Homemade lightbox

[Egsise]

I read about the milk carton lightbox and decided to build something similar.
I know that lightbox readings vary quite much, so I tried to use "standard" size box etc. to make everything simple.

My lightbox is made of carton box that contained 2x500 80g A4 paper sheets.
The flashlight hole is the size of a CD disc, and i covered the flashlight hole with one of those clear CD dummy discs found in cd spindle.



The luxmeter is the DX cheapo.
There is a cooling fan for the flashlight, of course.
Webcam taking shots from the luxmeter, I use Time lapse photobooth v 0.1 for that.

Any ideas how to improve the design?
Any ideas how to make logging easier, now I have to type everything to a spreadsheet, so I take webcam shots only every 60 seconds.(first reading is after 30sec)

 

[Kilovolt]

Nice setup. :thumbsup:


The purpose of the box is of course to collect all the light emitted by the source. In this respect the inner surface must reflect as much light as possible: have you painted the inner walls in white and/or covered them with white paper?

 

[Egsise]

Yes i covered the inside first with tin foil and after that with white paper.

 

[csshih]

Any ideas how to make logging easier, now I have to type everything to a spreadsheet, so I take webcam shots only every 60 seconds.(first reading is after 30sec)

eek!! what if you have a light run for 3 hours?!
that's allot of stuff you have to enter in manually :green:

 

[Tom_123]

Very nicely made.

But as you asked for improvements:

I'm not too happy with this clear disk.
IMHO this will lead to inaccuracy because of reflections and the like.
I'd leave it out.
Here's a pic of my attachment of the lights in my lightbox and my IS.

http://i671.photobucket.com/albums/vv76/_Thomas/Forum Fotos/Lightbox_1.jpg

For some food for thought, there are also some more pics of my equipment in this album:
(Not that I would think this is a perfect solution, but it works quiet well for me)

http://s671.photobucket.com/albums/vv76/_Thomas/Forum Fotos/


As for the measurement, there are mainly two solutions,
but they both comes with some cost:

1. A DMM with data logging ability and a homemade sensor.
(e.g. with an Osram BPW21 photodiode and a low-pass filter)

2. A luxmeter with data logging ability.
The best-priced meter could find so far is the EXTECH HD 400.
(about 150 Euro, here where I live)

http://www.extech.com/instruments/product.asp?catid=10&prodid=56

hope that helps somehow

 

[Egsise]

eek!! what if you have a light run for 3 hours?!
that's allot of stuff you have to enter in manually :green:

Neutral white Quark AA moon mode runtime was 315 hours....:laughing:

Very nicely made.

But as you asked for improvements:

I'm not too happy with this clear disk.
IMHO this will lead to inaccuracy because of reflections and the like.
I'd leave it out.
Here's a pic of my attachment of the lights in my lightbox and my IS.

http://i671.photobucket.com/albums/vv76/_Thomas/Forum Fotos/Lightbox_1.jpg

For some food for thought, there are also some more pics of my equipment in this album:
(Not that I would think this is a perfect solution, but it works quiet well for me)

http://s671.photobucket.com/albums/vv76/_Thomas/Forum Fotos/


As for the measurement, there are mainly two solutions,
but they both comes with some cost:

1. A DMM with data logging ability and a homemade sensor.
(e.g. with an Osram BPW21 photodiode and a low-pass filter)

2. A luxmeter with data logging ability.
The best-priced meter could find so far is the EXTECH HD 400.
(about 150 Euro, here where I live)

http://www.extech.com/instruments/product.asp?catid=10&prodid=56

hope that helps somehow

Thanks for the tips.

I added the clear disk because i noticed that the readings changed if the flashlight was not centered, perfectly aligned, or it was too deep in the lightbox.
Now my readings are always the same, well at least if the flashlight regulation is good. LD10 and Quark AA on medium are very stable...

My setup is far from good, mainly because it was made from the cheapest parts that i could find...
Like 28$ for the luxmeter, everything else was found from my house so this really is a low budget lightbox.

Wait, what, is that a real IS?

Anyway nice setup you have.
Have you tried to calculate the real lumens based on MrGmans measurements etc?

 

[Tom_123]

I added the clear disk because i noticed that the readings changed if the flashlight was not centered,…

Well, normally the readings should not change more than 10%-15%
when you move the light for about 20 degrees in all directions.
If you get more inaccuracy, you may want to install a baffle,
to prevent the sensor being hit by direct light form the source?

Wait, what, is that a real IS?

What is real?
This is a 15 Euro homemade IS , I don't have a lab to provide
even conditions for the measurements, I mostly have only one sample
of each light, my lux meter is pretty inaccurate, and I have no opportunity
to calibrate the setup.
Further, I can't provide a surface for my IS with a smooth and even
+95% reflection over the whole light color spectrum.
Nevertheless, it works quite well for making runtime charts and
compare the overall brightness of my lights.

Anyway nice setup you have.
Have you tried to calculate the real lumens based on MrGmans measurements etc?

Thank you, but there is still a lot of room for improvements.

As for the real lumens, yes and no.
Yes, of course I estimate the overall output of my lights for myself
and the work of MrGman is a real great help here because I don't have any other
way to calibrate my setup.

No, because of the said inaccuracy of my setup I wouldn't make any public
statements about absolute numbers, like "light A has 230 lumens out of the front".
Nevertheless, I can state if my sample of light A is brighter than my sample of light B.
And that's not all that bad for a start.

regards
Thomas

 

[Egsise]

Well, normally the readings should not change more than 10%-15%
when you move the light for about 20 degrees in all directions.
If you get more inaccuracy, you may want to install a baffle,
to prevent the sensor being hit by direct light form the source?

Well with the disc I cannot screw the setup even if I wanted to...
It is almost impossible to get direct light to the sensor with the disc.