I got my new lux meter today. how should I use it?

I have seen several different ways of using it. Should I be in a completely dark room? Also what is a distance most commonly used from the sensor?


Someone needs to write a proper guide on this.

You have the same meter a bunch of members have. Pretty good meter in my opinion.
If your trying to measure Kcd, generally you need to measure lights in a dark house or building or outside. You want to take measurements at different distances depending on the lights capability.
This is a general breakdown -
Lights under 50k - measure at 1m is fine
Lights 50k-100k - measure at 3m or more
Lights 100k & up - measure 5m or more if possible. Or the longest distance you can do accurately by yourself.
Make sure you use accurate distances for your testing, especially for very powerful lights. A foot can make a very noticeable difference.
Generally you don’t take your reading at the light start up. Most lights read high and some have a flare at startup. So give it a minimum of 5-10 sec before taking a reading. 30 seconds or so is best though.
Once you have that reading you need to calculate to the Kcd.
If a light is tested at 1m, then that is your true Kcd. If the reading is taken at longer distances, you simply multiply the distance times itself and then by the reading.
For example a 2000 reading taken at 5m. You go 5 x 5 = 25. 25 x 2000 is 50,000 or basically 50kcd.

That's a nice guideline Rdrfronty. I use the same approach. Only thing I can add is that if you get an unexpected result, measure at a different distance to verify measurement. As Rdr implied, use meters for the calculation.

Yes, using multiple distances is a good idea and I often do that. Especially on serious throwers. More tests and test distances help to eliminate possible errors, missing a hotspot, bad distance measurements, etc.

Great! Thank everyone!

I have a long weekend ahead and a lot of lights to test. Im excited!


I got basically the same meter, and I use it at the max distance I can fit in my home office, where it's dark, and I have an easy, quick setup for it. Not sure if reflected light is a factor or not, because the white ceiling is a little low. You don't have to be fully dark because low lighting usually won't even register on the meter anyway, so can't see how it would be a factor. From what I've seen, the meter readings follow what you see in outdoor comparisons, and I'm pretty confident my readings are good, maybe a bit low with some lights because of my short distance of 4.3 meters. I think it's generally (not 100%) agreed here 5 meters to 15 meters is where you want to be, if practical.

Just be sure to find the brightest point, not always the center - that's what most of us do. For me, a lot of times my best reading I can see in the first 15 secs, but I'll not use that - should be after 30 seconds. We try to follow the guidelines for ANSI/NEMA FL-1 standards, but of course that's not possible to achieve 100% without tons of $$$, multiple samples, and a lab controlled environment, but we just try to do the best we can with what we got.

You don’t need to test in a dark room. Just subtract the reading you get with no flashlight from the flashlight reading.