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Guess I don't see your point. If you use a blue light, don't you need the yellow filter? And why would you need a dedicated blue light when you can just add a blue filter when you wanted to see the fluroscence? I didn't find it something I would want to spend every night dive looking at. It was more a one time, "so that's what it's like - cool" thing. I found the night marine life much more interesting.
The reason why a dedicated blue light is generally better than a white light is with a blue filter is mainly the available output power in a the desired wavelength. E.g. if you start with blue and white LEDs with an output power of "10", the white LED will only deliver a fraction of that after the blue excitation filter is installed. For both approached you would need of course a yellow filter in front of your eye/camera to block the excitation wavelength (blue in this case).
 
The reason why a dedicated blue light is generally better than a white light is with a blue filter is mainly the available output power in a the desired wavelength. E.g. if you start with blue and white LEDs with an output power of "10", the white LED will only deliver a fraction of that after the blue excitation filter is installed. For both approached you would need of course a yellow filter in front of your eye/camera to block the excitation wavelength (blue in this case).

Thanks for the explanation. Makes perfect sense.
 
However, these scare the crap out of me:


Seems like a real bad idea as advertised but I have never seen one in person. Looks like it could be modified to install a reg and comms. Lose the snorkel part and vent air from the top of the mask. Making a poor mans band mask.
 
The reason why a dedicated blue light is generally better than a white light is with a blue filter is mainly the available output power in a the desired wavelength. E.g. if you start with blue and white LEDs with an output power of "10", the white LED will only deliver a fraction of that after the blue excitation filter is installed. For both approached you would need of course a yellow filter in front of your eye/camera to block the excitation wavelength (blue in this case).
I was told by Charlie Mazel, the man behind NightSea, that LEDs are fundamentally UV to begin with, and must have a phosphor on them to allow that white light....that is, the phosphor is excited by the LED light and emits white. So to make a UV (or approximately so) light, you need only to eliminate or change the phosphor...thus it is "brighter". I think I have the facts straight here, and am sure I'll be corrected if they are not!
 
I was told by Charlie Mazel, the man behind NightSea, that LEDs are fundamentally UV to begin with, and must have a phosphor on them to allow that white light....that is, the phosphor is excited by the LED light and emits white. So to make a UV (or approximately so) light, you need only to eliminate or change the phosphor...thus it is "brighter". I think I have the facts straight here, and am sure I'll be corrected if they are not!
The blue LED was made possible by creating a high energy gap pn-junction using InGaN. It was not made by “just eliminating” some internal Phosphor layer. In either case, I am not sure what your point is.
 
I was told by Charlie Mazel, the man behind NightSea, that LEDs are fundamentally UV to begin with, and must have a phosphor on them to allow that white light....that is, the phosphor is excited by the LED light and emits white. So to make a UV (or approximately so) light, you need only to eliminate or change the phosphor...thus it is "brighter". I think I have the facts straight here, and am sure I'll be corrected if they are not!

Errrrr... kinda yes, but also no.

Colour LED's (red, green, blue etc) are the colour they are due to the material the emitter is made from and they emit moncromatic light (unlike a tungsten light source with a filter, LED's are only producing a pure narrow frequency of light). This is why RGB LED lights make people look weird, they don't actually include any yellow light (if you want good colour rendition and colour mixing you need RGBA, or Red Green Blue and Amber). Non-UV LED's emit zero UV.

White LED's are basically what you describe, they are actually a blue (not UV!) LED with a yellow phosphor slapped on top. That phosphor absorbs the blue light and re-emits it as enough of a spread across the spectrum that you get a good enough approximation of white light. If you look at the graph of output vs frequency of a white LED you'll see that it has a big spike in blue and a broad hump across yellowish.

UV LED's are less common, for a whole bunch of reasons. Like the fact that the UV light actually degrades the plastic the diode is housed within, so they have a much shorter service life. Plus UV applications often require very high output, but high intensity UV point-sources (like LED's) are quite hazardous. So diffuse sources are preferred.

White LED's are less efficient than other types, partly due to the phosphor losses, partly due to the way we perceive and measure light.

To the original point, yes, 10W of blue LED will always be much brighter than 10W of white LED with a filter. Filtering LED's is generally not done at all, as its very in-efficient and typically produces poor results (due to the output spectrum of white LED's).

Blue LED light is no substitute for a UV source though. It will produce some interesting effects due to its monochromatic spectrum, but it will not produce fluorescence.
 
Miniature Ascent Rate Alarm - great idea if you could hear the alarm. Since you can't - totally dumb.
My dive old computer had a audible alarms. I had no idea for about 5 years. I never dive with my hearing aids. My buddies never mentioned it.
 
ide recon their chances of being found are 10000x better at the surface than they would be 60' under water.....even if it is just a body recovery at that point.

frankly ide just be worried about it malfunctioning and blasting me to the surface unintentionally.

ive not seen any statistics on how many divers die underwater by not being able to consciously make it to the surface...but doing some quick googling lead me to this:

Diving fatality data published in Diving Medicine for Scuba Divers (2015)[3]

  • 90% died with their weight belt on.
  • 86% were alone when they died (either diving solo or separated from their buddy).
  • 50% did not inflate their buoyancy compensator.
  • 25% first got into difficulty on the surface
  • 50% died on the surface.
  • 10% were under training when they died.
  • 10% had been advised that they were medically unfit to dive.
  • 5% were cave diving.
  • 1% of rescuers died.
DAN was notified of 127 recreational scuba deaths during 2015. 67 were actively investigated by DAN[10]

so if 25% first got into distress on the surface, that means 96 divers were in trouble underwater......and if 50% of them died on the surface, then 48 died underwater......

so this device would have potentially saved around 30-70 people annually....


in a sport where the fatality rate is 1.8 per million recreational dives.....it honestly seems like a greater liability than anything else.
What these statistics don’t show are the numbers of divers that dropped weights and survived. When a dive goes sideways and a diver makes it to the surface and drops his weights or tries to make a buoyant ascent, there a no statistical data to work off of. This corpse retrieval device seems more dangerous than any significant benefit.
 
https://www.shearwater.com/products/teric/

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