I have an inexpensive lumen meter, cost around $15. I'd like to try to measure output from some led flashlights I have, but I'm not sure how to place it for measurements. It's sensor has a translucent white half globe, about 2" diameter. How far away should it be placed from the flashlight to give me a reading that might be compared with the claimed lumen output for the flashlight.
measuring lumens with a cheap meter
- Thread starter jbclem
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You need to homogenize the light to correct for different beam profiles - this is what an integrated sphere is for. Alternatively HERE'S a $5 BLF-style lightbox that works quite well. After that, you need to calibrate the lux readings to a trusted/known flashlight light/output to convert to lumens (well "brand X lumens" anyway), and can always just stick with relative readings without being sure what real ANSI lumens are.
There is only one reviewer here that claims accurate ANSI lumens using integrated spheres and laboratory tested calibration lights... if you have a few matching lights and can triangulate with him, you can get pretty close to real ANSI lumens.
There is only one reviewer here that claims accurate ANSI lumens using integrated spheres and laboratory tested calibration lights... if you have a few matching lights and can triangulate with him, you can get pretty close to real ANSI lumens.
mcnair55
Flashlight Enthusiast
Would it not be easier to read what it says on the packet that came with your torch.
Fireclaw18
Flashlight Enthusiast
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- Mar 16, 2011
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- 2,408
Sometimes the packaging isn't accurate.
About a year ago, someone showed me a light / phone recharger that had a single 5mm white LED as it's light source. This is the same kind of LED found in keychain lights that typically output around 10 lumens. However, the packaging for the light advertised that it was a "2000 lumen flashlight".
Measuring the output from a flashlight is not as easy as it sounds. I had offered to measure a prototype for a Kickstarter light and it was a pain (especially the moonlight mode). There are a lot of considerations going into a test including the calibration of the sphere/spectrometer. I ran the prototype through three spheres including a certified lab. This summary of the specs does a pretty good job of describing the test methods and issues: http://www.led-resource.com/ansi-fl1-standard/
If the link isn't allowed do search for FL1 standard. Good luck!
If the link isn't allowed do search for FL1 standard. Good luck!
