L4 runtime discrepancy

[brightnorm]

There seems to be more than 30 minutes difference in L4 regulated runtime between kj’s chart and Roy’s. I’m not sure how to interpret this.

kj:

Roy:

Brightnorm

 

[kongfuchicken]

kj's L4 runs for a tad below 50 minutes; roy's L4 runs for a tad over 50 minutes...
Where do you see a 40 minutes difference? /ubbthreads/images/graemlins/icon3.gif

 

[brightnorm]

In Roy's chart the vertical lines mark 15 minute intervals and the runline goes past the 5th vertical line to just shy of midway between the 5th and 6th line (1:15 and 1:30), which is about 1 hr and 21 minutes for a difference of roughly 34 minutes from kj's figures. I don't know how to account for such a large discrepancy.

Brightnorm

 

[Roy]

Before anyone asks....I used Surefire batteries. I don't think there would be THAT much difference between battery batches. I have no knowledge of how much differences there can be between led's, but I doubt it would amount to 35 minutes.

It would be interesting to see another runtime plot on a third L4. It might indicate which light is the unusual light!


ADDED

I just noticed that kj's Surefire plot starts a 860 LUX and mine starts at 547 FC @ 1Ft! My 547Fc @ 1Ft should be equivalent to 547 LUX @ 1M. If kj's measurment was at one meter then the answer to the difference in runtime is easy to account for.....his light is 313 LUX BRIGHTER than my light. He used up his batteries faster than I did.

 

[kongfuchicken]

my bad I thought the lines were 10 minutes intervals...
I'll read before I post next time.
Interesting indeed.

 

[brightnorm]

[ QUOTE ]
Roy said:
...his light is 313 LUX BRIGHTER than my light. He used up his batteries faster than I did.

[/ QUOTE ]

Roy,

This is confusing, I thought an L4 was an L4. My three L4s have nearly identical brightness and I seem to recall reading that they normally pull around 650ma, though I can't be certain. Was his L4 modded?

Brightnorm

 

[brightnorm]

Surefire is known for its conservative specifications so the following excerpt from their L4 page leaves room for question:

"The L4 produces 65 lumens of light for over an hour, followed by lower output for over two hours. Unlike most LED flashlight manufacturers -- who inflate the light output and usable runtimes of their LEDs -- SureFire provides realistic output and runtime specifications based on scientifically obtained measurements."[/b]

Brightnorm

 

[brightnorm]

It would be interesting to have a third runtime test for comparison. Anyone?

BN

 

[BC0311]

I'm interested, but clueless. /ubbthreads/images/graemlins/yellowlaugh.gif

/ubbthreads/images/graemlins/popcorn.gif

 

[bagman]

I have not done a run time test on my L4 with 123a's cos I'm tight like that /ubbthreads/images/graemlins/wink.gif but I get just over an hour, 63 mins IIRC, with both of Pila 168S's I bought for it.

 

[kj]

My L4 is in the stock condition, not modded. I measured the lux with LM631 at 1 meter.

I don't know why the Roy's runs longer than mine, but this is another example for your reference. According to this chart, bon's L4 runs 60 minutes in regulation.

 

[brightnorm]

Thanks for that chart

BN

 

[kj]

I asked bon and Silver Legacy to measure my L4 at their measurement environment and got the following results.
<ul type="square">Who's L4? . . Measured by . . Lux at 1m . . Lightmeter
---------------------------------------------------------
bon . . . . . . bon . . . . . . . . 450 . . . . . . See this picture
kj. . . . . . . . bon . . . . . . . . 630 . . . . . . See above
kj. . . . . . . . kj . . . . . . . . . 800 . . . . . . LM631
kj. . . . . . . . Silver. . . . . . . 760 . . . . . . LM631[/list]
According to the results, I would say:
<ul type="square">[*]My L4 is about 40% brigher than bon's L4.
[*]bon's lightmeter shows the lower (about 80%) lux reading than my LM631.
[*]Even with the same lightmeter, there are certainly some measurement errors (about 5% in this case).
[/list]