HID vs LED for night diving

[scububa]

I completely disagree that the LED is superior in every way. I do agree that they have a lot of great attributes and in many cases, they are a logical choice. I also agree that they are getting closer and closer to meeting all the attributes of the HID, but they aren't there yet. So, HID still has merit. Every tool has trade offs and anyone that ignores that is being silly.

The other thing that drives me nuts is all the touting that an LED will last for ever. Everyone is quick to quote the MTBF (mean time between failure) or average life of the LED diode element. And, those numbers are indeed huge relative to other light sources. But, that is only one element in the system and comparing that to an HID bulb is also silly. The LED requires, again relatively, a complex drive circuit to make it work. And, the MTBF of the LED is only valid if the drive is well within set parameters including getting the heat out of it. And, this applies to the complete chain in the drive circuit. Just because the light is underwater doesn't solve the problem. The design has to provide a path to get rid of the heat. LED/driver systems should be compared to HID/Ballast systems. I know must people understand this, but all I ever see is the LED has 50,000 hours (that's six years of burn time or about 32 years of diving 5x/week at 2x/day at 3hr/dive).

I think LED lights are great and well done ones are a great solution. I have dove Dive Rite, Green Force and Light Monkey. But I'd like to see some better practical estimates of the reliability of them. My dive lights have been pretty good, but my land LEDs haven't been so great. I suspect switch issues in some and battery connection in others, but even a nice Sub Gear light has given me erratic performance. And, I have had failures in various LEDs for cabinets, closets, aquariums, etc. I didn't have any failure analysis done, so I don't kown if they were LED or drive or switch, etc. I GUESS that they are related to overheating, but they might be cheap components or other design flaws beyond heatsinking.

Okay, I settled down, rant off

 

[scubastingray]

I completely disagree that the LED is superior in every way. I do agree that they have a lot of great attributes and in many cases, they are a logical choice. I also agree that they are getting closer and closer to meeting all the attributes of the HID, but they aren't there yet. So, HID still has merit. Every tool has trade offs and anyone that ignores that is being silly.

What are LED's inferior at?
Also, every tool having trade offs is sort of laughable. Technology gets old.

Do you still use an abacus instead of a calculator? Carbs on your car instead of fuel injection?
That premise is great in theory, but doesn't pan out.

 

[Diver0001]

Hopefully someone will start making inexpensive light head upgrades for the older HID lights out there.

Greenforce already is for their own line of lights.

I don't know anybody who would buy a new HID light. I know some (I'm one of them) who still dives with HID but it will be replaced with LED when the time comes.

R..

 

[MRTdiver]

What are LED's inferior at?
Also, every tool having trade offs is sort of laughable. Technology gets old.

Do you still use an abacus instead of a calculator? Carbs on your car instead of fuel injection?
That premise is great in theory, but doesn't pan out.

here we go

 

[ben_wilson3301]

So I've heard some decent arguments for LED, but not for a particular LED. I guess if I go LED I would prefer a single bulb for signaling. Also a fairly tight beam. I would like to keep it under $1,000 US.



I has to have a decent halo though, I dont want to dive a lazer beam.

 

[Dive-aholic]

Single bulb is not necessary for tight beam. Watch the video I posted in #17. The 3000-S3 has 3 bulbs. The 4500 has 9. They both have decent spill. The 1500, which is not in that video, also has 3 bulbs and can be had for about $700.

 

[skankpile]

I prefer a quality HID because I want a useful light. Everything has a purpose, but a light that blasts low CRI is worthless to me. I cannot stand poor LED light and avoid it like the plague. I have custom flashlights made with high CRI so I'll have usable light. With a good HID or high CRI led you can look at an object and immediately tell what is growing on it, its health, level and type of soot, oxidation, better judge age, mineral type.. blah blah blah. A crappy LED just blasts out annoying high kelvin unusable light.

If you want to actually see the beauty of the world then buy a quality HID or high CRI led.. I prefer HID as things look more real to me instead of a washed out low contrast picture.

 

[Dhboner]

I have an LED can light and my son has an HID can light. His HID light has much more "punch" in low vis situations. In all other situations (including night diving) I don't think there is much advantage to HID anymore. HID lights are more expensive and much more fragile but if you do a lot of diving in low vis situations I believe they are still ahead of LED's.

