Crees vs 20 mA Traditional, Best Focus?

[ahx66]

The story is that I have built many lights from 20 mA LEDs (in application to bike lighting), but am now venturing to the high wattage LEDs.

I have made 1 attempt with building a cluster of Crees (from Best Hong Kong). It was done with manually mounting the heat sink and reflector. The standard "10 degree" reflector turned out to be effectively a 30 to 40 degree flood light--even with my best effort to optimize the LED position.

In comparison with clusters of traditional 20 mA LEDs, the 10 mm 12 degree focus very well (truly 12 degree) and the 5 mm 20 degree (for more diffuse light) are quite compact bright sources. (Though not impressive individually, they are quite bright in large numbers) Although more bulky per watt w/ clusters, they actually seem to make more lumens per watt. Plus less heat (or simply a better job of spreading heat than a Cree w/ sink).

The point I'm getting at is that what looks superior on paper--that is the Crees over the 20 ma-ers in both efficiency, focus etc.--actually seem to be the opposite in the reality I have experienced.

Not sure what I could be missing here, but just wanted to see if anyone else has built both type of lights and felt similarly.

In another question, what high-wattage LED (or reflector) is focused well to, say, 10 degree or less without being bigger than say 1.5 inch?

 

[LukeA]

In another question, what high-wattage LED (or reflector) is focused well to, say, 10 degree or less without being bigger than say 1.5 inch?

Here

 

[LukeA]

In comparison with clusters of traditional 20 mA LEDs, the 10 mm 12 degree focus very well (truly 12 degree) and the 5 mm 20 degree (for more diffuse light) are quite compact bright sources. (Though not impressive individually, they are quite bright in large numbers) Although more bulky per watt w/ clusters, they actually seem to make more lumens per watt. Plus less heat (or simply a better job of spreading heat than a Cree w/ sink).

Blue light seems brighter than warmer tinted light, so that's a part of it, and I don't know if you're matching the lumens either.

That it seems like the 5/10mm clusters heatsink better is because they are worse. They conduct virtually zero heat away from themselves, unlike the Crees which heat up the heatsink rather than keeping the heat in and ruining the die with overtemp.

 

[asdalton]

Lumens are a measure of total light output, not focused light.

Regardless, properly collimated Cree LEDs will throw a beam much better than any 5mm cluster. You need to use individual optics or reflectors for each emitter, however. You can't mount a cluster of LEDs and then try to focus the whole thing.

 

[ahx66]

Lumens are a measure of total light output, not focused light.

I know what a lumen is.

To rephrase, my point was 20 mA LED clusters appear to generate more total light output per watt than Cree. Although Crees are much better on paper, that's the way it appeared in practice.

I've used my LED lights for a long time and they haven't seemed to dim over time, but then again on a bike they have a lot of airflow. But considering the heat issue, I want to build another Cree cluster w/ ones that are properly focused.

Does anyone know if you can buy Cree LEDs that have built-in focusing in the plastic (that is narrow, like 10 deg)?

 

[LukeA]

Does anyone know if you can buy Cree LEDs that have built-in focusing in the plastic (that is narrow, like 10 deg)?

Nope. You can't.

 

[ahx66]

Forgot to make it clear, but the cluster of Crees I built did in fact have a reflector (20 mm 10 deg) for each individual LED and not one big reflector for them all.

Still, the 10 deg spot was weak and the 60 degree or so washout area was where most of the light seemed to go. This which leads me to believe that simple reflectors will only focus well if gigantic, which then defeats the purpose of making a compact light.

Perhaps total internal reflectors are closer to the answer? For compactness, beam tightness and uniformity how well do they work?

 

[asdalton]

Forgot to make it clear, but the cluster of Crees I built did in fact have a reflector (20 mm 10 deg) for each individual LED and not one big reflector for them all.

Still, the 10 deg spot was weak and the 60 degree or so washout area was where most of the light seemed to go. This which leads me to believe that simple reflectors will only focus well if gigantic, which then defeats the purpose of making a compact light.

Perhaps total internal reflectors are closer to the answer? For compactness, beam tightness and uniformity how well do they work?

A 20-mm reflector should be adequate for decent throw *if* it was designed to be used with a Cree emitter (example here). The same is true for a Cree-compatible TIR optic like Gene Malkoff uses in his drop-ins.

Because of their "can" package, Cree LEDs emit much less light sideways than other brands. Reflectors used with a Cree need to be tall and deep in order to collect the light effectively, not just wide. For example, the stock C/D size Mag reflector works very well with a Luxeon or Seoul emitter, but poorly with a Cree.

If your goal is to direct as much light forward as possible without concern for loss of sidespill, then an appropriate TIR optic will be superior to a reflector.

 

[ahx66]

Makes sense, since a reflector acts more on the light thrown to the sides. Perhaps a nice tight focus can be achieved afterall

I guess with the experience of Crees and shallow reflectors I developed a dislike for the reflectors.

But now I think I'm going to be buying some of the Seoul P4's (or Luxeon III's). Do those also throw out most light in front? It probably doesn't matter, as I'm going with the optics (also called TIR's, right?)

 

[asdalton]

The SSC P4 is much more adaptable to traditional reflectors than the Cree is. So are the Luxeons. But if you go the Luxeon route, I recommend getting the new K2-TFFC, which is much more efficient than the older Luxeons (including the original K2) and also has a pretty consistently warm tint. The K2-TFFC is already used in the new Inova T-series lights, but the bare parts may be difficult to find right now.

I don't know the brands of optics that are able to work with the Cree, but PhotonFanatic is selling reflectors and optics to go with the SSC P4 in this thread. He also sells the SSC emitters and stars.

 

[Nitroz]

You should try using an IMS 20 relfector with the Cree LED.

 

[Nitroz]

How much power did you put into the Cree LEDs? It would be better if you purchased your Cree LEDs from a dealer that you can trust will sell you exactly the best LEDs your money can buy.

3 Cree LEDs x 350mA=300 lumens. This would put out much more light then quite a few smaller LEDs.

 

[TorchBoy]

Re: Crees vs 20 mA traditional; best focus?

I guess with the experience of Crees and shallow reflectors I developed a dislike for the reflectors.

But now I think I'm going to be buying some of the Seoul P4's (or Luxeon III's). Do those also throw out most light in front? It probably doesn't matter, as I'm going with the optics (also called TIR's, right?)

The output from Seoul and Luxeon LEDs is a bit wider than the Cree LEDs.

If you're going with TIR optics it wouldn't matter if you used Crees - they work well with them. I think this is the KD optic LukeA was trying to link to. They also have a ten pack.

 

[LukeA]

Re: Crees vs 20 mA traditional; best focus?

If you're going with TIR optics it wouldn't matter if you used Crees - they work well with them. I think this is the KD optic LukeA was trying to link to. They also have a ten pack.

The ten pack is a better deal per piece. (the product page is broken, but you can add it to cart from the search result I linked to here. It's the first result).