dor123
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| Why CMH lamps were only made between 2800-4500K and not higher CCT?
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I"m don't speak English well, and rely on online translating to write in this site.
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I lives in Israel, which is a 220-240V, 50hz country.
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dor123
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.
I only working with the international date format (dd.mm.yyyy).
I lives in Israel, which is a 220-240V, 50hz country.
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James
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| There would be no point. Even at 4000K it was kind of borderline as to whether or not CMH makes sense. The primary advantage of ceramic arc tubes is to run with higher wall temperature, so as to vaporise more of the sodium iodide into the plasma and attain lower colour temperature (NaI has very low vapour pressure and is difficult to get enough of it into the arc). However the other salts that produce higher colour temperatures have much higher vapour pressures and even at the colder wall temperature of quartz, there is more than enough vapour produced. Conclusion, raising the wall temperature of a high CCT metal halide lamp does not deliver a benefit in efficacy or colour and only causes a decrease in life due to faster corrosion reactions - or requires use of far more expensive ceramic arc tubes than the cheap quartz designs. So there was no real commercial incentive to develop high CCT CMH lamps.
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dor123
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| So what is the advantage of higher loadings and temperatures of the rare-earths in short-arc MH lamps?
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« Last Edit: September 07, 2024, 02:26:07 AM by dor123 »
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James
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| The main advantages are the shorter arc gap for greater optical precision, and under some circumstances a slight increase in red ratio. The luminous efficacy and even CRI can even be lower, and the life is very greatly reduced. This is one of the reasons why many daylight metal halide arc tubes are physically larger than warm white types.
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dor123
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| Some 942 colour CMH lamps, have the NaI being replaced by LiI (Like in the case of Philips CDM Lightboost 942 colour). Why is that.
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.
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I lives in Israel, which is a 220-240V, 50hz country.
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RRK
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| In fact, Iwasaki offered 5500K ceramic MH lamp. See a screenshot from 2008 catalogue.
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RRK
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| Full catalogue page on these lamps:
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dor123
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.
I only working with the international date format (dd.mm.yyyy).
I lives in Israel, which is a 220-240V, 50hz country.
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RRK
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| Sodium emits in yellow-orange area, sure. So lamps using sodium additive have some excessive orange light causing them to get poor R9 CRI score, because of orange/deep red imbalance. If a lamp designer can manage to get a target CCT without sodium addition, he is just happy to dispose of it.
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« Last Edit: September 10, 2024, 02:03:16 AM by RRK »
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Medved
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| I don't think the 4000K has not that much benefit from CMH at all. It depends what is more important for the application, whether just total cost per lumenhour (so quartz wins), or the need for better color rendering (mainly the saturated reds) where the CMH wins.
With higher CCT the difference may get smesred even further (quartz get better color rendering, as well as efficacy), so higher CMH cost won't get justified.
But the "higher cost", as well as "justified" ade very relative terms.
First "CMH" is marketing wise way more "sexier technology", so many, mainly less expert, customers are still willing to spend the premium for it, even if it is not technically founded at all.
Second aspect could be a manufacturer selling just few 5000+K lamps but tons of 3000 and 4000K. Then it does not make much sense to maintain dedicated QMH production machinery for the small volume of the high CCT niche and just design them also as CMH and share the machinery with the lower-CCT CMH mainstream. Of couse, some makers solve this by sourcing niche types externally. But for some brands (mainly those asking premium for being "better than others", e.g. Iwasaki) that may by unacceptable, but also they need to keep the range complete. When already asking higher prices, there is more headroom to use even seemingly not that optimal technology, or even selling those at slight loss just to maintain the product line complete.
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No more selfballasted c***
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