Lumen comparison

[rescue15]

I am almost finished a DIY canister light. The head and canister is about 90% complete and I am trying to settle on the internal components. I will post my project and parts list when it is finished.

I have been reading threads on SODS, south west mafia and CPF. Some threads say 200 lumen is a very bright light and others talk about 1000 lumen.

My question is what are people using for primary lights? How many lumen is put out by a 21 Watt HID, a 50 Watt Halogen and a 35 Watt halogen?

What do I need to use to attain these outputs with LED's? Can 500 to 700 lumen be attained with a single LED (from DX) and a buck puck? What would you recommend?

Thanks,
Steve

 

[350xfire]

SSC P7 will put out plenty of light for a dive. Rated at 700-900. Don't know how accurate that is. I have dove with one SSC P7 with a buddy running a Salvo 21W LED and it was good enough to keep up. I now have a 3-SSCP7 for video that will beat the pants off the Salvo. I think Salvo claims 1100 lumens.

 

[HEFFAY]

Are you looking for a flood type light? Or more of a tight focused beam for signaling?

 

[rescue15]

I would like a fairly tight beam with some spill. It wluld be nice to do it with 1 LED, I could work with up to 3. I was looking at the DX reflectors. Does anyone know the lumen of this... http://www.dealextreme.com/details.dx/sku.9358


or the quality of this.... http://www.dealextreme.com/details.dx/sku.14413

I have been looking at this but am worried about the quality... http://www.batteryjunction.com/tle-300.html

Steve

 

[Packhorse]

Lumen out put starts to become quite meaning less due to all the variables.
I have a 200-225 lumen hand held light that can shine as far as a 21 watt HID salvo (1500 odd lumen).

You need to take into account how many lumen are lost because they dont "exit" the light. The optics may only be 80% efficient. The front lens may only be 95%.
The LED may only produce 200 lumen when cold and getting full current. The LED may be rated at upto 200 lumen.

A 200 lumen torch with a 4 degree beam will be 16 times brighter than a 200 lumen torch with a 16 degree beam. In fact for the 16 degree beam to be as bright you would need 3200 lumen behind it.

I have built a P7 base light (upto 900 lumen) and it didnt come close to a 21watt salvo.
I built a 4 x Q5 light and it blows away the salvo.

My advice is forget lumen. decide what it is you want to achieve and build it. Dont get tied up in irrelevant numbers.

 

[Packhorse]

or the quality of this.... DealExtreme: $29.63 SSC P7-C 2800mA LED Module with Copper Base (3.6V~8.4V)

That is the reflector I used for my P7 mag dive light. P7 LED from DX too so that was probably the same or similar. Drove it with 2.8 amps so that would be the same.

It was OK. Much better colour than a 35w halogen over driven to 50 watt) but not quite as bright. I still preferred the LED.
A single LED makes it a little easier to build but best results will be gained from multiple LEDs
YMMV.

 

[DIWdiver]

I don't agree COMPLETELY with Packhorse that lumens are meaningless. He's absolutely right that you can't just compare lumens. Lumens is a measure of total light output. Brightness depends on how it's concentrated. So Packhorse is absolutely right that beam width has a HUGE impact on lumens vs brightness. For beams narrower than flood, a reasonable approximation is that for a given number of lumens, the brightness fall as the square of the beam width. He's right that optical efficiency is very important and can vary a lot. The front lens can be up to 99% transparent (UCL lenses available for above-water use, non-reflective coatings, thin glass) to as low as 90% or much less (1/4" Polycarbonate starts out around 90% and falls as it gets worn). Don't even get me started on lenses and reflectors.

That said, you can compare different lights based on lumens, IF EVERYTHING ELSE IS SIMILAR. A single 500 lm LED will beat 3x100 lm LEDs if you have good 6 degree optics on both and similar lens in front of them. But I'm sure Packhorse would say (and rightly so) that it's hard to guarantee similar efficiencies in the optics. However your chances are better with the 500 lm LED than they are with the 3x100 lm LEDs, unless you have reason to believe there's a substantial disparity in the optics, AND you know which direction it's in! Similarly, a 1000 lm LED array is likely to beat a 10W HID that claims 470 lm (one well-known manufacturer) if the beam width is similar, but th 18W HID is likely to give the LED a run for its money.

IMHO, you want to decide on the beam pattern you like (most folks say 6 degrees or narrower for daytime, wider for night), make your best guess about the optics efficiency, then compare based on lumen rating. As you are building yourself, and have control over many of the variables, I think lumen rating is even more relevant for you than for someone just buying a light.

D