# Initial & Median Lumens?



## Big John (May 23, 2010)

I've got two types of 175 watt probe-start metal halide fixtures, one type takes a medium base lamp, the other type takes a mogul base lamp.

The medium base lamps very obviously cast a much brighter light, but the specs say they only have an initial output of 14k lumens and a mean output of 11.5k lumens.

The much dimmer mogul base say they put out 17.5k initial lumens and 13k mean lumens.

Any idea what explains the difference between the specs and reality?

-John


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## joethemechanic (Sep 21, 2011)

Big John said:


> I've got two types of 175 watt probe-start metal halide fixtures, one type takes a medium base lamp, the other type takes a mogul base lamp.
> 
> The medium base lamps very obviously cast a much brighter light, but the specs say they only have an initial output of 14k lumens and a mean output of 11.5k lumens.
> 
> ...


Different parts of the spectrum?


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## sparkybac (May 16, 2009)

It could very well be a difference in fixture type or reflector, rather than the lamp. Fixtures are sold in different types to allow different light "throw". Some fixtures are designed for a wide angle "throw", some with more of a close angle. The appearance of the lamp brightness would look different depending on the type of fixture and relative to where you are standing. That's my guess.


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## smiley (Sep 28, 2011)

*MH175 differences*

Are they both new lamps and ballasts? Some ballast don't drive the lamp at the same level. MH lamps loose up to 40% of their light output.
Some manufacturers produce their standard lamp at 3000K, others are 4100K.
the photometrics of the fixtures could also be different.


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## Big John (May 23, 2010)

The published wattage, CRI, color temp, and the life on these lamps are identical. The only thing different is the lumens.

I suppose it could be the reflectors, I hadn't considered that. The moguls are old fixtures, and the medium bases are brand new with nice shiny reflectors. It just seems like a lot of difference to attribute to reflectors.

I know Lightman was telling me that the "average life" number is pretty much BS, so I was wondering if maybe they were playing games with the lumens, too?

-John


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## CADPoint (Jul 5, 2007)

Big John said:


> I've got two types of 175 watt probe-start metal halide fixtures, one type takes a medium base lamp, the other type takes a mogul base lamp.
> 
> The medium base lamps very obviously cast a much brighter light, but the specs say they only have an initial output of 14k lumens and a mean output of 11.5k lumens.
> 
> ...


You really can study a lot of this yourself on the internet 

This is a layman's explaination!

The metal halide fixtures when it turns on or stikes, uses the outer leads that ignites to see viewable light but still works on to fire up all the gas inside a tube of gas.

Frankly one is sending a current through gas to heat up to a temp that will then let uses more power up all of the gas in tube to stablize to it's KV temp, if one watchs these bulbs fire up one will note the various Hue's of color(a spectrum of colors come across, example is MH street lights)

This is why you have a higher lumems it takes a lot more energy to fire up everything inside the lamp, and it settles down to a mean usage.

The terms of the follwing also come into play:
Mean, medium, mode = average, middle valve, valve that appears more times: respectifully.


In a nut shell
It takes a little more energy to stike the gas bulb and the gas is reacting to the energy. So there is a high input to ignite and then it settles down.

Diagrams of a metal halide bulb

Hue is more in respects to Kevin temp.
Lumens is a used a quantanty measure of foot candles.
One can read the comparison Here 

Hope that helps

PS
About 12 KV is about the average output 100 watt bulb and is lampshaded light, and to say base line white light (I know it wrong for me to say that) let me say mean light.

CFL's and now other light, application can average the same 12 KV lumen but way lower wattage usage. Above say 12 one is getting in Blue in CFL's and even 14 to 17 starts getting into hues of yellow with MH (stating from memory) It just depends on what material one is trying to excite!


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## sparkybac (May 16, 2009)

While CADpoint makes some good points and goes into great detail on the inner workings of lamps, I really don't think his explanation answers your question. I still think it's the reflector. 
Aside from the type of reflector being used in the fixture, another thing it could be is the lamp type, or envelope size, in relationship to what the fixture was designed for. There are at least two different sizes of MH lamps available in 175W w/ mogul base. An ED17 envelope and an ED23.5 envelope. The ED23.5 is bigger than the ED17. 
If the fixture (and reflector) was designed for the ED23.5 and you are using a ED17, then you will not get the full benefit of the design of the reflector and fixture. The ED17 would not sit up as high and fit in the "sweet spot" of the reflector that the lamp is supposed to. I have seen incorrect envelope size lamps used in exterior fixtures, and you can REALLY tell a difference when the correct lamp is installed.


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## Cletis (Aug 20, 2010)

*Lumen*

A lumen is only as good as what's absorbed by the eye grasshopper...


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## Lighting Retro (Aug 1, 2009)

Sounds like a superior design to the fixture. It's not uncommon for us to see a customer retrofit a 3 lamp parabolic troffer with 32W T8 lamps to a kit with (2) 38w T8 lamps and new reflectors.......


........and look better. Design has quite a bit to do with it. Engineers can be quite ingenious with some of their designs.


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