Another Integrating Sphere…

Well, made the trip to Wally World and snatched the last 17’’ ball left. I got a few strange looks at the check out counter but no one buying flashlights.

Today, got the first full coat of newspaper using thin coat of watered down wood glue and paint brush. I went slow, trying to avoid any wrinkles, in first layer fwiw.

Anyone that likes to work with music playing, I would suggest Strokin’ by Clarence Carter.

Reading up on calibrating the thing using the sun vs opening size with any suggestions considered. Not sure if ordinary light bulbs could be used as the lumens are printed on the pack and I do not own any light with known lumens. I do have a 501B from Amazon claimed to be around 3000 lumens or so…

No light meter yet but saw a couple listed. I found few threads from BLF so get to read through these while the glue dries. I found the Integrating “P Trap”. Very interesting but wonder if bends may absorb light?


I used many brand-name ANSI rated flashlights with accurate known Lumens & lux to calibrate mine with.

have an old Mag-Lite XL-200. I will have to check if its ANSI rated.


Once you get your luxmeter you could do it like this:

Make a hole with a accurate, known size. Use the lux meter to measure the value at an angle and height, normally on a table or floor where the setup will be stable, where you can put the IS with the hole positioned in that spot with that same angle as when you measured the lux value.

Now you mount the meter and set the box in the spot where you have measured the value with the meter and read the result from the meter.

Since lux is Lumens per square meter you now calculate how many lumens came through the known hole and you have your first value.

Now move the IS away from the light source, or nearer - just move it really, and take another set of readings the same way and do the same calculations.

Now repeat until you think you deserve a cold one.

Just my 0.02 USD

You just this morning stimulated me to continue the characterisation of my own sphere, thanks for that. It certainly appeared to be not as straightforward as taking a flashlight with known output, do a IS reading with that, and there you have the conversion factor for the sphere. But that could have something to do with the small size of my sphere. My problems are certainly related to my ambition to get IS-readings within 1% accurate.

Will update soon..

I read a similar post where the sun was used as the source. If “light in” port a known accurate size then this should be a constant for calibration.

I have to search back but was hoping an incandescent bulb, lumens printed on box, could additionally be used as an LED calibrator? I wonder if the GE printed lumen specs are as bad as some of the LED flashlights;)


as I just noticed I must have hit two days of obituaries of 1” wide newspaper strips! Tomorrow it will be the sports section.

As quoted in many posts, this is slow going, about 1 hour per layer if I don’t drift and try to read damn thing. I noticed on second layer that I would loose track on areas covered for even layers. I now draw crude long and lat lines to know where I missed.

Buy the Styrofoam sphere if you have a life :wink:

so drilled the two holes using 90 degree offset. The strange markings are computations to align with stars to drill first hole. My wife does not believe it either but happy to get card table back.

Interesting, as after first ice pick hole was made only slight amount of air came out. 10 minutes later very scary sounds were coming from inside sphere with dog ready to make confetti out of it. The inside is really smooth, I used water proof wood glue throughout but expensive at $14 total for glue.

Next up is painting then meter set up. I got the Dr.Meter from ebay $30.

Did you remove the ball at some point, or is it still in there? I didn’t see you mention.

I pulled ball 4” out of 4.5” input hole, cut, the rest very easy pull out.