Cree lumen gain..is it useful for you in everydays application?

I believe I have too much an expectation for Cree as my recent experiences with the P1D CE and XR19C have told me. The expected lumen gain was not that useful for me. I need alot more lumen gain to really appreciate it. This scienario is similar to digital camera pixel gain. You need more than double to really makes a difference. What is your experience?

I think you make some good points, but the lumen gain is almost double, and alternately you can take the advantage in runtime, getting about 2x at the same total output. So IMO the improvement is useful (granted we are not the most practical/objective folk here when it comes to flashlights - right?).

Another consideration for me is that unlike computer/electronics, the rate of gain in performance for LEDs is not so predictable and steady, so the XRE improvement is very noteworthy. I expect there will not be another step change (~2x) like this - maybe ever.

Finally - the beam type is significantly different for the XRE vs a Lux3 or Lux5, so that can provide some usefulness as well. For example, I've found that pairing my A19 XRE (which I use with a 2 CR123 body for long steady high output) with my L4 (with two stage switch) gives a real power punch even though the total output is similar. One for a "wall of light" with major flood / area illumination and general use, one for "practical throw" - good throw combined with good spill for spotting distant objects.

Is the output of the P1D-CE on low (using CR123A) more useful than the output of the P1D on low?

The gain is in efficiency. Who would be against that?

If that translates into more lumens, why not?

Many of these lights are coming out with multi-stage output. It's there if you need it, can be skipped if not.

LA OZ said:

I believe I have too much an expectation for Cree as my recent experiences with the P1D CE and XR19C have told me. The expected lumen gain was not that useful for me. I need alot more lumen gain to really appreciate it. This scienario is similar to digital camera pixel gain. You need more than double to really makes a difference....

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Your experience is consistent with how the human eye works. We don't perceive brightness in a linear fashion, but rather logarithmically. This is more similar to how we perceive sound. That's why sound meters typically display in db, not a linear scale.

The confusion comes from lux meters often having a linear scale. Double the brightness, and the meter reads twice as high. Likewise flashlight reviews post lux and lumen numbers (or similar).

You often hear statements like: "light A is 30% brighter than light B", etc. That only means a 30% MEASURED difference, not a 30% VISUAL difference. Yet it can imply a significant visual difference should be apparent, but it's not.

Lumen increases are not like horsepower increases in a car, where a 20% difference is perceptible in a major way. Lumen variations of +/- 20% or 30% are barely visually significant.

The XR-E's 2x gain in MEASURED brightness at the same power level is a tremendous advance. You can use that to achieve either 2x the MEASURED (not VISUAL) brightness, or 2x the run time, or a combination. But 2x the MEASURED brightness won't appear VISUALLY 2x as bright.

The apparent VISUAL brightness difference is roughly approximated by Stevens' Power Law, the quotient of the cube roots of the two levels: http://en.wikipedia.org/wiki/Stevens'_Power_Law

Assuming two identical beam patterns, the apparent visual brightness difference between a 100 lumen light and a 200 lumen light is:

100^.33 / 200^.33 =
4.64 / 5.85 =

0.79, or

the 100 lumen light would visually appear 79% as bright as the 200 lumen light, assuming identical beam patterns and tint.

The huge advantage of the XR-E is more easily seen when expressed as run time. Unlike brightness, we perceive time linearly.

E.g, compare the Fenix P1D CE to the HDS U60XR. The P1D CE "primary" output is about equal to the HDS U60XR in "maximum". Yet the P1D run time at that level is an incredible 2 hr 42 min, compared to the U60XR 37 min, both using the same battery type. Considering the U60XR is the extended runtime version using a hand-picked emitter, the P1D CE constitutes a tremendous advance.

P1D CE review: http://www.flashlightreviews.com/reviews/fenix_p1d.htm
HDS U60XR review: http://www.flashlightreviews.com/reviews/hds_edcu60xr.htm

Is 40mpg better than 20mpg? Argument over IMO...

LA OZ said:

I believe I have too much an expectation for Cree as my recent experiences with the P1D CE and XR19C have told me. The expected lumen gain was not that useful for me. I need alot more lumen gain to really appreciate it. This scienario is similar to digital camera pixel gain. You need more than double to really makes a difference. What is your experience?

