Light Meter ~ Lux Reading Troubles.

[jtice]

I just got a Meterman LM631 Light meter today, and was taking a few readings of lights I own.

I am beginning to think that it is not accurate. /ubbthreads/images/graemlins/frown.gif

I have the meter laying on the floor of my pitch black bathroom, about a foot from the wall.
On the wall, 1 meter high (actually, 1 meter, plus an inch, to compinsate for the height of the light meter sensor off the floor)
I hold the flashlight about a foot out from the wall, using the mark on the wall as a mark of one meter away, to hold the light in place, pointing straight down, shinning on the meters sensor.

I do as the directions say,,, leave the sensor cover on, turn on the unit, then take off the cover.
I set the meter to 10X (20,000 lux range) and set it to peak hold.

Here are some readings I am getting so far.

ProMagnum S Bin LuxIII 6AA == 6,800 Lux
TWAK Bin DB1227 mag 3x123 == 8,000 Lux
TWAK Bn Uflex set to 1000mA Mag mod with 8xAA == 7,000 Lux

Heres the real odd one,,,,
Arc LSH-P fresh batt == 322 Lux

The LSH-P should be around 500 Lux, says www.flashlightreviews.com

Any advice? Am I doing something wrong?
What are your proceedures for taking Lux Readings?

Most of you have seen my light collection,,,
know any Lux readings for any of the lights I have?
I will test that perticular light and see what it says.

Thanks alot guys.

-John

 

[jdriller]

Your readings are on the money. I got 320 for my LSHP /ubbthreads/images/graemlins/grinser2.gif

My Yukon HL readings were very different from the site. You know the saying "Luxes vary"

 

[Kiessling]

I got 354 for my Arc, and this was a modded one at 363mA with an R2H, your value sounds good to me.
I also get very high numbers on well focussed beams (obviously), I think a DB917 / PR combo was about 4000 or something ... so ... I do not see anything wrong here.

On the other hand, I am the biggest greenhorn in this matter myself /ubbthreads/images/graemlins/grin.gif, so you might want to listen to someone who actually knows /ubbthreads/images/graemlins/smile.gif

bernhard

 

[Sway]

Thats sounds about right are you running the sputter in your ProMagnum? If so it will cut down on your Max Lux reading swap it out for a standard refelctor and you will see a higher reading /ubbthreads/images/graemlins/grinser2.gif

Later
Sway

 

[kj]

As others said, your numbers seem reasonable. I got 300 lux for LSH-S and 390 lux for LSHF-P and I believe LSH-P should be around them. I also have DB1500/TV1L/Mag2C and, IIRC, I got around 10,000 lux.

 

[MR Bulk]

Your Arc reading seems okay (I don't have the other lights).

 

[jtice]

Thanks guys,

After playing with it alittle more, I think its doing ok.
I did multiple readings for each light, and it was fairly consistant, with the DB1227 mag dropping each time, which makes sence.

Sway, its a stock smooth mag reflector, so I expected the Promagnum readings to be alittle higher. It has about 10 minutes of runtime on it, so it should still be pushing near full brightness.

Good news? It takes ALOT of Lux, before the human eye can see the difference. /ubbthreads/images/graemlins/wink.gif

 

[Quickbeam]

Hmmmm... wonder if MY lux readings are a little off... Or perhaps I just got lucky in the Luxon Lottery with the ARC LSHP.....

OK - just re-checked the LSHP - at one meter 326 LUX. Looks like I must have goofed when I took the reading. I'll adjust the review - the charts will come later.

Ticey: You're on the money! /ubbthreads/images/graemlins/thumbsup.gif

 

[gadget_lover]

Gotta keep in mind that when reading LUX, the reflector/optic have as much to do with the reading as the light source itself. The ARCs should be fairly consistant, as they were assembled teh same way with the same optics.

You will get lower readings if, for instance, the optic is not reasonably centered. You will also get lower readings if the optic or lens is dirty. Using a big parabolic reflector will create a hot spot that is very bright.

Darn, now I have to check mine /ubbthreads/images/graemlins/smile.gif

Daniel