Ultralume looks like some early kind of tri-phospjor rare-earth lamp judging by its spectrum??

@RRK Thanks a lot, this is very interesting!

I have heard of electron cooling in connection with some types of vacuum tubes, where you have to add power to the heater above a
certain power level. But I have never considered this in fluorescent lamps. Some years ago I have noticed that MV lamps turn black
more quickly at the electrodes when they are operated at too low a power. Could this be the same effect?

IMO, unlikely for HPM. For dimmed fluorescents, you have constant extra heating applied to the electrodes, no such luxury for HPM. So, the heat applied to the electrodes just reduces proportionally to in-between of 1-st and second order of lamp current. At some point, electrodes become too cold to keep enough electron emission and cathode drop starts to increase, increasing ion speed and cathode sputtering. Also, at some point of current reduction the arc will probably migrate to the starting coil parts of the electrodes back from the tips, increasing sputtering too.

The real thing, Halophosphate fluorescents

Possibly in 8W size ?

Failing that, maybe a higher CRI tube in an old luminaire which cover was discolored by UV (have no idea what the exact transmission spectrum of that would be, but assuming it it got green-yellow then it would cut down somewhat on the red and blue ends of the spectrum)

I would like to find something to match the 4100K halophosphate fluorescents. Yes, I know quite low CRI, not much saturated red, but not that much blue either, slightly greenish...

At lower lighting levels it evokes in me soothing late summer evening, at least like a single F15T8 in a corner for a whole living room does... :-)
Or the color of 3600K DX MV's.

High beam for cars should be banned!, it’s just allows people to drive faster at night! 🤨

5000K or (less commonly available) 6500K. Occasionally, the more recently developed 2200K.

to add to the above

My car uses the same setup with H4 lamps (fairly standard in European cars)

When i am in low beam and suddenly do need the extra light (when i see in the dark in the distance something that might be obstruction on the road) i just hold the handle in the "flash" position untill i pass the place of question (just before the point where it clicks to the "high" position and turns the low beams off). The 10 or 20 seconds won't do anything

If held in this position permanently, for one this would probably melt the headlight reflectors, which in most modern cars are made of nickel plated plastic. In some cars it melts already with the normal setup. (Once it started melting, the plating cracks and bad spot starts absorbing more IR and will keep melting)

Not good idea at all...

The headlight assembly is limited by its design on how much heat it can handle to the power of the one single filament at a time. So by powering both at the same time you get almost double the heat power the thing is designed for, so it will be overheating, damaging not only the bulb itself (the seals and the internal bulb, as I'm guessing it is a halogen, will be exposed to higher temperatures than designed for), but also its holder and the things around.
It may not be immediate damage, but over time it may lead to plastic parts becoming way too brittle and fall apart, paint pealing of the metal and the metal then corroding, sockets and wire insulation becoming brittle, crumbling away and leading to wires becoming bare and prone to short circuits and corrosion...


Cars which use separate headlamp for low and separate for high beam (like the ones using H7 or so) usually keep the low beam ON when the high beam is turned ON, the high beam optics is then designed to complement the low beam, so to throw the light only where the low beam is dark, so reaching higher total light levels. But these cars are designed with this, so the temperature management design of the headlamp assemblies includes this operation.


The combined headlights, like dual filament sealed beam or H4 can not handle the heat and need the low beam to be shut down when the High beam is turned ON.
Only the "warning flash" (aka "light horn") function (when you flash the high beam by pulling the control stick) allows to turn ON both at the same time, but then it is expected to last for just few seconds, so not enough time for the thing to warm up above the design temperatures.

I have two trucks with sealed beam headlights and both of them use either the high or low beams, never both. If I modified them to use both, would anything break?

Yeah I saw those equations, I don't know what half those symbols mean lol. I definitely learned from that.