Night diving and light discipline

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TSandM

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Night diving has some things in common with cave diving -- you are very depending on your dive lights, to know where you are, to see stuff, and to communicate.

In cave diving, you spend quite a bit of time on what's called light discipline. What is it? It is learning how to use a light in the dark so that it helps you AND your team, and doesn't become a problem.

First off, you use your light in smooth, fluid movements. If you are swimming along and looking at stuff, you swing your light back and forth in a fairly slow and rhythmic fashion. If you are really disciplined, you make sure your light crosses in front of your buddy's field of view every 30 seconds or so, so your buddy can use that information to conclude that you are well. Rapid, jagged, or erratic light movements will alert a trained buddy to the fact that you are having some kind of problem, and a well-trained buddy will ask you if you are okay, or even stop and turn around to see if you're all right.

Second, if you are using hand signals, you light your hands, and in such a way that the light crosses in front of your body, rather than shooting out toward your buddy. If you don't light your hands, your buddy likely can't see your signals. If your light gets too close to in front of you, your buddy will see stars but nothing else!

And that leads to the next concept, which is never to shine your light in your buddy's eyes. Human eyes are capable of an enormous amount of accommodation, to account for low light. It takes very little illumination to be able to see in the dark, which is why I personally do my tropical night dives on a backup light. But if you shine your light in someone's eyes, it will be 30 seconds or more before they can see anything to speak of at all, which means that, to all intents and purposes, they are blind. Any time you look at your buddy, keep that light aimed down -- you can move it up if you need to "paint" them to check something.

I think all of the above are generally agreed upon, but I'll add a last little bit which is my own. As mentioned above, the human eye is capable of enormous light-gathering if allowed to do so. This means that, if you are night diving in clear water, you really need very little light with you. Nocturnal animals don't LIKE light, and if you are waving a big video light around, many of those critters will have hidden before you ever get near them. A good backup type light (UK SL4 eLED or DRIS backup, for example) is plenty, in my personal opinion. The murkier the water, the more power you need, but in the tropics, small lights work just fine.
 
AKA "no disco lights" [emoji6]

...First off, you use your light in smooth, fluid movements. If you are swimming along and looking at stuff, you swing your light back and forth in a fairly slow and rhythmic fashion. If you are really disciplined, you make sure your light crosses in front of your buddy's field of view every 30 seconds or so, so your buddy can use that information to conclude that you are well. Rapid, jagged, or erratic light movements will alert a trained buddy to the fact that you are having some kind of problem, and a well-trained buddy will ask you if you are okay, or even stop and turn around to see if you're all right...


---------- Post added October 12th, 2014 at 07:06 PM ----------

Nice post btw (whole thing). Had seen another topic earlier about communicating underwater if hearing impaired, a lot of these points are relevant during day dives as well as night dives.
 
we have run into the additional rule of "no strobe for your tank marker light".

flashing strobes are "reserved" to mark exit points. either tethered some where near the shore dive exit or suspended beneath the back of the dive boat.
 
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Nocturnal animals don't LIKE light, and if you are waving a big video light around, many of those critters will have hidden before you ever get near them.

Found that out when I took up doing video. I had a couple of 1000 lumen light heads and even when you turn them down, in clear tropical water that's a lot of light. I found that the critters run back and hide so not only do you not get all that great of shots, it can screw it up for those around. For the most part I have quit doing night video. Now I just enjoy the night dive with a single 1000 lumen light from Bigblue which I can dial down to a reasonable amount of light.
 
I second that, leave your big light at home for tropical reef dives. It disturbs animal life, and in my opinion it also kills the mood of a night dive is everything is lit bright as day.
 
Interesting about the strobes. Here in low viz we often dive them in the day as well attached to the pillar valve. they can be a bit of a nuisance on a good viz dive at night though.
 
It's funny/sad. So few recreational divers understand this, to the point that I find that when you do try to signal someone with a light they ignore it because they assume that YOUR frantic light waving is the same "standard frantic light waving" that every other diver does.

One night dive I was desperately signalling my liveaboard instabuddy, trying to get his attention to see a huge octopus. I was signalling him with the TWO Sola 2000 lights attached to my GoPro mount. That's 4,000 lumens of LED power in crystal-clear Caribbean water... waved right across his light's path. So I knew he saw it. He never reacted, and never got to see his first octopus.

Back on the boat he admitted "Yeah, I saw your light... but didn't think anything of it."

Good thing I wasn't entangled and OOA...
 
I really like my Big Blue 300 lumen shorty backup for tropical night diving. It has a 40 degree beam angle w/o a hot spot. Just a nice wash of light. Not too bright...like me. :dork2:
 
I find it difficult being part of a group of divers meandering around a reef, with beams criss-crossing and jumping all over the place, as people point the beams rapidly from here to there in search of critters. It's hard to get anyone's attention or keep track of where certain members of the group are.

Most of my diving is tropical reef. I contemplated getting a more powerful light like the DRIS 1000 just because it seemed like I should have a "better" light than I do, but in the end I decided it made sense to stick with my economical Dorcy Penetrator 220s. For this type of diving, it makes sense to have the LEAST bright light that will do the job. Between my wife and I we have four of them.
 
https://www.shearwater.com/products/peregrine/

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