Lumens for primary?

[stuartv]

I'm trying to figure out how many lumens it makes sense to have in a primary light.

I have a couple of handheld lights now (Dive Gear Express DGX 600 and DGX Max). They have the Cree XM-L2 U2 LED emitters which are rated up to 1000+ lumens. DGX actually claims 600 lumens out the front. The are BRIGHT.

I've started tech training and my instructor has recommended to get a proper canister light as my primary. Looking around, it seems like a lot of them are in the 1500 - 2000 lumens (2300 - 3000 claimed) range.

When I have used my 600 lumen lights, they have seemed to me to be plenty bright. Sometimes, too bright. It has been pretty normal that they are bright enough that glare from backscatter starts to make it hard to see past 10 feet or so. This makes me wonder how useful a 2000 (actual) lumen light would be. I wonder if that wouldn't be too bright for any conditions that were less than 75+ feet of visibility. I.e. 90+% of the time, it would actually be too bright?

Can any of you shed some light (ha ha!) on this for me? Is there really a reason to have a 2000 lumen light? I can see maybe wanting a can light for the way-longer-than-I'll-need burn time. But, I'm not clear on when I'd ever actually benefit from having 2000 lumens coming out the front - especially in an 8 degree spot.

Thanks for any insight.

 

[RJP]

In tech, the light is used as much as a signalling device as it is for seeing. Accordingly, the further you can throw a beam, the further you can signal. It's counterintuitive perhaps, but in daylight in clear water you need more light than you would at night or in otherwise dark water.

Also, what is the beam width of the lights you are using currently? In order to signal properly you want a tight beam.

Lastly, LED is catching up quickly, but my 21w Salvo (now Light Monkey) HID still seems to cut through murky water better than any LED light I've seen.

 

[stuartv]

In tech, the light is used as much as a signalling device as it is for seeing. Accordingly, the further you can throw a beam, the further you can signal. It's counterintuitive perhaps, but in daylight in clear water you need more light than you would at night or in otherwise dark water.

That is perfectly intuitive. Except that I have not yet been trained on or experienced a need for signaling with a light in daylight. When do you do that? Is that something you might do in highly turbid water, during the day?

Also, what is the beam width of the lights you are using currently? In order to signal properly you want a tight beam.

DGX 600 and DGX Max are both approximately 8 degrees.

Lastly, LED is catching up quickly, but my 21w Salvo (now Light Monkey) HID still seems to cut through murky water better than any LED light I've seen.

They claim 1500 lumens for that light. There are LED lights claiming 2300 lumens actual output, and costing less than $300. I've seen the discussions about "cutting through" better. I'd really like to see some science behind that. Number of lumens out the front, beam angle, and beam temperature are the only numbers I know of to apply to that and I don't see how less lumens can cut better unless it's something about the beam temperature (which certainly could be).


Regardless, the question stands: Have you found that a 600 lumen light was not bright enough and a 1500 lumen light let you accomplish something that you couldn't with a 600? Or do people with 1500 lumen lights mostly run them on a Low setting (getting more like 600 lumens) the vast majority of the time?

Does 1500+ lumens not end up making it harder to see a lot of the time (because of turbidity? Kind of like not wanting to use High beams on your car in fog?)?

Will I be sorry if I buy a can light than only puts 600 lumens out the front? Normally, I would be all about buying "bigger" and then using it on a Low setting, if that's all I needed. But, in this case, it's a lot of extra money and bulk on the back of my hand if it's going to turn out I pretty much never need the extra brightness.

 

[eelnoraa]

I have a couple of handheld lights now (Dive Gear Express DGX 600 and DGX Max). They have the Cree XM-L2 U2 LED emitters which are rated up to 1000+ lumens. DGX actually claims 600 lumens out the front. The are BRIGHT.

XM-L2 U2 bin LED is rated at 1000 lumen under the ideal condition, ie 3A into the LED, but with head issue, run time issue, LED life longacity issue ... which is un-archieveable in reality. DGX600 with 1 18650 battery output about 350lumen. XM-L2 LED with a canister can go up to about 600lumen per LED. That is about it for XML LED. There are other LEDs that can do better, but not Cree XML.

The question here really is about the real lumen value vs inflated lumen value. A true 1200lumen light is very bright, that is about a 21W HID will do. Those 3 cree canister light on ebay that claim to have 3000 lumen actually output about 1500-1800 range, which is very good. But if you want to see what is true 2000+ lumen looks like, you need to get a UWLD light.

As to "do you need a 2000 lumen light?", the question only you can answer. If I can afford one, I will sure have one. At this moment, I have light monkey 21W HID. I like it and I don't want to spend money to upgrade a perfectly working light.

 

[tbone1004]

this is a very difficult topic to address.

On one hand a tight beam, high intensity light will in fact cut thru the water much better for signalling, useful in murky caves. On the other hand, in open water, there is no wall to signal off of, and if you have a black mask skirt, you can't signal into the mask of your buddy if you're behind them so it is crucial to stay within one kick cycles distance of each other for touch contact.

I see no reason to move to a canister light in your situation, you have lights that are brighter than the old standard 10w HID's, and if you are staying within their burn times on the dives you are doing, the canister will only add complexity to your rig.

