Lux meausrements

[andrewwynn]

I recently acquired my first light meter. I know that most standard measurements are at 1m, but it's a much more boring level on the meter of course.. i've seen a lot of pictures at 1'.

I did a couple quick tests with lights i had on hand.. all at 1'

nano low: 180
nano med: 530
nano high: 810

ARC LS with 2x AA: 1550
ARC LS with 1x LiON AA: 3250

but.. I've been waiting months to do this test:

My micro 27 measured 21,000 lux at 1 foot.

Can somebody point me to some other lights for comparison.. and if they are 1m vs 1'.. i can re-do mine.

i didn't write it down, but i think that megasonic measured 35,000+ at 1'

 

[MR Bulk]

...and some lights can hit a million or more from one inch! I'd stick with the standard - take readings from one meter away (about 39-3/8"). That way we all compare apples to apples...

 

[MR Bulk]

...or switch the meter to f/c (foot-candles) to measure from a foot. You'd get the same numerical reading as from a meter away in lux.

 

[andrewwynn]

I like the foot-candle idea. it's much easier to hold something 1' away.

that makes the nano read 16, 45, 80 fc @1ft and the micro27 reads 1800.

 

[andrewwynn]

too funny.. i was going to email you directly but didn't want to bug, so i posted and you replied anyhow.

 

[gadget_lover]

A valid use for the even closer (1 inch) readings is to detect minicule variations in output. Many meters have only 1 fc resolution, so it's hard to see minor changes.

Daniel

 

[evan9162]

For general brightness (throw) measurements, I'd suggest we move to measuring lux at 2 meters. My reason for suggesting this is that I've noticed that many beams (especially from a Mag reflector) aren't completely coherent/formed at 1m, but are much moreso at 2m. Basically, the measurements I've taken at 2m are greater than 1/4 of that at 1m (inverse square law and all), but measurements past 2m and beyond do follow the inverse square law.

 

[Doug S]

[ QUOTE ]
andrewwynn said:
I recently acquired my first light meter. I know that most standard measurements are at 1m, but it's a much more boring level on the meter of course.. i've seen a lot of pictures at 1'.

I did a couple quick tests with lights i had on hand.. all at 1'

nano low: 180
nano med: 530
nano high: 810



[/ QUOTE ]
Andrew, are those with the stock brass reflector, your handground parabolic brass, Nickel plated stock, or handground nickel plated? Known bin emitter?

 

[andrewwynn]

hand-ground brass.. 'copy chromed'.. not 100% sure on emitter.. T**J i think.

 

[Kiu]

For comparing the throw, I will even take the lux reading from 7meter.

 

[andrewwynn]

i don't think i have a 7m range of darkness... but i will try to make measurements at several distances.. my current project it flood more than throw, so i won't be needing any 7m measurements, but my micro27 light (about 5W into a 27mm IMS).. is so mind-blowing bright.. i can throw 50-80 meters no problemo.

-awr

 

[PeterW]

I use a cheap IKEA 1m paper tape and put the meter on the floor and point the light down at it, wiggle it about to get the highest value and bingo. I agree the detector is quite larg with repect to the beam as 1meter and so very sensitive to positioning when getting the 'correct'value.

I like using my meter to confirm my hunch that my lights have got dimmer and need a battery change..... you just get used to the slow dimming, you don't notice it.

Cheers

PEterW