Mag85 over 20,000 lux?

[sygyzy]

I got a new light meter today, the LM631A. I measured from 1 meter in a dark room and took the max value. All of the lights I measured settled on a number after a few seconds. The Mag85, on the other hand, kept rising, even if as I held the flaslight still. Eventually it reached 20,000 lux and the displayed showed it was overloaded.

All of Meterman's light meters max at 20,000 lux. First of all, is this an accurate reading or did I do something wrong? Is it really 20,000 lux? My next closest light is the Pelican 7060 LAPD which is 8430 lux. Nothing else is even close. How does anyone measure a Mag85? Are you guys using better meters?

 

[Patriot]

Yes, the 85 could be over 20,000 lux and even many of the LED throwers measure between 20,000 and 30,000 lux. Most of us use 200,000 lux max light meters though.

 

[2xTrinity]

I got a new light meter today, the LM631A. I measured from 1 meter in a dark room and took the max value. All of the lights I measured settled on a number after a few seconds. The Mag85, on the other hand, kept rising, even if as I held the flaslight still. Eventually it reached 20,000 lux and the displayed showed it was overloaded.

All of Meterman's light meters max at 20,000 lux. First of all, is this an accurate reading or did I do something wrong? Is it really 20,000 lux? My next closest light is the Pelican 7060 LAPD which is 8430 lux. Nothing else is even close. How does anyone measure a Mag85? Are you guys using better meters?

measuring the lux at 1m isn't an accurate way to judge the intensity of your light. Only if your light is an ideal point source is Lux at 1m equivalent to Candela (angular intensity) output of your light. When you are close to your light, the light is being emitted from the whole bulb + reflector system, NOT a tiny single point in space. Different reflectors may be biased to give high number AT one meter, but not actually be more intense at distances greater than 1m (which is what matters for a thrower).

The best bet is to take the light meter as far away from your Mag85 as possible, while still having enough intensity to take a good reading. At a greater distance, your light will start to look and behave more like a point source, and you can use the inverse square law to calculate the "equivalent" lux @1m (that is, what lux @ 1m would be if your light were a point-source). This is the same as the candela, or intensity of your light into a given angle.

Try measuring the intensity at 10m, then multiplying by 100, and see what you get then. If you read 220 lux @ 10m, then that is 22000 lux @1m. If you read more like 180, then that means your 1m reading was exaggerated because of your Mag's reflector geometry. You could even try 20m away and multiply by 400. Beyond a point you'll start to push the sensitivity limit of your meter, so as far away as possible, where you still have enough light to get an accurate reading is best.

 

[sygyzy]

Thanks for the tips guys, especially you 2xTrinity. I did not know about that trick!

Patriot36 - Could you recommend a 200,000 lux meter? What do you use?

 

[Patriot]

Patriot36 - Could you recommend a 200,000 lux meter? What do you use?

Mine is a cheapy from DX. I think it was $28 + shipping. Trinity's method works too. I usually measure mine at 10M anyway.

 

[sygyzy]

My apartment is not big enough to measure at 10M. Could I measure at 5M and multiply the result by 25?

 

[Patriot]

Yes, any distance will work as long as you use the inverse square law.