Now, some lights like the UWLD-15, are a true 1500lumen out the front, it is a very bright light, but the spread is fairly wide, not the best for murky water, but perfectly satisfactory in the cave. If you have enough light for what you need, and the burn time is sufficient, there is no need to move to a bigger/brighter light.

 

[RJP]

That is perfectly intuitive. Except that I have not yet been trained on or experienced a need for signaling with a light in daylight. When do you do that? Is that something you might do in highly turbid water, during the day?

Any time I want to get someone's attention. With a bright/tight enough light I can shine a beam where someone is looking and get their attention. The clearer and brighter the dive... the stronger/brighter light you need in order to be able to see it.

PS - do also note that you don't want to have a light that will blow-away your buddy's light. If you were blasting a 50w HID in a wreck... you'll never see your buddy's 10w light.

 

[decompression]

Soon Stuart at the depths you'll be diving you see the need for a very bright primary light. The DGX is a good back up (in some situations). A good question about how bright though. Certainly it'll depend on many variables. Simple way, see what the locals are diving.


Sent from my iPhone using Tapatalk

 

[stuartv]

I see no reason to move to a canister light in your situation, you have lights that are brighter than the old standard 10w HID's, and if you are staying within their burn times on the dives you are doing, the canister will only add complexity to your rig.

Now, some lights like the UWLD-15, are a true 1500lumen out the front, it is a very bright light, but the spread is fairly wide, not the best for murky water, but perfectly satisfactory in the cave. If you have enough light for what you need, and the burn time is sufficient, there is no need to move to a bigger/brighter light.

I am about to start diving doubles and doing deco training. So, I am facing the possibility that my current lights will not have enough burn time. I don't know if they will or not (yet). I think they will, given the max capacity Panasonic batteries I got for them.

I'm just trying to educate myself now, so that if I end up needing more burn time I already have an idea of what I want to buy. I don't mind having an extra $50 handheld light laying around. I don't want to spend $1000 on a light at all, but I also don't want to spend $200 or 300 and then end up getting something brighter later and having a $200 - 300 light just laying around.

 

[tbone1004]

so the best suggestion I'd have is to do this.

Run a true burn test on the lights. Put them in a 5g bucket with water, turn them on high, let them go. Fully charge, repeat on low. That will get you an actual burn time. Take 2/3's of this number and that is your burn time. Take the depth you're planning on going, with the lowest sac rate you've seen, and the doubles you are planning on diving. I.e. for me the answer is 130ft, LP104's, and SAC of 0.4. 280cf of gas, 2cfm DAC, gives me 140 minutes of burn time required for my primary. Will round that to about 180 minutes ish. DGX quotes burn time at an hour, so you'd need 5 lights for that dive *3 for the dive, and 2 backup*. Again this is worst case scenario, so I'd probably only carry 4 as you aren't going to be at depth for long as SAC rate is likely going to be higher, you obviously aren't going to have your full dive time at depth, and you don't have your lights on at deco in OW. You also probably aren't going to spend close to 2 hours at 130fsw.... LONG deco.

Now, at 600lm output, you are better than the 10W HID's which are about the only ones you can get cheap. For reference, the baby UWLD, the LD15 is pretty comparable to the LM21W HID which is the minimum HID I'd recommend getting, and the LD is a few hundred bucks cheaper with a much smaller canister. Depth isn't really going to change your light requirements and if the guys are surviving with 10W HID's, then you'll be fine.

So you have a bit extra task loading having to switch lights after 40 ish minutes, but at the same time you can get a pair of them for $100. If you want to spend over a grand, the LD35 is really the only light I'd go with at this point. More light, better burn time than Light Monkey, and they're the only other game in town for the big lights until the Deep Six light is officially released in a few weeks which is nice, but will be nicer because it is cheap. Picture below from their FB page.

Official recommendation is to get 4 DGX Max or a pair of the Cave Adventurers Explorer lights *just got mine in today and they're spectacular*, and wait for the canister until you really have a better idea of what you're looking for in a light.
Cave Adventurers - Explorer back-up lights - Marianna, Florida USA - Never Undersold!

 

[stuartv]

Official recommendation is to get 4 DGX Max or a pair of the Cave Adventurers Explorer lights *just got mine in today and they're spectacular*, and wait for the canister until you really have a better idea of what you're looking for in a light.
Cave Adventurers - Explorer back-up lights - Marianna, Florida USA - Never Undersold!

Thanks, Tom!

So, for me, double 120s, 130', 0.55 SAC, I get a max dive of about 90 minutes.
Roughly the same numbers as you.

The CA lights look like a single emitter with the same single 18650 battery as the DGX 600. What makes it worth 2.5X the price? I did not see output or burn specs on the page you linked.

And if I were going to spend another $100-120 on 2 DGX or 1 CA light, what about spending $200 for the Orca Torch 950 can light, which is supposed to have 2:45 burn time (on High)? That includes a Goodman handle and I wouldn't have to swap lights during a dive. Or the Ano CL2300?

$100 for 2 more DGX 600s may be my best option. I think they would make good truck/house lights when I eventually replace them with a can. But, I am still curious about the Orca 950, or that Ano light that is claimed to be 2300 lumens and is $260(? I think)

---------- Post added August 24th, 2015 at 08:33 PM ----------

Oh, and for the math, lowest SAC I've seen over a whole dive? Or a dive segment? I've had around 0.47 on just the drift portion of a dive, when you leave out the heavy burn at beginning and end.