Looking for someone to explain some LED terms to me.
As I study and learn I fairly often see lights described as "Cree Q5" or "P4 LED".
I'm not understanding which LED's these comments are referring to. I thought the "letter number" defined the brightness of the LED. I am at a loss as to which LED is used.
I see flashlights at several of the mail-order houses that don't mention which LED is being used. How would you try to figure out which LED is used?
For each range of emitters, Cree "bins" them by various criteria
output
tint
and probably others for special needs.
Mostly here we care about output and tint. And most of the lights we talk about contain a Cree LED. So we'll stick to the Cree LEDs.
When you see P4 or Q5 you assume it has to be one of XP-C (avoid), XP-E or XR-E family. Each of these three families will produce the same output at 350mA if they are, say, P4 bin LEDs. However an XP-C can only be driven to 500mA, an XP-E to 1A and an XR-E to around 1.4A so an XR-E P4 driven to its maximum is going to put out a lot more light than an XP-C driven to its maximum.
Both P4 and Q5 bins are more or less antiques these days - I don't think Cree is actually making XR-E LEDs any more though there are huge numbers of them still in the market. There was a big change in Cree XR/XP LEDs around the time of the Q5 - they replaced the EZ1000 die that the LED was made from with the EZ900 die which is better.
It's true that most of the talk is about Cree leds, but when you see the P4 marking it might be a P4 emitter from Seoul Semiconductor, a popular choice a couple of years ago. They also made (make?) a P7 which was a quad die, much like the MC-E from CREE.
Regarding CREE:s way of preseting their bin you should now that a higher letter always trumps a higher number.
Example: Q5 don't produce as much light as a R2 when driven at the same amps.
As Don said it’s a somewhat complicated issue. However, people (and dealers) frequently misuse the terminology.
People really shouldn’t be talking about how bright or good or whatever a Q5 is since just saying Q5 doesn’t tell you what emitter they are talking about.
We generally can figure it out in the context of what is being said since some emitters never came out in Q5 bin.
Some people say Q5 as a form of shorthand and some do it because they don’t know any better. Sometimes on the Chinese lights that might even be incorporated into the name. DX lists lights with no other name sometimes as Cree Q5.