My wild crazy ideas on metering and rating brightness.

My wild crazy ideas on measuring and rating brightness of flashlights goes like this;
1. Have a benchmark of what is brightness that anyone can relate to. (example: bright sunny summer noon)
Using a lightmeter I'll measure brightness of object at Nevada or Sahara desert at noon and whatever number meter comes out with shall be the basis for A1-bright.

2. Still at Nevada or Sahara desert measure light at dusk.
My intention is to have number from Lightmeter that I can easily relate to, not just for example no:2500 because the question of just how bright is no: 2500 will be hard to explain unless I have a understanding of bright which everyone understand and then relate it to a number.

This way we'll have a meeting of the mind when we talk about what is bright.

Measuring flashlights beam with rings can be complicated. My idea is to illuminate beam to a big white board at 20ft. Why at 20ft? Because I'm measuring useable light that is often in range used by man's eyes. 20ft. is my subjective estimate.

I'll measure the beam from its central hotspot going to the side and then rate the beam with notation on the size and meter reading on hotspot and its rings.

Well.... these are just some of my wild crazy ideas on measuring flashlights beam, please bear with me and be kind to me.

I agree 100% Edge, we need standard referances. I suggest a standard 60 watt General Electric home bulb since they are pretty much the same from bulb to bulb. And a chromed (chrome paint available at any auto parts store) Mc`donalds cup to measure total light output and standard distances from which to measure...1 foot...5 foot and 10 feet for example, to give use some idea of the beam spread. This way we could all adjust our meters to read the same and have the same results.

I suggest we all use whatever Craigs meter says the 60 watt measures at...say...1 foot with a light cup and adjust ours accordingly.

For lightmeter that don`t have screw adjustments, we would simply move the bulb closer or farther to the cup untill it reads the same and mark the distance as one. Maybe mount the it to a board for easey marking and adjusting with inch marks or mount it to a yard stick.

This sould also eleminate the reality that differant meters have differant pick up heads...some round...some squarish...some bigger...some smaller...ect


Once we all adjust our meters to read the same with the GE light bulb and identical light cups, we should all be able to compare light to light with similar results. At least in general...not perfect, but I think it`s the best we can do.


If folks don`t like the light cup idea we can trash it and just use meters. But we still need to set them up to read the same.. Any other idea`s?

KenB... light bulb is fine, how about raising the bench standard up by using a higher wattage bulb?

60-watt light bulb has yellowish color, brighter whiter light bulb will be better bench standard for say "A" level light, and other lights with yellowish color shall be in "B" or "C" group level.

Each level will then be sub-rated according to degree of color and intensity of lightbeams, example: A1, A2, A3, B1, B2, C4, D1.

All lightbeams with rings will go to lower level "C" or "D" regardless of whiteness and brightness. Smooth even beam of light gets "A" level rating and anything less gets lower rating.

Hey guys pitch-in what's in your minds.

The problem I see with using a 60 watt bulb or something similar is even a Photon will not read on that scale. This is the problem I am having with the brighter Surefire lamps. Even if I set a Surefire M6 away until I get a reading of 1000 (the highest the meter goes) then I get absolutely nothing even with an E1. I think I will have to set a distance, the 1 foot mark seems to be fine for LED lights, but I am guessing maybe 5 for the incandessant, and 20 for the Surefires.

I would like to meter them all by shoting them at a white screen then metering that, but again I get a reading of maybe 3 even with an Eternallight, so most of the lights read nothing that way.

Brock

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Brock:
The problem I see with using a 60 watt bulb or something similar is even a Photon will not read on that scale. This is the problem I am having with the brighter Surefire lamps. Even if I set a Surefire M6 away until I get a reading of 1000 (the highest the meter goes) then I get absolutely nothing even with an E1. I think I will have to set a distance, the 1 foot mark seems to be fine for LED lights, but I am guessing maybe 5 for the incandessant, and 20 for the Surefires.<HR></BLOCKQUOTE>


Hmmm, I see...well...hmmm... how about we all agree to a standard filter setup...I guess I`m thinking something like (don`t laugh to hard, it`s only a quick thought)placing...for example, a layer of toilet paper inbetween brighter lights and the meter. We could say " I got a reading of 50 with a T2 filter" meaning two layers of brand x tissue. We would have to agree on what brand of course. And we would still have to agree on a way to calerbrate our meters to read the same...maybe have Craig measure a lower watt house bulb at a longer distance and set ours to read the same

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>I would like to meter them all by shoting them at a white screen then metering that, but again I get a reading of maybe 3 even with an Eternallight, so most of the lights read nothing that way.