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I would rather 2x the runtime over 2x the lumens. I don't have problems with my LED flashlights not being bright enough for the way I use them. So, the extra runtime and less heat would be better for me and probably most users.

PWM is a problem at low brightnesses, especially for Cree - the lumen gain you would get with constant current is significantly higher than that you get with PWM.

SpeedEvil said:

PWM is a problem at low brightnesses, especially for Cree - the lumen gain you would get with constant current is significantly higher than that you get with PWM.

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What are you talking about with regards to the PWM? You can PWM any LED without problems. It is actually the preferred way to dim a LED if you don't want color shifts. You just have to keep the PWM frequency up.

I haven't seen any data to suggest that a 10% PWM @350mA gives less luminance than a 100% PWM @35mA.

Newbie posted such data in a thread that I mistakenly said PWM when I meant switched mode power supply, in his testing (machine only, a "visual" experiment was mentioned as a future possibility which I look forward to hearing about if it happens).... anyhow, in the machine testing, PWM was consistently slightly less efficient than current regulation for a given level, although it was just a shade less (a couple percentage points) if I remember correctly. In other words, both work, and I don't think color shift was a consideration in that test, which is an interesting point that hadn't occurred to me while we were discussing PWM as a result of my misstatement.
Not sure why it popped up into this thread though, but Crees are tremendously efficient at low drive currents (and brightness), no testing I've seen indicates any probelms with PWM down to minimal drive levels, but also nothing to be gained if you can get an efficient constant current source for the same desired brightness.

Stereodude said:

I would rather 2x the runtime over 2x the lumens. I don't have problems with my LED flashlights not being bright enough for the way I use them. So, the extra runtime and less heat would be better for me and probably most users.

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Mmm, I'd love to see a SL ProPoly Cree 4AA with an 8-10 hour run time. They already confuse people with 3 different lights in the same body, might as well make it 4.

Bradley

Looks like a useful gain to me

I recently got the D-Mini from Lumapower, but I keep on using my Fenix L2T for EDC, since the cree is really too powerful for most of my everyday uses for a flashlight. Lit up the D-Mini too see better when trying to remove a small splinter of wood from a friends finger...bad idea, the thing made me see stars for minutes even after being reflected from his hand at 1 ft distance.....But like everyone is saying, turn down the power and gain runtime!!

New Cree Huntlight has five levels - and leaves most of the competition in the dust.

bguy said:

Mmm, I'd love to see a SL ProPoly Cree 4AA with an 8-10 hour run time. They already confuse people with 3 different lights in the same body, might as well make it 4.

Bradley

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I would buy that light! Er, um, well, I would think about buying that light and wish I had the money for it...

I think its even more interesting to see the side-spill with the Cree. Brighter, bigger hotspot, PLUS side illumination. Good stuff!

woodasptim said:

Looks like a useful gain to me

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heh but cameras play with exposure to get those shots not like an eye exactly

frasera said:

heh but cameras play with exposure to get those shots not like an eye exactly

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and Joema in post #5 make a point and it explains a few thing in my observation. My brain cannot discern significant gain when I use each Luxeon and Cree alone. The better run time is noticeable though.

Stereodude said:

What are you talking about with regards to the PWM? You can PWM any LED without problems. It is actually the preferred way to dim a LED if you don't want color shifts. You just have to keep the PWM frequency up.

I haven't seen any data to suggest that a 10% PWM @350mA gives less luminance than a 100% PWM @35mA.

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https://www.candlepowerforums.com/posts/1716762&postcount=63
For one LED - 75lm/W at 350mA, 110lm/W at 35mA (about).
Or another way, to get 7.5lm, you need an average of 35mA, if you pulse it, or 20mA if you don't.

My brain can tell the difference between a Cree and a Lux III when I compare the 2 together in the Streamlight 2L 3W which is also PWM. The Cree mod Streamlight is extremely bright where it actually hurts your eyes at a close distance compared to the Lux III is comfortable to look at, and the throw is almost double.

LA OZ said:

and Joema in post #5 make a point and it explains a few thing in my observation. My brain cannot discern significant gain when I use each Luxeon and Cree alone. The better run time is noticeable though.

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