New & Confused Fenix LD10 R4 or R5 ?

I'm interested in the Fenix LD10 but don't know which is the best to buy, the R4 or the newer R5.

I've done a little research around the net and I'm finding reports that the R4 seems to have a brighter beam compared to the new R5. How can this be if its a newer model?

Any help appreciated.

R4 and R5 relate solely to the 'flux bin' of the led in the light, R5 by definition means about 7% more efficient (and so 7% brighter) than an R4 led.

I didn't think Fenix had changed the circuit or reflector between designs, which would also have an effect on overall output and/or perceived brightness, but maybe someone else would correct me on that.

I believe Fenix changed to the new ANSI measurement standards after R4. The R5 is indeed more efficient (and brighter, assuming apples-to-apples voltage/current), but the new measurement criteria makes it seem "dimmer". It is not.

PS - whenever a new bin is released, I am typically more concerned with the tint of the new offering more so than marginal lumen/lux increases. In this case, I prefered the color of the R4. Many R5's were very greenish in this light, IIRC.

My LD20 has the R5 emitter. It is a very cool white beam.

R4 has different circuit, emitter is driven much harder, that's why it's brighter. R5 has longer runtime though.

I'm pretty sure that it was just Fenix switching to ansi, which means lower output and longer runtimes.

I don't have an R5, but I do have the R4 and it's really nice. I love the tint. It's very hard to distinguish between med/high though. The difference in output can't be seen very well. At least to my eyes. You can see the difference between high and turbo though. I don't know how the R5 behaves in this regard. All in all, I'm sure you'd be happy with either version, because the LD10 is just a great light.

I have an R5 LD20 and find my tint to be cool white and not green. High and Turbo are noticeably different with turbo being brighter however I run mine with Enloops, and never with alkalines

Okay, thanks guys for the answers very helpful.

Found www.fenixlight.com LD10-R5 and LD20-R5 specs and different websites for LD10-R4 and LD10-R5 specs.
"R4" model historical stated lumens according to old Fenix methodology.
"R5" model stated lumens according to ANSI standard testing.

LD10-R4 Low 9, Med 50, High 105, Turbo 132
LD10-R5 Low 3, Med 13, High 45, Turbo 100

LD20-R4 Low 9, Med 50, High 105, Turbo 205
LD20-R5 Low 5, Med 31, High 81, Turbo 180

Hypotheses - Please confirm, expand, refute.
R5 higher flux than R4 for same given current.
LD10-R4 circuit drives much higher than LD10-R5 - Even turbo v turbo lumen claim doesn't seem merely ANSI adjusted delta.
LD20-R4 circuit drives much higher than LD20-R5 - Looks like runtime was maximized with reduced output.

LD10 / LD20, both R4 and R5 heads are threat compatible but not with older bodies.

LD10-R4 and LD20-R4 heads are interchangeable - battery count changes runtime and Turbo level brightness

LD10-R5 and LD20-R5 heads interchangeability unproven, but most likely interchangeable head with 8 output levels - 3, 5, 13, 30, 45, 81, 100, 180 based upon battery config?

Anyone tested the permutations?
Does the LD10-R5 on two cells behave as an LD20-R5 and does LD20-R5 on single cell behave as an LD10-R5?
Does the "R4" head fit on the "R5" bodies for a matrix of 13 output variations among them.

Somewhat academic as all R4 bodies have sold out.