Handheld Primary Light (Cave)

[Underwater Tourist]

That could easily just mean that their eyes adjust as it gradually dims and they just don't really notice that they actually cannot see as much of the cave or see it as well as they could at the start. But, it probably mostly means that, the way they use them, the light does not actually dim that much during a 3 or 4 hour dive.

I tried to spot the dimming, and yeah you can't easily catch it because it happens gradually. But if you keep a mental image of a part of a cave at the beginning of the dive and then compare it to what you see at the end of the dive, then its noticeable.

Here is how much their 150000 lights dims; pretty much all of BBs drop a lot after 60 minutes. So they dim alot.

Just wanted to mention this point in the thread in case some new members haven't seen it before. The key implication is that when you are paying extra for supposedly higher lumen BB lights, your lumens will be gone pretty quickly, which brings the question what did you pay for?

you can click around for more lights, but the picture will be pretty much the same: We Test Lights | Bigblue Tests and Teviews

 

[tbone1004]

I certainly am aware of the many times tbone has posted about that. But, I have also asked my various cave diver friends that use them if they have had any issues with that. They all say no. That could easily just mean that their eyes adjust as it gradually dims and they just don't really notice that they actually cannot see as much of the cave or see it as well as they could at the start. But, it probably mostly means that, the way they use them, the light does not actually dim that much during a 3 or 4 hour dive.

I also expect that I won't be running it on High very much. I generally run my LD-40 on Medium, at best. A BB 9000 that has a 2900 lumen spot, and I'm running that on Medium, will probably hold its brightness for far longer than an hour.

Anyway, it's just something I will try out. If I don't like it, you'll probably see it in the SB Classifieds in a couple of months for sale at a huge discount off retail...

the drop happens near instantly and your eyes can adapt. Professional photographers didn't believe it until they did a timelapse with a dslr in manual mode. You don't notice it unless you are in the cave against a light that actually has that kind of output, i.e. a LD-40 on high. My issue with them is that they are an unscrupulous company, has little to do with the lights themselves since they discontinued the bombs that they were making for a while. Either way, no proprietary batteries in handhelds for me, those batteries and chargers are terrifying. Either way, the shop you work for is a dealer so it's strategic for you to use those brands and I can't fault anyone for choosing gear that strategically aligns with their business. I can disagree with the choice, but it's not your choice to make on which brands your shop is a dealer for but you would be a fool for not taking advantage of the dealer pricing which effectively makes the BB lights disposable

 

[stuartv]

I tried to spot the dimming, and yeah you can't easily catch it because it happens gradually. But if you keep a mental image of a part of a cave at the beginning of the dive and then compare it to what you see at the end of the dive, then its noticeable.

Here is how much their 150000 lights dims; pretty much all of BBs drop a lot after 60 minutes. So they dim alot.

View attachment 803751


Just wanted to mention this point in the thread in case some new members haven't seen it before. The key implication is that when you are paying extra for supposedly higher lumen BB lights, your lumens will be gone pretty quickly, which brings the question what did you pay for?

you can click around for more lights, but the picture will be pretty much the same: We Test Lights | Bigblue Tests and Teviews

As I said, I doubt I'll be running it on High much. So, in the example shown, it would be much more useful (to ME) to see a graph showing what the output is when set on Medium vs Time.

Would it start at somewhere near 7500 lumens and then hold that for 60 minutes before starting to dim?

 

[stuartv]

the drop happens near instantly and your eyes can adapt. Professional photographers didn't believe it until they did a timelapse with a dslr in manual mode. You don't notice it unless you are in the cave against a light that actually has that kind of output, i.e. a LD-40 on high. My issue with them is that they are an unscrupulous company, has little to do with the lights themselves since they discontinued the bombs that they were making for a while. Either way, no proprietary batteries in handhelds for me, those batteries and chargers are terrifying. Either way, the shop you work for is a dealer so it's strategic for you to use those brands and I can't fault anyone for choosing gear that strategically aligns with their business. I can disagree with the choice, but it's not your choice to make on which brands your shop is a dealer for but you would be a fool for not taking advantage of the dealer pricing which effectively makes the BB lights disposable

Unscrupulous because they say, for example, 15000 lumens, but then it dims over time, so it's not 15000 lumens for most of its burn time?

