Question to pk. Lumen rating. How is it done?

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

Yes we have two lab spheres.
And we do gives 'real' lumen ratings, including reflector and lens deficiency.<HR></BLOCKQUOTE>

pk..... could you please enlighten me more in layman's language how its done.

Do you pass lightbeam into a device and measure the lightbeam going out of the smaller opening at the other end? That's how I imagine it might be done because light sensors I see are too small to capture lightbeam in its wholeness as it emits from flashlight's bulb, reflector and lens.

Does the lumen rating represent the brightness of the beam in its wholeness or just a part of it... say the hotspot?

I aim to improve my knowledge.

- verge -

Don't know how SF does it, but here's a link to the Ulbricht sphere: http://w4.siemens.de/en2/flash/press/picture_archive/monthly/archive/11.html

Look here also: http://www.optronik.de/plit_en.htm under "Integrating photometer".

Wouldn't it be cool to have one?

P.S. This link shows a sample setup: http://www.eam.admin.ch/en/labors/7/71Source.html and see also: http://www.metas.ch/en/labors/7/73gonio.html

Thanks much JB! That Ulbricht sphere is one very impressive machine.

Yes it's cool to have one.... only I'm not sure I'd know how to operate it and the cost of that machine...... will it fit in my room?

- verge -

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 2d_edge:
Do you pass lightbeam into a device and measure the lightbeam going out of the smaller opening at the other end? That's how I imagine it might be done because light sensors I see are too small to capture lightbeam in its wholeness as it emits from flashlight's bulb, reflector and lens.

Does the lumen rating represent the brightness of the beam in its wholeness or just a part of it... say the hotspot?
<HR></BLOCKQUOTE>

The sphere I used was about 1.20m in diameter. It always depends on what you want to check, they come in different sizes. It will fit in your room.
And the luminous flux in Lumen gives the amount of light coming out of a light source (as perceived by the average human eye). It has nothing to do with a hotspot or if the light makes 'rings' or whatever. And it also is NOT the amount of light energy (in W) coming out of a light source.
You put your light source into the sphere and it 'catches all the emitted light' for measurement.

Additionally, when you got your sphere (and your education, can you imagine me giving my professors a hard time?), you have to add several other devices to your playground: A light colour meter and a 'battery simulator'. I really don't know if such a device exists, but it should not be too difficult to make one.

2d_edge,
May I suggest to following link: http://www.labsphere.com/tech_info/tech_pub.htm
'Hope you find it useful.

pk

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by pk:
May I suggest to following link: http://www.labsphere.com/tech_info/tech_pub.htm
'Hope you find it useful. <HR></BLOCKQUOTE>

Thanks for the link... haven't gone through every topic on it yet, a simple straight answer from you will be appreciated more.

- verge -

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 2d_edge:
... haven't gone through every topic on it yet, a simple straight answer from you will be appreciated more.<HR></BLOCKQUOTE>

You take the sphere, put your light (for a bare bulb) into it or at a specific opening (for a flashlight) and you get the reading (usually several samples are taken and averaged). Of course it is good to have repeatable circumstances .-)

Thank you very much PeLu!!

You have explained to me how that sphere works in words I can easily understand without having me go through the rigors of those techie terms.

We are together on this forum because of common interest in flashlights inspite of various academic training.

Understandably electrical engineers or those with relevant education and training know more or have better technical grasp of the subject.

I hope members with specialised training or higher technical knowledge on the subject of "light" will have the patience to bear seemingly stupid questions (mine ) by members of this forum.

Btw, it's really cool to have that sphere to play with flashlights and learn those technical stuffs. But then is it more fun than going outside and beaming my SureFire 12ZM, LSI RC-3800, or Gadget DB37 (saving to have one) flashlights to watch squirrels or other animals move around in the dark?

- verge -

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 2d_edge:
Understandably electrical engineers or those with relevant education and training know more or have better technical grasp of the subject.
<HR></BLOCKQUOTE>

The problem is also that they have beaten several DONTS into our heads and we have to avoid to do the same with others. And of course, there is a big difference how to face a problem. I would never try to start building a circuit without at least some basic training. But people are different and that's the spice in the soup.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Btw, it's really cool to have that sphere to play with flashlights and learn those technical stuffs. But then is it more fun than going outside and beaming my SureFire 12ZM, LSI RC-3800, or Gadget DB37 (saving to have one) flashlights to watch squirrels or other animals move around in the dark?
<HR></BLOCKQUOTE>

Two different things. I also like to swim around in a lake and I also like my bathtub at home.
Anyway, I think I have one of the better use/play ratios with my lights of the flashaolics around here .-)

(use: when you need a light, play: anything else what you do with it)