Big variations in lux numbers?

Stromberg

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First I want to say that I know already that different lux meters usually don't give identical results from same flashlights. There are differences in meter color calibration, test setup and in flashlights.

I just bought my first lux meter and I've been doing lots of measurements since then. What bugs me is that I keep getting significantly lower lux numbers than others who have measured same lights. For example Selfbuilt has measured (IIRC) 2500 from D20 and dude in light-reviews.com even 3570. All I get from my D20 is tad over 2000. Same goes for my D10 which gives about 1450 with fresh 14500 when light-reviews got 2630.

The lux meter I use is Reed Instruments ST-1300 http://www.tequipment.net/ReedST-1300.asp
And before everyone starts bashing the meter saying it's perfect poop, and that I should invest several hundreds to better meter, lets consider some other option first, OK?
The meter is calibrated to 2856K. I've done the candle test and it shows exactly 1 lux from one meter (dark room with no other light sources) as it should. Meter also seems to be very sensitive to even slightest variations in light so there is possibility that the meter actually shows lux numbers close to correct.

One ting I've noticed that if there is any reflective surface between the flashlight and the meter I can get several hundreds of lux's more. And because of this, I'll try to keep my test setup away from all surfaces. What kind of test rig are you using? Any other thoughts about the differences?
 

Stromberg

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Thanks chimo, I'll read those threads. In the mean time, if anyone wishes to share thoughts on this thread then you're very welcome to do so.
 

Stromberg

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That " Light Meter Benchmark Testing – CPF style" thread was very informative. I managed to find the same meter I just bought and if they are at least somewhat close together in measurement accuracy, my meter is quite ok. :)
 
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