Help me use my light meter?

Off-topic Chatter
1

Hey guys i have had a light meter for a long time but i never bothered to use it so i thought i would try. I done a ceiling bounce test in my shed seeing as it is all the same colour roof and walls but the roof isn’t that high so there is only about a 1.5 meters to the roof where i am placing the light . I guess this will have no meaning for any one else but it may give me a slight idea how much brighter a light is compared to another light?
Also the shed is completely dark no windows and the doors are closed.

Would it better to do a lux test outside say at maybe 2 meters and point the light directly at the meter?

I have PVC pipping can i use that maybe seal of both ends? It is white in colour.

I know i am going to get good lumen readings but as a comparison with other lights i own this should work right?

The biggest variant would be the beam pattern if i choose either way of measuring?

I did do some testing i left the lights on for 30 seconds then done the measurements my new EDC gave me 37 lux and my old EDC gave me 30 lux. I placed them both in the same spots for the same amount of time.

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To compare output from two different reflectored lights, pointing the light at the meter won’t be accurate since it measures the intensity of hotspots. A flood light that’s 2000 lumens could have a drastically lower lux reading than a thrower that’s 900 lumens.

If you just want to compare different led’s in the same host, then you could use the lux reading from directly pointing the light to the meter to see if a certain emitter is brighter in the same host.

I don’t know how to make a light box to measure lumens so I can’t help you there. :cry: And I’m not too familiar with doing ceiling bounces.

For throw… (Assuming you don’t know how)

If you want to measure throw, set the light meter against a background that won’t reflect light. The ANSI standard at which distance from the light to set your meter are 2, 10 or 30 meters. I’ve read you choose the distance in which to set the meter depending on the reflector size, emitter choice etc. If it’s a thrower, you’d want to set it at a further distance due to the way a hotspot concentrates.

After you set up the meter and light, note the lux reading after 30 seconds and multiply it by 100. Then convert the lux to candela using a tool such as this:
http://www.rapidtables.com/calc/light/lux-to-candela-calculator.htm

To get throw in meters, read the last paragraph on this wiki and do the formula: http://flashlightwiki.com/Light_Output_Measurements#Throw

I created a spreadsheet that calculates the candela and throw distance in meters automatically when you input the lux, and the distance from the meter. It’s a very lazy way of doing it, since it’s easy enough to manually calculate throw and candela.

If you’d like, I could pm you the spreadsheet. I have other fun info on it like the percentage of lux dropped from the initial turn on, to after 30 seconds. Let’s me see if a light has better or worse heat management after soldering the mcpcb to the pill, or using another thermal paste. I can remove those if you don’t need them, and just send you the barebones file to calculate the candela and throw.