Anyone with a luxmater who want's to share their measurements...

It's friday! I do not work on saturdays and sundays so it's free time!

I decided to pull my luxmeter out of drawer and start to use it.

I did some measurements and anyone who wants is kindly asked to post their info for the sake of comparing the results. Nothing really alot meaningfull but it can be fun.

Later on i have to build myself something along the line of an "integrating sphere" for trying measuring lumens.

Test method:

Floor setup of luxmeter, fresh battery, measure tape offsetted by luxmeter height from floor level and exactly 1 metere from the flashlight lens (give or take a very few mm of the margin of error).

Fully charged hi-max 18650 li-ion for li-ion capable flashlights/dropins

10 seconds reading trying to catch a best possible readout on the luxmeter.

the luxmeter itself (photo stolen from net from somewhere):

My candidates and their respective readings:

Q5 based Ultrafire C3 SS on max with AA Eneloop - 2112 lux

R2 based uniquefire hs-801 on max: 33400 lux

R5 XTAR D01 diving flashlight on max: 13300 lux

R5 p60 dropin 5mode (MF) SMO reflector at high: 8390 lux

XM-L p60 dropin 3mode H-M-L (MF) SMO reflector at high: 5390 lux

Q5 p60 dropin 1mode at max (DX) OP reflector: 7920 lux

Now i'm interested how similar results can be had considering the cheap luxmeters accuracy, emiiters, reflectors, lenses, drivers, exact distance can all affect measurements.

Nice luxmeter. I figured out that I got more real results when I measure at the distance of 2 meters, and then multiple the value with 4.

Out of curiosity how do you know the real value?

Inverse square law - double the distance, quarter the output. But it is easier to detect the peak brightness in a larger hotspot.

At 3 metres the result will be 1/9 of the one metre value

4 metres: 1/16

and so on.

This also prevents saturating the meter's sensor.

Sigh... so i best redo the test with 2 or 3m and calculate the readings?

Not really necessary but it should give better results.

Just to add to the fun you should be measuring from the emitter, not the lens. I use 1 metre measurements as the underside of my desk is exactly one metre from the floor - it is easy to line up the emitter with the bottom of the desk.

Small errors in positioning are much less important when the distance is larger, but I don't have a 2m high desk.

Eeeew!

I sell a luxmeter cheap! anyone?

Joking aside, good info... one never stops to learn.

I 'd love to take part to this experiment this weekend but my lux meter should be on my hands on Monday (HKP says). So I will try to follow next week.

I can give anyone who wants edit rights to the lights spreadsheet where we can put up our measurements. If everyone has a tab of their own, we can sort out variations between measurements where we have the same lights to compare.

Or I can take the results from here and put them up on a tab in the sheet in my sigline. Whatever is easier for people.

Nice idea.

That's a great idea Don. You've just motivated me to get an inexpensive meter and start playing this game. Any recommendations on a meter?

Mine is certainly not a lab-grade device but it was affordable. I got this one

http://www.dealextreme.com/p/50000lux-2-1-lcd-digital-light-meter-20170

Quicky:

Lux Flashlight

15000 Aurora SH-40 SST-50 (pleasant surprise, body looks like KD C8 but it has a deeper smooth reflector and perfect beam)
10200 MF XML Dropin
8500 KD C8 (xml) - 18650
8000 Aurora AK-P7
6500 KD XML Dropin (it has a donut hole which makes it very hard to measure, in reality it is a good dropin)
4000 iTP A1 eos (r2) - 16340
3000 Palight SS (xpg) - 18650 (compact)
550 iTP A3 eos upgraded (q5) - alcaline (old - used alcaline)

14000 edi-t (p4) - 18650 (FTT zoomed in)
14000 edi-t t11 - 16340 (FTT zoomed in)
13000 lichao lc-007a (q5) - 18650 (FTT zoomed in)
8800 romisen rc-c6 (FTT zoomed in)

Lux meter: http://www.dealextreme.com/p/digital-lux-meter-with-stand-200000lux-5100

Numbers are somewhat rounded as I am playing for the first time with a lux meter and this play isn't really that scientific.

All measurements are on 1 meter.