Author Topic: Strange halide chemistry in my Aliexpress 5000K 70W MH lamp  (Read 631 times)
dor123
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Strange halide chemistry in my Aliexpress 5000K 70W MH lamp « on: July 28, 2025, 08:48:48 AM » Author: dor123
I bought this 5000K 70W MH lamp from aliexpress.
Expecting it to have Dy-Tl-Cs, here is the actual spectrum of that lamp: https://www.lighting-gallery.net/gallery/displayimage.php?pos=-258376
Having around 5000K light color, the lamp seems to have Na-Sc-Dy-Tl instead of Dy-Tl-Cs.
Why?
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Re: Strange halide chemistry in my Aliexpress 5000K 70W MH lamp « Reply #1 on: July 30, 2025, 10:07:05 AM » Author: dor123
@RRK, @James, @Medved?
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Re: Strange halide chemistry in my Aliexpress 5000K 70W MH lamp « Reply #2 on: July 30, 2025, 02:45:57 PM » Author: Medved
Because the maker choose so...
Could be raw material availability (at the given factory, with the given machinery), could be targeting certain specific parameters for some reason, could be using old remaining material inventory because someone found some old stash for cheap,...
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Re: Strange halide chemistry in my Aliexpress 5000K 70W MH lamp « Reply #3 on: July 30, 2025, 03:12:09 PM » Author: James
I could ask why you chose to eat what you did today - each maker has choices, and there are so many ways to achieve a similar end result. Every company tends to have its own preferred recipe of ingredients, there are no fixed rules.
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Re: Strange halide chemistry in my Aliexpress 5000K 70W MH lamp « Reply #4 on: July 31, 2025, 09:27:32 AM » Author: dor123
But this halide chemistry is very unusual. I've never seen a daylight MH lamps with Na-Sc-Tl-Dy, but only with Dy-Tl-Cs, Dy-Cs and Dy-In-Tl-Na.
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Re: Strange halide chemistry in my Aliexpress 5000K 70W MH lamp « Reply #5 on: July 31, 2025, 09:46:57 AM » Author: dudam001
It’s up to the makers, Dor
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Re: Strange halide chemistry in my Aliexpress 5000K 70W MH lamp « Reply #6 on: July 31, 2025, 05:16:16 PM » Author: James
There are many more recipes than just those for daylight MH - very frequently with some or all of the dysprosium replaced by Holmium and/or thulium.  Also with additions of hafnium to improve the continuum and CRI.  But these details are extremely difficult to identify even with a high resolution spectrometer.  Terbium-caesium is not too uncommon, along with various gadolinium / yttrium / neodymium based fills but again very difficult to identify these from the spectra due to the very large number of spectral lines.
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Re: Strange halide chemistry in my Aliexpress 5000K 70W MH lamp « Reply #7 on: August 03, 2025, 02:35:33 AM » Author: Alex
There is also the problem that just because you, I or James hasn't seen something does not mean it is unusually...
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Re: Strange halide chemistry in my Aliexpress 5000K 70W MH lamp « Reply #8 on: August 03, 2025, 12:22:55 PM » Author: RRK
Sylvania's 35W quartz metal halides with integrated reflectors, included dichroic colored versions, are using this chemistry, rare earth + NaSc. It was discussed on L-G a couple of years ago. So not that rare or strange. I think one of my Chinese 70W MH lamp with ~6K color used this mix, too.
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Re: Strange halide chemistry in my Aliexpress 5000K 70W MH lamp « Reply #9 on: Today at 09:50:18 AM » Author: dor123
I think that the said Sylvania 35W MR16 QMH lamp, is I think 3000K color and designed to have the same color stability like CMH lamp, to dispense of the outer jacket, so the arctube would burn in free air.
Is there any advantages of using Na-Sc-Dy-Tl chemistry in daylight MH lamps? Beside the very small additions of Dy and Tl in my lamp, the CRI is poor compared to daylight lamps with Dy-Tl-Cs or Dy-Cs or other rare-earths.
Because of this, I've asked once, why Osram changed the halide chemistry of its HQI-TS/D from Dy-Tl-Cs to Dy-In-Tl-Na.
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Re: Strange halide chemistry in my Aliexpress 5000K 70W MH lamp « Reply #10 on: Today at 04:46:30 PM » Author: RRK
In my experience, Dy + Tl lamps almost always have some hateful residual green tint and some unpleasant metamerism due to a narrow green line, even when made by Iwasaki! So In + Tl + Dy + Na seems to be a better white color at least to my eyes.



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