Hey, I'm in the market for my first dedicated flashlight and am attracted to the Foursevens Quark Mini AA2. However, I'm a bit turn off that it's the same model as existed roughly 2 years ago.
Given that my background is in computers I am used to a field where technology is continuously becoming updated and what is the best today will be outdated tomorrow.
Even though computers and LEDs are a form of electronics do they have this as a similarity? What I'm asking is if someone could explain or redirect me to something that could explain what exactly is a XP-G R5 and how that differs from a XR-E Q5. Why the XP-G R5 hasn't changed for the last 2 years and if it does does the same technology improve or is replaced by something else.
In short, someone care to help me clear my flashlight ignorance?
Thanks,
Rav.
Alright! Let's get you up to speed!
What you're saying has 2 parts. the "XP-G" portion, and then the "R5" portion.
The XP-G is what the entire LED is referred to as. it is a 1.4mmx1.4mm chip in a small 3.45x3.45mm package.
The XR-E, on the other hand, is an older LED. it consists of a 1mmx1mm (or 0.9mmx0.9mm for the newer ones) chip (aka die) in a 7mmx9mm package. see the difference?
Now, the second part of your question. "R5" refers to the LED's efficiency bin. LEDs, when created, aren't all identical due to impurities during creation. As such, they are "binned" (aka sorted) according to their efficiency and even tint (color). The R5 refers to the efficiency (note that efficiency is NOT efficacy, I'll talk about that in a moment)
Back to the R5. In case of the XP-G, that means it makes 139 lumens at 350mA (generally what LEDs are binned at)
Comparing this to your XR-E Q5: 107 lumens at 350mA
However, that isn't all! The forward voltage (Vf) of the emitters is also different!
Now we can get to efficacy! Efficacy, well, Luminous Efficacy, basically defined as lumens per watt. This figure is more important than efficiency, which is usually considered as just the LED(aka emitter) bin.
In your case of XP-G R5 vs XR-E Q5(I'll be comparing them at 350mA):
The XR-E Q5 produces 107 lumens @ 350mA, with a forward voltage of 3.3V
in comparison,
The XP-G R5 produces 139 lumens @ 350mA, with a forward voltage of 3V!
The XP-G Has a smaller package, produces more lumens at the same current, and has even higher efficacy!
How higher? 132.4 LM/W (lumens/watt) vs 92.6 LM/W!
Now, how much more power does the XR-E consume than the XP-G? 1.155W compared to 1.05 W - and it has less output!
How's that for an upgrade?
Numbers wise, that's not bad at all, but most of us are human, we have to apply something called the inverse square law - we do not see light increases as linear, we see them logarithmically.
I.E. for a flashlight to be visually 2x brighter to our eyes, it has to actually be 4x brighter. The difference isn't as noticeable!
If you're still reading this, I'd like to add some more information!
LED efficacy tends to drop the higher current you drive them out - they have diminishing returns, but let's compare the XP-G R5 to a XR-E Q5, this time, at 1Amp! (many flashlights drive them this high)
The XR-E Q5 produces 235.4 lumens @ 1000mA, with a forward voltage of 3.7V
in comparison,
The XP-G R5 produces 347.7 lumens @ 1000mA, with a forward voltage of 3.397V!
The XP-G is 102.4LM/W @1A, and the XR-E is 63.6LM/W @ 1A
Now, how much more power does the XR-E consume than the XP-G? 3.7W compared to 3.397 W - and it has less output!
Another popular emitter is the XM-L - it has a slightly larger package and a much larger die (2mmx2mm!)
That one does 388 lumens at 1 amp, 12.9.3 LM/W, has a 3V Vf, and consumes 3W! even lower than the XP-G, but it has a larger die than the XP-G, allowing for more efficacy.
Another point! The XR-E is rated to 1amp, the XP-G is rated to 1.5amps, and the XM-L is rated to 3 amp!
each of these emitters have a lower thermal resistance than the next, making them quite easy to heatsink. How's that for upgrading technology?
have a look at the XT-E and XB-D for budding technology. The XT-E is the same package size as the XP-G, but offers even more improvements in efficacy! The XB-D is even smaller than the XP-G, but still has a similar output!
Now, for a quick reference, here's the order in which tech was released.
XR-E(the original "big package!), XP-E(shrinking the XR-E!), XP-G(XP-E, but with a larger die!), XM-L(big package with a huge die!), XT-E(going back to the XP-E and improving efficacy!), XB-D(shrinking the XP-E package while retaining efficacy!) (not including lower cost emitters)
Hope this helped
Craig
PS: cool pix here
http://www.candlepowerforums.com/vb/showthread.php?270419 I've been meaning to update the thread with better organization. haven't found time to, lately!