you will degrade your color filters. Under that assumption the 575W is the way to go unless you have a very specific reason to use extra long life lamps. Gobos and other light absorbing accessories will also benefit from lower thermal absorption.

Another advantage to 575W lamps is the lower power requirements; that equates to lower instrument temperatures, longer life in all accessories in the instrument, lower heat into your venue, and the ability to use more instruments on a single dimmer for washes and other stage filling lighting uses.

The downside is lamps will burn out more often. Also check the color temperature difference in the lamps, I expect they are a few hundreds degrees different minimum.

Truth be told all this typing didn't scientifically prove that one lamp was superior in extending gel life.

 

[rphilip]

It doesn't tell much of anything, hence the "Non-informative study attached." disclaimer. But I had already entered the data, so figured might as well post it, to confuse the innocent.

I originally made the workbook to study the effects of over- and under- voltage on lamps. Now if the OP could tell use what his socket voltage was, we might have a better clue.

Well I measured the voltage at the socket with a 750W load today and it was 117V. However some time "soon" I'll be moving the light onto a different circuit run from a Unison rack which I expect will lower the voltage a bit.

Also Derick you guess of R84 in a MFL was not too far off, it's R90 and a VNSP, it is pointing nearly straight up. Interestingly R121 in the exact same situation was starting to crinkle after an hour and a half vs a 3" hole in the gel in under a half hour. I wonder if its a different substrate between these two gels.

I'm thinking that I'll switch out the 750 regular for a 575 regular and see how things go with on an extender and add that as needed.

Thanks,

Philip

 

[bdkdesigns]

I'm guessing this is a S4 PAR EA and not the MCM? Granted it was a 575w in an MCM: we had a ghosting problem before our renovations in our blackbox. We had a S4 PAR MCM left on at full overnight by accident in R382 (congo blue) and experienced no burnout or bleaching which really surprised me.

I take the fact that is a S4 PAR EA due to the fact that you are talking about using a 750w lamp. If it is a MCM (which stands for Metal Cold Mirror if I'm not mistaken), then it is a no brainer to switch to the 575w lamp because it is only rated up to 575. I know I've had to remove 750w lamps from them in the past because the bases are interchangeable.

 

[JChenault]

Putting on my practical hat for a moment ( a rarity for me as I love thinking about these kinds of theoretical issues) I would suggest that you might want to try some other color media. The longevity depends in part on manufacturer. Adding a gel extender and a heat shield, switching to another manufacturer might make more difference than the lamp you choose.

 

[icewolf08]

Well I measured the voltage at the socket with a 750W load today and it was 117V. However some time "soon" I'll be moving the light onto a different circuit run from a Unison rack which I expect will lower the voltage a bit.

Also Derick you guess of R84 in a MFL was not too far off, it's R90 and a VNSP, it is pointing nearly straight up. Interestingly R121 in the exact same situation was starting to crinkle after an hour and a half vs a 3" hole in the gel in under a half hour. I wonder if its a different substrate between these two gels.

I'm thinking that I'll switch out the 750 regular for a 575 regular and see how things go with on an extender and add that as needed.

Thanks,

Philip

First of all, you rbiggest problem is the fact that you are using the fixtures pointing "nearly straight up" and you are using a color with only 13% transmission. Pointing the fixture in a near straight up orientation means that you are sending the vast majority of the heat generated toards the color media. Odds are that if you tested the same color in a fixture pointing down, the color would last longer. Then you have to consider that 87% of the light is being absorbed/converted to heat by the gel, that is a lot.

You will probably see some improvement in gel life if you switch to a lower wattage lamp, but you will sacrifice luminous output. If this is a color and setup that you use often I would suggest that you invest in some dichroic color. It will cost more up front, but it will last way longer than standard color media (provided you don't drop it). If this is just a one-off event, and you will never use this particular setup again, then just buy a some extra color. It is not atypical to have to replace dark colors of the run of a show.

 

[WooferHound]

According to this
Gel color conversion Chart
http://upstagereview.org/Lighting Articles/Gel Conversion Chart.pdf

You could also try

Apollo - AP5400
Lee - 090
or
GAM - 650

 

[rphilip]

This is a bit of a weird event, it's once a week for ~2 but they rotate through the color used (green, blue, teal, ...)

They were back to green this week and I put 575W regular life lamps in the lights and the gel made it through but just barely. There were a few noticeably clear spots in the center after about 1.5-2 hours on.

I'll defiantly be considering gel extenders and moving back to 750W lamps as the extra brightness would be helpful.

Thanks

Philip

 

[icewolf08]

If you change colors regularly, I would suggest possibly investing in come scrollers with custom gel strings. If you were to buy a unit like the Apollo SmartColor, they come with Apollo Gel shield built in, and they have a fan that keeps the air moving between the fixture and the gel. You might actually see significantly longer gel life, and you would reduce the amount of time required to change gels. You could also use more colors more often.

 

[Kelite]

Apollo Design | Gel Shield - 6" x 6"


Perhaps teaming a color extender with an Apollo Gel Shield nearest the lens, with the gel filter farthest away from the lens. This will certainly extend the life of the darker transmissions exponentially!

Just a thought-