How to make a "lightbox" ?

Hi guys!

I ordered a Digital Lux Meter from DX for my future measurements. It has arrived today to my post office and now would be a good

time to build a "lightbox" as mentioned here (BLF) in many occasions. It seems that a simple cardboard box would be a good start ?

I would like to see your solutions for it (pictures)

Don, i know that you have one. Could you make "a mini review" for it ?

I use a ATX Power supply box [ Computer power supply ] ..

I cut a slot at the bottom [ middle ] and cut a hole , on the opposite side , top .

The light meter is a very tight fit [ keep out light ] as you want 0 reading ...

I take a minimum reading as its more accurate than say a maximum reading ... [ flashlight ]

You just need to do what ever you do the same time every time .. [ set your own procedures ]

edit: I posted my lazy solution. It probably isn't that great. You should probably find something unique and not just something I thought up in a minute.

Finished my lightbox:

Its not pretty but it will do the job. Now i'm ready to make my first review.

Its made from cardboard box. Inner and outside are covered with aluminium foil and paper. Its pretty "light tight".

My box look rather like yours. I used a bit of translucent plastic cut from a milk container to act as a diffuser and to prevent dirt from getting in the top hole.

I put in a barrier in the middle so that no light can go directly from the torch to the meter, it has to bounce around a bit first. Think of it like the letter "T". this hangs from the top of the box.My meter's sensor is held in place with the extremely high tech approach of duct tape. I have put cardboard flaps over the input and meter ports to keep light and dirt out.

aluminium foil

Usually an integrating sphere is covered on the inside w/ diffuse material, or the exact opposite of reflective.

Yes, that's why i use paper to cover the foil. The box isn't reflective inside.

The foil is for make to box "light tight" so that outside light sources won't interfere.

All you need to do is work out the light output on several of your lights : [ Driver efficiency ] vF cF , type of emitter , and your good to go after some math ...

That's a pretty good idea, but be sure to crinkle it up first to reduce directionality.

If you have a laser, you can use it to test the effectiveness of your contraption as well as troubleshoot consistency. Readings shouldn't change with it pointed to different angles at the input.

I like the way you explain it. ROFL

I made a quick run trough for my lights.
Here are the results:

Brand and Model Battery type Switch on LUX
Mrlite KC-05 1xAAA 208
Ultrafire C3 1x1450 803
Ultrafire C3 SS 1x1450 535
AKOray K-106 1x1450 610
Fenix LD10 R4 1xNiMH 534
X2000 1x18650 750
Trustfire SSC P7 C-BIN 1x18650 1240
Ultrafire WF-502B MC-E 1x18650 1614
UltraFire WF-1300L 3x18650 5005

There are few suprises in the results:

- Ultrafire C3 with black anodising is brighter than its stainless steel version

- Trustfire P7 seems to be somehow broken becouse my new WF-502B MC-E beats it easily.

The reading is from first second at the start and it starts to drop significantly. After 10 sec its only about 900 lux.

- I always thought that WF-1300L is bright and it truly is, up to 3x brighter than WF-502B MC-E

The Romisen MXDL-RC-G2 is missing because its in my car and i'm lazy today...

I'll do a better version of the table with more information about brightness in different runtimes.

With my lux meter on the way... im going to make one of these.

Since i would love to have cosistent readings what's the best way to design the "integrating sphere"?

The sensor of the light meter should not allow other light to go inside. (poorly made hole).

The internals should be made of non reflective material. What would be best? Lined with a old cotton shirt?

The aperture for the flashlight should probably have the antique photo camera rug installed so no other light can pollute the internals?

Shape? Sphere seems logical, but is really that disruptive going for a square box? A dodecahedron would be batter than a box?

A cheap plastic ball might be just the thing. Cut in half, and then heavily brushed to kill any reflectivity. Glued together and glued/ in a wood cage to preserve shape...

If i understood correctly i win if i get my measurements cosistent, but i will never be able to know if my calculeted lumen output of 320 in reality can be 304 or 330?

Any suggestions?

It is important that no light can go directly from the torch to the meter's sensor, it has to bounce around first.

Thanks for the good reading. :)

Being lazy and hating the maths led me to set mine lightbox to direct reading in Lumen.

Calibrate it with the ITP A3 the only 'trusted' stock not touched I own as 85 lumen in high 23 in med...given the readings I get probably the actual output in mine is 80...

RC-G2 with XR-E R2 at 1,4 A 340 Lumen

RC-G2 with XP-G R4 at 1,4 A 408 lumen

RC-G2 stock XR-E with rechargable cell 130 Lumen

MTE F15 P7D at 2,4A 620 Lumen

P10 with XP-G R5 at 1,4 A 470 lumen

I think all the number are too high maybe 10% or a bit less

I need to work in the reflection issue because the throwers perform way better than the flooders or candle mode...