White LEDs

[AC/HL]

I'd guess that CFL development was chopped off at the knees by the rapid advance of LED technology. Whoever thought that up is probably working on the next step up.

[paulsherwin]

I'm not sure there was much phosphor or indeed other development with CFLs apart from miniaturisation. I have an early 2nd generation Philips 'jam jar' CFL still in use in one of my rooms, and both the light quality and warmup times are indistinguishable from later CFLs.

[high_vacuum_house]

I mourn the loss of SOX and MBF (high pressure mercury) street lanterns.

Since they changed the Thorn Beta 5 SOX lantern on a lamp post outside of our house to an LED unit, I have had to fit a solar light next to the front door so that I can find the right key for the front door!. Below the lantern is far too bright but move away from its centreline say 20-25 degrees and there is very little light dispersed. The street lighting in the road is almost a series of spots. I think that little optical research has been done for retrofitting existing lighting columns and more on maximum efficiency.

This is one reason why I fitted a nice 50's vintage street light with a proper 80W MBF lamp in the garden! I also installed a vintage 50's concrete swan neck lantern with a REVO rural open lantern fitted with a correct Derby pattern 100W lamp above the chicken house!! I prefer the light output from these lamps compared with LED lamps.

Christopher Capener

[G6Tanuki]

Originally Posted by AC/HL

I'd guess that CFL development was chopped off at the knees by the rapid advance of LED technology. Whoever thought that up is probably working on the next step up.

I'm still thinking that there was some sort of intrinsic low-level physical/optical constraint on what-could-be-achieved with CFLs. The CFL-manufacturers [and before them the old-style ballasted non-compact-fluorescent-tube-manufacturers] had decades of experience in the market - but they couldn't engineer a good, white, up-to-full-brightness-as-fast-as-a-filament-bulb solution - despite their market being heavily subsidized by various 'green' government-programs and tarriffs.

I don't weep for the demise of tallow 'rush-lights', whale-oil lamps, candles, gas-lights, carbon-arcs, old-style coiled-coil tungsten lamps, sodium- or mercury-lamps or fluorescents. LEDs have, in the last decade or so, made the old ways of generating light look utterly silly.

There's a nice study of the practical economics-of-lighting here: https://ourworldindata.org/light

[duncanlowe]

I remember the early days of CFLs. Initially I thought they would be great, and got a 'jamjar' philips. The big mistake was putting it in a room with low usage so it was only on for seconds or at the best minutes and the warm up time meant it was always massively dim compared to the TF lamp it replaced. The warm up element means my MiL is still completely opposed to CFLs.

But another point, where CFLs should be a good answer for lamps that are used for longer periods, I had bad experiences too. They may use less energy, but did not last anything like the period they claimed. I had many die 'young' and even a couple where the thing actually went bang.

LEDs have largely been better. Not universally (I've had undbranded and Osram fail at unreasonably short life) but overall I still think that value for money on purchase price and running cost, I'm favouring LEDs.

Regarding colour, there are very many whites. The colour temperature should give you an indication of what it will look like, the higher CT the 'brighter' white. Warm white is 'cooler' than daylight for example. For whatever reason, in identical fixtures, we have warm white at the back of the house, and cool white at the front. I have to remember to fit the right replacements when doing it.

Replacement LED's I hear you say? Well yes and it comes down to price / life. The ones we have outside are pennies cost ones (Home Bargains), but though they have the most use, are still probably best cost per hour by a long way. As I implied earlier, an expensive OSRAM was probably the shortest life we had.

[turretslug]

I wonder if CFLs were hobbled by restrictions on what could actually be used in the phosphors (is that the right term in this context?) to maximise efficiency/optimise colour rendering? Perhaps if they'd been introduced a couple of decades earlier they'd have had better performance but poorer environmental credentials. I recall as a kid that there was a bit of a flap on about removing fluorescent battens in squash courts in case a tube got broken and showered mercuric/whatever powder all over sweaty scalps. Or something like that.

Yes, they were sometimes short-lived and finding one whose colour rendering was anywhere near pleasant was unusual. I suspect that there was a lot of marketing pressure to make the electronic gubbins bit and its housing smaller than was wise and everything cooked up. Still, they were a source of compact HV transistors capable of several watts dissipation if you could be bothered.

LEDs are very impressive, both from the efficiency and appearance- as an experiment, I populated a triple "candle" type ceiling lamp with one each of conventional tungsten, tungsten halogen and LED "filament string" bulbs. If you're nerdy enough, you can spot which is which cold, but switched on, the similarity is very good- and I'm quite picky about colour rendering. One consumes about a tenth the power of the others, though!

