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In 1984, to get the amount of light put out by ~250-300 watts of LEDs in 2022 would have required the incandescent light array to come perilously close to the l
by jerf 5y ago
In 1984, to get the amount of light put out by ~250-300 watts of LEDs in 2022 would have required the incandescent light array to come perilously close to the limit of what it is safe to pull from a single outlet continuously in the US, which is 1500 watts. (You can transiently pull 1800 from a standard wall outlet, which is used by hair dryers, but you're not supposed to pull it continuously for hours at a time.) It also would have functioned as a full-on space heater (that was on continuously, not on a thermostat as needed), and very careful attention would need to be paid to cooling this massive array.
So, I'm gonna read between some lines here, but: I imagine earlier efforts would then by necessity have produced less light, because it's actually a lot easier to deal with ~400-500 watts of incandescent light than 1500 watts of incandescent light. 400-500 I think you could just about get away with putting a diffusion screen in front of them and making sure the enclosure has a lot of passive air flow. At 1500, if you're going to enclose this into a reasonably-sized product you're going to need active cooling with fans.
And there is a little noticed and rarely talked about weakness I've seen in several science fields where I've dug into a history of papers, which is that once one investigator picks the parameters of an investigation, it tends to "stick". If the first scientist investigating "Light therapy for SAD" and picked a 500 watt incandescent setup, it is extremely likely that many further papers will try to match their lumens setup, in the interests of trying to keep the papers informing each other. The entire therapy may live and die on the contingent conditions the first couple of researchers happened to pick, even after the entire lighting landscape has changed and it's practical to blast 5 times the light per watt and have time-varying light temperature now, which would have been even more difficult in 1984. (Conceivable, with some sort of rotating filter screen in front of it, but now you're cutting in to your light output even more, unlike modern LEDs which give you more options in dealing with this.)
- kragen 5y agoBy the 01980s you could have easily been using fluorescents, which went mainstream a quarter century earlier, so I think your stickiness hypothesis is the more likely problem. This had been puzzling me! Thank you for providing the likely solution!
- uxp100 5y agoMaybe fluorescents with the idea that the narrow spectrum of light produced was less likely to be effective?
- kragen 5y agoWell, I mean, SAD lightboxes do use fluorescents.
- Retric 5y agoI spoke to a physiatrist who considered full spectrum light to be essential in the light boxes. Don’t know about the actual research on the topic.
- ghostly_s 5y agoThe entire market of SAD lights was fluorescents pre-LEDs, they can be made just as "full spectrum" as LEDs are (by which I mean neither is capable of true full spectrum, just an approximation with appropriate phosphors).
- Retric 5y agoIncandescents can actually produce a continuous spectrum, so I am guess this is and was just misuse of the term.
- kragen 5y agoYeah, I assumed you were saying that the physiatrist was insisting on the use of incandescents for that reason. I don't know why someone would interpret you as saying that LEDs were superior to fluorescents, since obviously neither one produces full-spectrum light!