Meaning, unscrupulous because their lights work that way? Or unscrupulous because they don't detail out in their documentation that they work that way?

Or unscrupulous for some other reason?

 

[Underwater Tourist]

As I said, I doubt I'll be running it on High much. So, in the example shown, it would be much more useful (to ME) to see a graph showing what the output is when set on Medium vs Time.

Would it start at somewhere near 7500 lumens and then hold that for 60 minutes before starting to dim?

I don't have such a graph

But if I were to speculate with my 0 knowledge of battery and light technology then I would say:

-since on high 15000 light starts at 13,500 (i.e. 90% of the advertised output)
-then 9000 light should start at 8100 (90% of 9000). 8100 is the max output it actually gives in real life
-so on medium lets say a 15000 (aka 13,500 BB light) produces 4000 lumens
-then we can use a chart for an existing 4000 lumen light as a proxy to what you might get

again, all of this is just speculations that I pulled out from where the light doesnt shine

 

[tbone1004]

Unscrupulous because they say, for example, 15000 lumens, but then it dims over time, so it's not 15000 lumens for most of its burn time?

Meaning, unscrupulous because their lights work that way? Or unscrupulous because they don't detail out in their documentation that they work that way?

Or unscrupulous for some other reason?

unscrupulous because they intentionally mislead their customers by claiming 15,000 lumens which is theoretical but none of their lights actually hit their theoretical output because their batteries can't output that much power. So you hear people try figure out why to buy a light that says 4,000 lumens for 3 hours for $2k when they can buy a 9,000 lumen for 3hr light for $500. It's very deliberate marketing tactics that don't have any disclaimers that it is a theoretical maximum light output and not an actual light output.

A more appropriate comparison since the LX20+ came out is they go "light with 1500 lumen output for 2.25hrs on high for $550" vs. the Big Blue TL3800P which is also $550 but has 3800 lumen output for 3hrs, Dive Rite must be a ripoff and they are sold that way. Completely ignoring the fact that since they both use 4x 18650's that it's not possible for the Big Blue to output 2.5x as much light for 1.3x the time, but by God that is what they are trying to sell. I take serious issue with that kind of marketing which is just intentionally misleading their customers.


Also unscrupulous because they violated federal law with their canister lights by claiming UN38.3 compliance when they didn't which almost killed a friend of mine and that lawsuit is why they no longer produce canister lights.

 

[tbone1004]

As I said, I doubt I'll be running it on High much. So, in the example shown, it would be much more useful (to ME) to see a graph showing what the output is when set on Medium vs Time.

Would it start at somewhere near 7500 lumens and then hold that for 60 minutes before starting to dim?

The issue is you have no bloody idea because they are lying to you in their marketing.

So let's do some math.
They have 4x 18650's, so 3.6v*3.5ah*4cells=50wh max for the pack, of which the BMS should only allow you to use about 45wh.
They claim 6hrs on Level 2 which is the only thing any users can actually measure so they can't lie about that. 45wh/6hrs=7.5w average draw for that burn time. The theoretical max lumen/watt of the Cree XML emitters is 100lumen/watt, so assuming absolutely no other efficiency losses your 6hr average light output is 750 lumen. How fast does that fall? I have no idea, but that is your average output, so compare that against a light that has a constant output emitter and revisit those claims.

Now, draw backwards. They claim on medium it's 4000 lumens. If it was a true 4000 lumen, that would be a 40w draw assuming no efficiency losses, light would burn for 1hr on medium, they claim 3hrs on high. See why I have issue with this company?

Dive Rite claims 50% power on the LX20+ which should be 750w for 4.5hrs using the same 4x 18650's. 45wh/4.5hrs=10w average draw. 10w*100lumen/watt=1000 lumen, factor in some misc. system losses and you get a conservative number of 750 lumens. I'll take the LX20+ please.

