Led die for the best throw (XP-E2/XM-L2/XP-G2) ?

easilyled

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Okay, you're right. 4sevens is a crappy company that intentionally designs the XPG versions of their lights to under-perform. They're obviously being paid off by the XML designers.

Now that I've had a closer look at my XPG Quark, I see they've painted the lens black! No wonder why it doesn't throw as far as the XML Quark!

Is it really that difficult for you to understand that your Quark XM-L2 is probably driven at twice the current of your XP-G2 which accounts for why the throw is similar when the XP-G2 die is only half the surface area?

Instead of indulging in a realm of mysticism, why not embrace a little scientific theory? Its not really your enemy.
 

WalkIntoTheLight

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Is it really that difficult for you to understand that your Quark XM-L2 is probably driven at twice the current of your XP-G2 which accounts for why the throw is similar when the XP-G2 die is only half the surface area?

Instead of indulging in a realm of mysticism, why not embrace a little scientific theory? Its not really your enemy.

That's a pretty good trick, considering they both have the same run-time.

So I am actually curious. Why do you repeatedly ignore the spec sheets that Cree publishes? The XML is clearly much brighter at the same current, and it also uses a lower voltage so uses less power.

I understand that all else being equal, the smaller XPG can be used to throw further than an XML. But, as I've pointed out many times, all else is NOT equal. Besides what I've already mentioned, just because you can design a theoretical reflector to take advantage of a smaller LED, doesn't mean that in practice the reflector and design will be perfect. Any imperfections will reduce the throw of an XPG more than it will a larger form like the XML.

Again, I'm not saying every light that uses an XML will out-throw an XPG. Clearly, some designs will make better use of the XPG, especially if they're designed to be good throwers. But, as I've given you a real-world example, the brighter XML is sometimes able to out-throw an XPG, just because of its brightness. And many of the best throwers do use XMLs, not only because they're more efficient, but because they can drive them far harder and pump out even more brightness.

I really do understand your argument, and agree with it in some cases. I don't understand why you're blind to the other points.
 

easilyled

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That's a pretty good trick, considering they both have the same run-time.

So I am actually curious. Why do you repeatedly ignore the spec sheets that Cree publishes? The XML is clearly much brighter at the same current, and it also uses a lower voltage so uses less power.

I understand that all else being equal, the smaller XPG can be used to throw further than an XML. But, as I've pointed out many times, all else is NOT equal. Besides what I've already mentioned, just because you can design a theoretical reflector to take advantage of a smaller LED, doesn't mean that in practice the reflector and design will be perfect. Any imperfections will reduce the throw of an XPG more than it will a larger form like the XML.

Again, I'm not saying every light that uses an XML will out-throw an XPG. Clearly, some designs will make better use of the XPG, especially if they're designed to be good throwers. But, as I've given you a real-world example, the brighter XML is sometimes able to out-throw an XPG, just because of its brightness. And many of the best throwers do use XMLs, not only because they're more efficient, but because they can drive them far harder and pump out even more brightness.

I really do understand your argument, and agree with it in some cases. I don't understand why you're blind to the other points.

You're quite correct to say that I'm blind to the fact that an XM-L2 can out-throw an XP-G2 at the same current. So are the laws of optics. It just won't happen in the real world.

For your information at the currents that the Quark 2AAs are driven at, the XM-L2 is not overwhelmingly brighter than the XP-G2. Only a little brighter. Furthermore the XM-L2 isn't overwhelmingly more efficient than the XP-G2 at these currents. Just a little. Maybe about 20%.

This cannot make up for the fact that the XP-G2 is less than twice as small.

The equation of surface brightness which is proportional to throw is overall output divided by die area.

Therefore the XM-L2 would have to have over twice the overall output to throw the same as the XP-G2.

It certainly doesn't have twice the brightness at the same current.

Instead of just assuming that the drive currents in your Quarks are both the same (without any evidence) and that there isn't a mistake in the manufacturer's specs for beam distance, why don't you measure these and provide some facts and figures.

Then you can astound all the physicists and disprove everything that has been written in any of the physics books.
 
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RedForest UK

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easilyled is right in that an XP-G2 driven at the same current as an XM-L2 will throw further (given appropriate optics for each), unless that current is way over what the XP-G2 can handle, such as 3 amps on a normal MCPCB or 5-6A on a direct copper bonded one. That's just the way the physics works. The XM-L2 will be more efficient, and yes this is even more so than CREE spec sheets suggest as it has a lower vf and so consumes less watts at the same current, which is a particular advantage for boost circuit based lights (e.g. AA or 2x AA) due to circuit efficiency. However, that additional light will be emitted from an area much wider than it can make up for surface brightness wise and so need a comparatively wider reflector to collimate it enough to match the throw of the smaller die LED.

With regards the Quarks, both use a relatively aggressive OP reflector, which somewhat negates the throw advantage of the smaller die XP-G2 and probably gives a greater importance of raw power for absolute throw, favouring the XM-L version. Also, whilst both have the same stated runtimes, this is based upon ANSI standards which rate a single run down to 10% output. I believe the XM-L versions have a timed stepdown, which means immediately after turn on they are consuming a higher current, which artificially biases throw towards that version. This higher current drops down to the same (or a little less than the XP-G version due to the vf differences) for the majority of the run though, allowing no appreciable difference in runtime if it is never turned off and on again in that time to reactivate the higher mode.
 
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