I have an HTC Evo 4G phone and I didn't even know the Lux Meter app was available until today. I downloaded two different ones and both have a max reading of 10240 lux. Both by EDC lights easily max this out when pointed directly at the phone. So I tried a ceiling bounce in the bathroom. The apps don't register anything from the ceiling bounce even though it is fairly bright in the bathroom. Are these apps junk? Anyone found one that works OK? Thanks.
I've had exactly the same... I've tried 2 android apps, both go to a max of 10240, and that's it. When I point my TK566 direct to it, the max gets reached, even at the low-mode. It's either the apps or the meter in my HTC HD2 is just not good enough...
The apps won't register anything that's not pointed directly to them.
I use one on my iphone 4 and it's pretty good..it's free and called "light meter"..it isn't as precise as a luxmeter from what I gather from using it but it is what it is lol
A little off topic but does anyone know how I can use my cameras sensor as a light meter? I have a Canon T2i if that makes a difference at all
Interesting idea. Do you point the light at the camera or at the ambient light sensor on the phone?
Mine picks up the light from the tiny camera lens that is on the front of the phone (the regular camera lens does not work for this purpose).
Yes SB, it uses the ambient light sensor on the front. Atleast on my phone (droid incredible) its not very precise at all. The app is pretty much useless. It doesnt go lower than "40" (even in a pitch black room) and even the dimmest of lights pointed at it will make it hit the max. It didnt even register the light from a manafont xml dropin aimed at the ceiling in a tiny bathroom. Waste of space on my phone 
Ah, I would have expected the camera to have a better light sensor. I have a Droid 2 Global, and the ambient light sensor doesn't seem to work very well to control the screen brightness. It can basically detect total darkness, a lighted room, and glaring sunlight.
I have been thinking about that myself. Like how do I convert stops to lumens? What spot metering mode to use (probably one with the most number of control points)? Maybe TTL flash will work better?
The ones that worked for me are the beeCam lightmeter and lux meter. Values do scale, but almost linearly as the light is moved away from light sensor (so nothing like real meter at all). However, it is reasonably precise (but not accurate) so can be used for something in a pinch.
I use Luxus widget on my N900.
It seems to do a good job. I initially tried using it to directly measure the lux to get an idea of throw numbers, but the figures that came out were all over the place. Now I use it to measure reflective lux (ceiling bounce test) to get an idea of relative brightness between lights in my collection, and the test results are repeatable.
Whatever these apps are measuring, it certainly isn't "lux" despite what the label says. Even relative comparisons are suspect since a number twice as big doesn't mean twice as much of anything.