Brock<HR></BLOCKQUOTE>

Ops, sorry I screwed up the quote some how, but you get the idea...if we could find out how many layers it took to get a 1/2 reading...we could mesure higher light values accuaratly...if you have a light that (for example) shows 1000 on the meter (your maximum)...insert tissues to cut that in half to a reading of 500...then using the same filter and a brighter light...say reading 750...you know that it`s putting out 1500...

It would probably be better to use a lower light to find the half way point...say 840...insert layers of tissue till it reads 420... your thoughts please?

Brock... your reading of "1000" and "3", what do they represent in your meter's scale? Lux? What do you think "hardware" or "method" problem?

I'm not not sure what the numbers from site below means, but it seems they already measured brightness and darkness.
http://www.intl-light.com/handbook/ch13.html
Choosing a Radiometer

Billion-to-One Dynamic Range:
Sunny Day 100,000. lux
Office Lights 1000. lux
Full Moon 0.1 lux
Overcast Night 0.0001 lux

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 2d_edge:


Each level will then be sub-rated according to degree of color and intensity of lightbeams, example: A1, A2, A3, B1, B2, C4, D1.

All lightbeams with rings will go to lower level "C" or "D" regardless of whiteness and brightness. Smooth even beam of light gets "A" level rating and anything less gets lower rating.

Hey guys pitch-in what's in your minds.<HR></BLOCKQUOTE>

I think this is an excellent idea...we could adopt this as a way of rating beam quality in addition to simple total light output.

In addition we could rate rings for example:

Brinkman: R7 sharp (6 rings sharply defined)

Arc: R3 soft

Infinity: R2 soft

Expedition: R0 soft confused ...hmmm ???

Some might be a little hard to rate but maybe someone could come up with something (multi LED lights)

My meter is scaled to Footcandles (FC). I don't think there is anything drastically wrong with my meter. The problem is the lights I have vary by more than 2000 FC. The Surefires are just too bright to meter at the 1 foot range, which is where the meter is suppose to be correct.

Brock

Brock-that G.E.# 217 meter does have a switch (for x10) on the side doesn't it?

It has a 3 position switch on the side. The ranges are 0-50 0-250 0-1000 It also came with a metal cover that sits over the sensor with a bunch of holes in it. I haven't played with that much. I wonder it that cuts the light by 10 or something along those lines. Yup just tried it and it is very close to 10 times brighter without the metal cover with the holes. Very intresting...

Brock

Along the lines of a toilet paper filter...
I would like to suggest the use of nd-nuetral density filters or gels which are commonly available at photo supply stores. The nice thing about these, is that one knows precisely the amount of light reduction. As an example, an nd-2 filter allows 1/4 to pass, an nd-3 allows 1/8....
think in terms of f-stops on a camera

Ooh, much better Ted

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mr Ted Bear:
Along the lines of a toilet paper filter...
I would like to suggest the use of nd-nuetral density filters or gels which are commonly available at photo supply stores. The nice thing about these, is that one knows precisely the amount of light reduction. As an example, an nd-2 filter allows 1/4 to pass, an nd-3 allows 1/8....
think in terms of f-stops on a camera<HR></BLOCKQUOTE>

Well, at least using neutral density filters removes us from potential "which brand of tissue" problems.

I'm getting lost among all the topics discussing absolute and comparative light measurements. Two questions,

- could the KenB collector possibly be used to even out the different light meter detector sizes issue ? Especially for luminance levels ? If we have 2 places, Brock's and telephony's, then 2 sets of comparable relative measurements would be a good start.

- at what level of ambient light are the measurements taken ?

There are so many ideas floating now, is someone willing to sum up what seem to be the generally agreed points around this stage, across the topics ? (Just sticking to light outputs only, not the other flashlight considerations like run-time, durability, etc)
I mean, is 20' the distance for assessing incandescents? (Or 6.1008 metres, as Tim would say)
What are the agreed grades for colour and evenness of light ?
How are we going to define the centre spot, is beam half-angle the best way ?

More than 2 questions there, sorry !

Speaking personally, my Sincere appreciation to Everyone who actually has Contributed to providing the Actual Answers in the debates.

Lite-Lover

all technocalities aside, i found that using a simple "on at dusk off at dawn" nite-lite would tell which light was brightest within a few feet in this case. turtlelight 2 would turn it off within 4 feet, ledcorp single led in arc-white about 5 feet and brinkmann about the same, assuming the brightest part of the beam was aimed at the "photocell"?