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George, Mark: Actually, you're both right. You're both talking about aspects of the same things. Energy goes into the bulb as electricity. It comes out as photons (light). In the case of the tungsten bulb, most of the photons are coming out at long wavelengths (infrared) (better known as heat). In the case of the HID lamp, the photons are almost all coming out in visible wavelengths. Color temperature is a single figure of merit that talks about the distribution of the wavelengths of the photons emitted by a black body radiator. Lower color temperature indicates that the photons are mostly distributed toward the longer wavelength (red) (heat) end of the spectrum. Higher color temperature indicates that the photons are mostly distributed toward the shorter wavelength (blue) (UV) end of the spectrum. Black body color temperature is a good way to describe incandescent and arc lights. It is worthless for fluorescent technologies, that put out a relatively small assortment of very discrete wavelengths. The eye (and visual cortex) responds to the discrete spectrum and decides that the composite result is white, but it isn't, not really. This is why things look "interesting" under, for example, Cool White fluorescents. Color temperature is also worthless for describing things like LEDs and lasers, but those technologies aren't usually used for cave lights. George is absolutely correct when he says that blue light penetrates water more effectively than red light. The Navy was doing some experimenting a while back using lasers to communicate with submerged submarines: they used blue-green argon lasers for precisely that reason. Mark, the problem with putting a filter on the light is that it wastes the photons (and hence the energy that went into the bulb to produce those photons) that are not at the wavelengths passed by the filter. So you'd basically throw away the 80% of the tungsten light that isn't useful anyway. >No, it is not. I said, in case you do not get it, that the light >penetrates the water better due to its high frequency, and that is all >there is to it. It also arcs rather than using a filament, so more of >the energy is light , not heat. This is why I really hate to even >discuss anything on these lists. My inclination is to tell you to go >show me how its done, and actually, I think I will. You go figure it >out, and then let us all know the real story. Been there , done that , >you have not and you don't have a single freaking piece of dive gear >that I would use to wipe my ass with, but you have all the answers. > >You go ahead an keep assuming I am an idiot, it seems to work well for >most other divers out there, and makes them feel better. I'll keep doing >what I do. > >Mark Melendez wrote: >> >> At 07:06 AM 7/25/99 , kirvine@sa*.ne* wrote: >> >> 18 watts. The reason I used the "..." for terms like >> "bright" is that we >> are talking the "effect" that we call "light" in water, >> chief. I just >> explained what is really going on, and that is the reason >> you can "see" >> further and "think" the light is brighter. The rest is >> horsehit. >> >> Also know that they are putting most of their energy out in >> the form of >> light, not heat, so you can turn them on out of the water >> without >> worrying about meltdown. >> >> Just for the sake of argument... The big reason that you've got more >> light chief is because you have an 18 watt HID bulb that's putting out >> the same amount of light as a 100 watt tungsten bulb - 80% of its >> energy becomes light, the opposite is true of tungsten. Not so much >> because you've got a higher color temp but because you've got more >> brightness. If color temp was the only factor you could simply put a >> dichroic or CTB filter on a quartz lamp to achieve the same effect. >> >> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> Mark Melendez >> melendez at bigfoot dot com >> http://www.bigfoot.com/~melendez -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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