 

[eelnoraa]

At this point, I have LM 21W HID and Hollis 25 LED. My LM21 HID is 3+ years old, so I would say it is not as bright as it was new. In monterey water, I still think my HID has edge over Hollis 25. HID beam is like a thick light saber, thick and doesn't spread much at distant. LED has smaller hot spot in close distant, but light spread out quicker as distand increase. The hot spot of HID is so considerable brighter. It is defiitely better light for signaling. Having that said, I think LED is a better overall light. If I can only have one, I will stick with LED and willing to sacrifies a little performance.

Now for night dive, I would say any canister light is just over kill especially in clear water. Too many time, I started a night dive with canister and only found my eyes were strained by the amount of light output. Then switch to a DRIS 1000 type of back up light to finish the dive. Very bright/strong light is for day dive. For night dive, you don't need to go crazy.

 

[Diving Dubai]

PEDANT WARNING!


Okay first off I need to get something off my chest. Bulbs get planted in the soil from which flowers grow!

With tungsten lights you have filaments, with HID you have electrodes, and with LED you have and array! - For heavens sake people will be using the term flippers and goggles next [/end pedantic rant]

So some explanations - this is my area of expertise for my day job

Firstly the use of a video is a bad example as your eyes are very subjective. I'll explain why in in a bit. The true measurement of light output can only be made with a light meter (either in lumens or lux) generally this measurement is made at 1 meter. Also light is affected by the inverse square law, thus if you double the distance you decrease the output by four. For example if you take a measurement of 100 lux at 1 meter, at 2 meters you'll only have 25 lux. Conversely at 0.5 meters you'll have 400 lux.

Next. the colour of light is measured in degrees kelvin. Tungsten is 3200 - 3400, HiD is around 5600 and LED 5600 - 7000. - What does that mean?

A tungsten light is a warm white (because it has a lot of red in it - and lots of infra red) HID is a bright white with a hue of blue (very much like daylight) and LED is a little bit bluer then HID (simplistically speaking.)

If you were to view a tungsten source and an HID source you would probably say the HID is brighter. Even if you found them to be the same on a light meter. This is because it is whiter AND it's spectrum peaks in similar places to the receptors of your eyes. Tungsten almost perfectly matches the spectrum of your eye receptors especially with Red and yellow - hence it feels a warm natural light in the home.

The natural spectrum of an LED is almost opposite to with its output to your eyes so to make it work you need to do some clever tricks.

Colour spectrums are important too. Tungsten puts out a lot of red but little blue, HID has loads of output in the blue end of the spectrum but little in the red. LED's have to be tinkered with to get the best output - but this can be tuned.

Also take into consideration the beam angle and field angle - the beam angle is obviously the maximum (or min and max) beam of a light the field angle is the angle of the beam where the light is bright and even before it drops off - Sine your light at a wall and you'll see a hot area (field angle) and the entire area of light is the field angle. Some manufactures measure the output just on the field, some across the beam, some both - few will tell you which! So not all quoted light outputs are the same!

LED arrays do last for about 25000 hours, but the degrade faster then that, however their degradation is still slower then HID and tungsten just fails quickly! LED also need heat management - hence some lights have a heat sink exposed to the water to get rid of the immense heat of the array

Optics. With HID and Tungsten its pretty easy just a concave reflector. with LED it is complex, indeed nearer to witch craft then to physics. If you put a decent LED torch near a surface your see a figure of 8 with two hotspots if you move it away you'll see the beam elongate to an oval, move it further still and the beam will become round...

So which is best?

If you want natural colours underwater then a tungsten will replace the red which the first colour lost better than the others - its also the cheapest, but size for size offers the least power output.

HID is great if you want a long range light, it has immense power to size ratio, but has a power appetite to match it. In TV a 2000W HID has the same light output of a 180W LED fixture.

LED obviously has lower power, lower maintenance costs - better array life and can be tuned to give an acceptable colour spectrum reflector and optics are complex to design hence lower price models can have a lower output even though they use the same array (array manufactures are limited in numbers)

Generally LED in a dive light is better suited to Video lights and recreational diving if you are a cave diver and want a long beam underwater then HID is still the way to go - however as signal light on the surface of course LED is better.

So in summary LED is the better option for a general purpose light but at the moment it can't fully replace HID and you only get what you pay for. However I hope that this enlightens you and you no longer believe the garbage quoted on the outside of the packaging, Light is also very subjective and everyones eyes are different!