Light Meters

**DONOTDELETE** · #1 11-02-2001, 05:16 PM

Where can I buy a reasonably priced meter to measure light output of my flashlights etc..

Thx,
007

Artie Choke · #2 11-02-2001, 07:37 PM

check out this thread - there's one for $34 a number of people have bought.

lux meter

**DONOTDELETE** · #3 11-02-2001, 07:52 PM

Many Thanks Artie!

007

**DONOTDELETE** · #4 11-03-2001, 06:57 AM

Is there a formula that converts the reading from lumens to candelas???? i.e. how do you convert the meter's reading to interput the power of the light?

Thx,

Artie Choke · #5 11-03-2001, 11:10 AM

gack! (as bill the cat would say [img]images/icons/smile.gif[/img])

there's some threads about the different light measurement units. search for lux, candela and/or lumens and you'll eventually come across them.

there's also a (very) technical light measurement handbook on the web (thanks to quickbeam for the link) - check out this chapter (scroll down to the section called Irradiance and Illuminance):

light handbook - measurements

if i'm reading it correctly:

1 lm/m2 (lumens per square meter)
= 1 lux (lx)
= 10-4 lm/cm2
= 10-4 phot (ph)
= 9.290 x 10-2 lm/ft2
= 9.290 x 10-2 foot-candles (fc)

so 1 lux = .09 candela - but it's probably not that simple.

i think lux and candela are simlar measurements, just done at different distances. lumens is a whole different ballgame! [img]images/icons/shocked.gif[/img]

**DONOTDELETE** · #6 11-10-2001, 09:54 AM

1 lux = .09 candelas - does this work to get a rough estimate of torch output?

**DONOTDELETE** · #7 11-11-2001, 11:05 AM

Craig, would love to see the chart.

Thx [img]images/icons/grin.gif[/img]

Chris M. · #8 11-11-2001, 02:34 PM

but I don't know how to do tables which would be necessary in order to post it on the web.

I`d be happy to help here- Craig, send me an email- tables are surprisingly easy to do once you`ve got hold of the basics.

[img]images/icons/grin.gif[/img]

The_LED_Museum · #9 11-11-2001, 10:58 PM

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Artie Choke:

1 lm/m2 (lumens per square meter)
= 1 lux (lx)
= 10-4 lm/cm2
= 10-4 phot (ph)
= 9.290 x 10-2 lm/ft2
= 9.290 x 10-2 foot-candles (fc)
<HR></BLOCKQUOTE>

For illuminance measurements:

To obtain footcandles (lumens per square foot), multiply the lux reading by 0.0929, or the phot reading by 929.

To obtain lux (lumens per square meter), multiply footcandles by 10.76, or phot by 10,000.

To obtain phot (lumens per square centimeter), multiply footcandles by 0.00108 or lux by 0.0001.

There are also other measurement units with names like blondel, candela, footlambert, millilambert, nit, and stilb. I have a conversion chart for all of these in relation to one another, but I don't know how to do tables which would be necessary in order to post it on the web.
Maybe I'll just try to take a picture of the thing.

**DONOTDELETE** · #10 11-24-2001, 05:30 PM

Would this type of meter also be able to measure laser lights - like Stingmon's green super-duper laser pointer??? [img]images/icons/confused.gif[/img]

**DONOTDELETE** · #11 11-27-2001, 03:56 PM

Thanks go out to Ted the Led

The Dude [img]images/icons/smile.gif[/img]

**DONOTDELETE** · #12 11-27-2001, 10:16 PM

I copied this from AlexGT when he posted it some time ago here; thought it might come in handy some day, did it?
----------
"...If the calculations of the MasterConverter¥s software are correct here are the conversions for Lux of the different leds.
White: 54 Lux equals
5.01676416 Lumens/foot2
54 Lumen/meter2
7.906295754E-6 Watts/cm2

Red: 310 Lux equals
28.7999424 Lumens/foot2
310 Lumen/meter2
4.538799414E-5 Watts/cm2

Blue: 70 Lux equals
6.5032128 Lumens/foot2
70 Lumen/meter2
1.02489019E-5 Watts/cm2

The Yellowish white : 181 Lux
16.81545024 Lumens/foot2
181 Lumen/meter2
2.650073206E-5 Watts/cm2
Regards!
AlexGT ...."
------------
I don't know about measuring the green laser.. [img]images/icons/confused.gif[/img]

Quickbeam · #13 12-10-2001, 04:31 AM

I ordered one of the $35 lightmeters, so my reviews will soon include light output readings. I'll let you all know how it goes with the new meter.

**DONOTDELETE** · #14 12-10-2001, 07:37 AM

[img]images/icons/smile.gif[/img] Quickbeam, I look forward to your findings... Thx Dude

Quickbeam · #15 12-11-2001, 06:28 AM

Bad news. The $35 light meters are out of stock for 3 months... [img]images/icons/frown.gif[/img] [img]images/icons/frown.gif[/img] [img]images/icons/frown.gif[/img]

Quickbeam · #16 12-12-2001, 04:58 AM

Well, yesterday I went surfing to try to find the $35 meter elsewhere and found it a familydefense.com for 49.95. I sent an e-mail to see if they would pricematch. They said no. I did mention that the other retailer was out of stock but would be getting more in.

Here's the rub: I went back today and they jacked the price up 10 bucks! Now it's 59.95 each! Looks like they decided to try to take advantage of the fact that the other retailer is currently out of stock. Needless to say, they won't be getting my business at that price. Lux ratings on my lights will have to wait. Sorry folks.

Quickbeam · #17 12-13-2001, 07:32 AM

The lux readings for my lights will be starting soon! I did order the lux meter from familydefense.com. They honored the $49 price I saw. Even at 59.95 it's still the best I can find on the web for this unit.

Also found out a possible reason for the really low price on the the other retailer's page. It's quite possible those meters are factory refurbished customer returns - hence possibly why some people got dead batteries with them. Perhaps not, but it would make sense. Of course, if they work fine, who cares?