Lux Meter recommendations

Hi all hoping for a bit of advice on lux meters , looking to buy a reasonable ish one but nothing super fancy

Ive seen them available in 200,000 300,000 & 400,000 lux not sure what i actually need for modern flashlight testing ??

From what i have read 1 lux @ 1 meter is pretty close to a Candella so to read something in the upper Kcd-Mcd ranges it needs to be able to read close to a million lux?

this one for example can only go to 200,000lux which i dont think is anywhere near high enough, this tops out around 200kcd right?

You don't need to measure at 1 meter, and usually it renders wrong values due to non fully focused beams. Take a read at illuminance (lux), luminous intensity (candela) and ANSI-NEMA FL-1 (beam distance or throw) if you wish to understand. Here it is if I'm not mistaken, nearly made my mind :-P a mess with it again:

(beam distance)² × illuminance = luminous intensity

Given the above, if you measure at 8 meters and get ≈8 Klx, that equals 512 Kcd.

Thanks Barkuti, appreciate the detailed reply and will have a read of those links, I’d just like to be able to get some numbers for the flashlights i’ve modded and be able to make comparisons when trying different tweaks

So just to confirm

it is Beam distance Squared * Lux to get Intensity , so that little meter i picked out on my first post would probably do fine for this

Indeed and indeed. More expensive meters will also give more accurate readings over a wider spectrum of light tints, CRI and etc. Or so they should, maybe you could ask djozz for a lux meter recommendation as he is pretty experienced in these matters.

Problem with luxmeters is that there is a gap between very cheap lowish performance and very expensive good performance.

For a start, giving ok ballpark numbers I’d go for a Uni-T UT383, 16 dollar on Banggood, also very cheap on aliexpress. It works and is not grossly off.

Thanks again guys, I just had a look at the Uni-T UT383 and saw they also do a Uni-T UT383s for just a few bucks more same meter but with remote sensor. thanks for the recommendation.

I tested two Uni-T luxmeters (follow links in my sigline) and they had completely different internals and measurement characteristics (the more expensive one had really horrible performance). I have not measured this specific one, the naming suggests it is like the 383, but you never know for sure until someone tests it. That said, my feeling is that you should be ok with this one.

Is this one ok ?

That’s the one I have.

Just to get a sense of comparison between your various lights, it works just fine, IMO.

Guess ill take the chance, when it arrives i will get some photos of the PCB & sensor and send them your way , perhaps you’ll be able to tell if its the same unit… Hope so but you how it is with these products even later versions of the same model can have different internals :-/

It looks like one that I tested, not very good on spectral accuracy, it gives fairly large errors for tints that are well away from what it is calibrated at. (test via my sigline link)

I have the 383s, ive tested it against lights with known output, its quite good, within given specs

Thank You for that advice. I cancelled that order, LOL. :+1:
Is there a light meter made that is affordable ? Any suggestions are welcome.
Just going to use it on flashlights.

i use Dr meter 1330B its not expensive at all and goes to 200,000 lux. If you are planning to measure lumen levels, the readings may be off the charts if your light box is too small. But if you add some pvs pipe with elbows that is going to absorb some of the light and the flux you end up with will be ok to measure even 20,000 lumn lights. At first i thought this absorption is going to render inaccurate results but my results are quite consistent across different lights.
If you are measuring how far the lights will throw, the meter will be ok for throwers up to about 1000 meters even if the light source is measured from 1 meter away . With stronger throwers you can always move th source further out and recalculate. So i would recommend this meter

Many people are using the DrMeter, but the fact that it is widely used and is nice to work with does not tell you that it is very accurate. It is fine for most what we want as a flashlight user, namely measuring light a bit better and consistent than what our eyes can do. But if you want trusted measurements of lux/lumen across light sources of diverse tint (and CRI), the Dr.Meter does not do that so well, while the even cheaper Uni-T UT383 does that a littlebit better (but still not very good).

Wow, after further reading and research is there any light meter that is affordable and with any degree of accuracy ?
You would think that pointing a flashlight at a light meter would not be that complicated, but yes it is.

:weary:

It is complicated to measure light at even a 10% accuracy and that is not just us hobbyists, the whole lighting industry struggles with that. It needs expensive equipment and strict procedures to do it right, and most people do not realise it.

Luckily, in light output assesment, our eyes are far worse than even the cheap luxmeters that we use so in the end any accuracy is wasted on us humans: we will not notice.

I’m afraid anything that’s ‘affordable’ is not going to be very accurate, but again, if you’re just using it for home hobby purposes, IMO any of them will do.

I tested one Extech meter, not the cheapest from that brand, that performed fairly well on both calibration and spectrum sensitivity, but I assume that their whole range uses the same sensor/filter combination so should be as good. But you are talking well over 100 dollar then.

Exactly this!
Our eyes are actually very unreliable, everyone has a different sight.