Now, what I would love to see is your reasoning on why someone should choose that Big Blue vs. the options that are Made in the USA and do not lie about their performance specifications. Valid reasons, the shop that I work for is a dealer, it is part of the uniform, and I get to buy at dealer cost. Invalid reasons, my friends use it and say there is nothing wrong with them *that is not a valid reason to choose a product, valid reason to have it on the list, but not a valid reason to pick it*.

 

[Capt Jim Wyatt]

I use a Dive-Rite LX20+ as my primary cave light. I cave dive a lot, sometimes 4 times a week. Sometimes dives last 3 hours. I run it on power setting 2 because power setting 1 is just too bright for me.

 

[stuartv]

The issue is you have no bloody idea because they are lying to you in their marketing.

So let's do some math.
They have 4x 18650's, so 3.6v*3.5ah*4cells=50wh max for the pack, of which the BMS should only allow you to use about 45wh.
They claim 6hrs on Level 2 which is the only thing any users can actually measure so they can't lie about that. 45wh/6hrs=7.5w average draw for that burn time. The theoretical max lumen/watt of the Cree XML emitters is 100lumen/watt, so assuming absolutely no other efficiency losses your 6hr average light output is 750 lumen. How fast does that fall? I have no idea, but that is your average output, so compare that against a light that has a constant output emitter and revisit those claims.

Now, draw backwards. They claim on medium it's 4000 lumens. If it was a true 4000 lumen, that would be a 40w draw assuming no efficiency losses, light would burn for 1hr on medium, they claim 3hrs on high. See why I have issue with this company?

Dive Rite claims 50% power on the LX20+ which should be 750w for 4.5hrs using the same 4x 18650's. 45wh/4.5hrs=10w average draw. 10w*100lumen/watt=1000 lumen, factor in some misc. system losses and you get a conservative number of 750 lumens. I'll take the LX20+ please.

Now, what I would love to see is your reasoning on why someone should choose that Big Blue vs. the options that are Made in the USA and do not lie about their performance specifications. Valid reasons, the shop that I work for is a dealer, it is part of the uniform, and I get to buy at dealer cost. Invalid reasons, my friends use it and say there is nothing wrong with them *that is not a valid reason to choose a product, valid reason to have it on the list, but not a valid reason to pick it*.

That is great analysis (as I generally expect from you, of course). Thank you!

You hit the nail on the head on the bottom line: My shop is a dealer. I am getting it at dealer cost. It's not part of the uniform, per se, but all the shop staff except me do use them. And, enough people that I know use them for cave diving that I want to try it out.

If there was a MIA light that was good as a spot beam for caves and also switchable to a good flood for video, all in one light, and I could get it at dealer cost, I would definitely want to try it! As it is now, the only MIA video lights I know of are UWLD and the 10K lm is way out of my price range and the 5K is also out of my price range and it's not cordless (which I do want).

 

[stuartv]

I use a Dive-Rite LX20+ as my primary cave light. I cave dive a lot, sometimes 4 times a week. Sometimes dives last 3 hours. I run it on power setting 2 because power setting 1 is just too bright for me.

Just curious. Why the LX20+ instead of the Dive Rite HP50?

The specs says the HP50 can go up to 3500 lumens. The LX20+ is max of 1500.

I know you said the LX20+ is too bright on High. But, reading between the lines, it looks like the HP50 LED emitter is higher efficiency.

The LX20+ runs at 1500 lumens for 2.25 hours.

The HP50 runs at 1750 (?? - whatever Medium is) lumens for 3 hours.

The LX20+ runs at Medium (750 lumens) for 3 hours.

They both use the same battery pack in the handheld version. They are the same diameter. The HP50 is about 1/2 an inch longer.

And the HP50 has the option to use the head on a canister, when you need more burn time.

I'm not trying to make it sound like the LX20+ is a bad choice. I'm trying to make it clear I don't have personal experience with either. I think the LX20+ is newer.

Is the LX20+ preferable to the HP50 because of something that I don't see just from comparing specs?

Is it just because the HP50 is $150 more expensive and you don't need the brighter beam or (possibly) longer burn time, so no reason to spend the extra money?