[dave cox]

Flourescent lamp phosphors

[emeritus]

I have a couple of UV CFL lamps that I got from Mapln some years ago. Presumably they are essentially CFL lamps without phosphors but with a black lacquer coating to block visible light. I mostly use them for curing the old-type Loctite glass adhesive of which I still have several tubes, and have also used them for completely removing the yellow from my Pentax Super Takumar lens whose radioactive glass element discolours the lens cement of one of its cemented doublets. They really used to make the green screen of my old Amstrad PCW's monitor glow brightly from more than 2 metres away. Haven't found any other use for them, although I believe UV light can be used to detect refrigerant leaks in certain air conditioning systems.

[Superscope]

Ref: Post #25

Somebody has obviously forgot to tell OSRAM
that they are not supposed to still be taking
part in the Light Bulb Conspiracy




Ian

[emeritus]

When we had a mid-week break at Warners last year, the LED bulbs in our bedside lamps lasted on average about 20 minutes: three bulbs in three days. The lamps didn't have mechanical switches, but operated by touch, and on closer examination of the underside labelling, had electronic dimmers. Not that the dimmer had much effect in the bulbs' illumination: I had initially thought that the reason it took several taps to turn a lamp off was due to problems sith the touch switch. On the 4th day I pointed out to the maintenance guy that the bulbs he was using (supplied by site management) were specifically labelled with a warning that they were not suitable for use with dimmers. He did manage to find a LED replacement that was dimmer-compatible, and, unlike the previous ones, this did change its light output in steps in response to succesive taps on the lamp base, and was still working the next day!

[AC/HL]

Please try to keep vaguely to the topic as posed by the thread title.

[ValvoStef]

with reference to emeritus, another question has come to mind: does the sectrum change with the intensity of LED light, i.e. a dimmable LED?

[duncanlowe]

I've not noticed any colour change with dimmable LEDs, several of which we have in our lounge. 6 in wall lamps, and three in the main fitting.

[Jon_G4MDC]

Isn't dimming of LEDs done by variable duty cycle?
That should keep constant colour but mind the strobe and flicker effects.

[G6Tanuki]

Originally Posted by ValvoStef

with reference to emeritus, another question has come to mind: does the sectrum change with the intensity of LED light, i.e. a dimmable LED?

There are "non-spectrally-compromising dimmable" LED-lamps, along with some "dimmable" ones which also change their colour-spectrum to a 'warmer' [i.e. more-yellow-so-people-look-like-they-have-terminal-jaundice] spectrum when dimmed.

For example: https://www.lighting.philips.co.uk/c...-bulb/warmglow

[Personally, I'll always choose the whitest-of-white spectrum; I don't want to be reminded of 1970s power-cuts and living-by-candlelight]

[paulsherwin]

The subjective colour temperature may change somewhat as the light output falls.

[turretslug]

Originally Posted by dave cox

Flourescent lamp phosphors

That made for an interesting read on the historical background- but if only the author realised that over-earnest sales-pitch spiel about anything, particularly lamp phosphors, being "exciting", "creating an enhanced sense of well being", "astonishing" and so on is a turn-off for many, not to mention casting doubts in the reader's mind as to objectivity.

[chris.oates]

On the subject of the OP I discovered the blue/yellow spectrum of a basic white led when I used a white led to replace an incandescent bulb behind a red indicator lens. It didn’t illuminate. Clearly the answer was to use a red led.

Chris

[Andrew2]

Originally Posted by Hartley118

Street lighting lanterns had reached a high degree of sophistication with low pressure sodium lighting, giving a remarkable uniformity of illumination of the road with their careful prismatic design. Personally, I find the orange monochrome light less glaring than white light, particularly on a wet night. Maybe it's something to do with reduced dispersion where a greasy windscreen film is involved.

When LED lighting came along, it seemed that all the design archives of optimum optical design of lanterns had been sent to the skip and an entirely new team of naive optical engineers had to learn how to do it all over again. For example, we used to have a sodium light at the end of our drive: its good lateral light distribution easily illuminated the way to the house. Now that it's been replaced by a new white light, the pedestrian has to grope in darkness once they've left the pool of light immediately under the lantern.

That's interesting. The street lamps around here were replaced with LED types a couple of years ago and I find them a significant improvement over the old sodiums. The diffusion is better, there being very little 'pooling' effect. The light quality is similar to bright moonlight, very pleasant. They look like this:

[Refugee]

They did our street lights a couple of years ago.
They are smaller being in a residential area.
They are also wildlife friendly
I can remember sodium ones with an awful light spread in the 1980s.