I think the drop-in is a good idea. I think I am pretty accurate with the lights i have to test but it would be a good comparison. Another reference point. Sphere is looking good X.
JohnnyMac, Langcjl hopefully makes my point a little more clearer. If there's a bunch of us with I.S.'s, it would be nice to have one light or drop-in to use as a reference that we can pass around. As far as a homemade drop-in with so many variables, as long as it's current regulated it won't matter in the slightest. The drop-in lumen rating won't be calculated off of any data sheet, but rather in my I.S. then passed on.
I thought my explanation to Bort was clear on this intent...but hopefully this helped a little more.
Would you have to qualify which light the drop in was used in, such as a single 18650 light, versus a 3AA light, or a 26650 light? Or which exact batteries were used? I hear “regulated”, but I’m still wondering what would happen if a battery that was marginal in amperage or voltage wouldn’t mess up the test?
Ya, but you know me... Have to do it differently. Like making the first layer of newspaper out of "gores", so the inside has very neat seams. Using the weldwood for stiffness and longevity. Using some type of fabric like denim or strong cotton, for more stiffness, etc, etc, etc. LOL, it's got to be a challenge and it's got to be a one of a kind. I just don't know any different.
Almost all the light for white LEDs of any color temp is between 425 and 750 nm. There is a pretty significant peak at 450 nm and virtually nothing below 425 nm.
So when you shine the light inside the sphere, do you shine it straight at the baffle? I'm assuming so given the point of it is to stop light going stright from the torch to the sensor.
No, you shine at the opposite wall. The baffle actually means an imperfection in the sphere geometry and thus is something bad, but direct light from source to detector is much worse.
What about making the first layers out of white paper?
I want such a sphere too and I thought that if we all get our olight i6s(I guess a lot of us have ordered this light) we can calibrate our spheres to each other…
I just found and read through this entire thread. And dangit! Now I’ve got to build one too! Wouldn’t ya know my son just burst a 20” rubber ball and we threw it away?
Figured I’d give this thread a good ol’ necro bump.
Going to try my hand at making one of these spherical beauties in the coming weeks. No idea what I’ll use for the calibration… And I’ll need a light meter!
Funny, I just started at one just yesterday, before you dug this thread out :-) , only 25 cm (10ish inch) diameter because I do not have space for a bigger one, but using the 'match' method. No idea when it is ready, or if it is any good at all, but it has been a loooooong time since I last did paper mache :-)
Barium sulphate,out of date epoxy/polyester resin is quicker and stronger,after an initial papier mache layer,ping pong ball for light baffle,it's round so no direct reflections.Also,I might make a second light meter hole just to check the readings are the same.In theory,an IS puts out an even spread of light everywhere,that's the point!Always good to check.I stuck a layer of plastified foil(ground coffee packet)opposite the light source on the principle that ,for any excaping light through the sphere,throwers will lose more than flooders and hence underread.Opinions welcome
Considering that you can buy a 16” strofoam sphere for $40, I would not waste my time messing with paper mache, etc. The styrofoam spheres that are now available seem to all be made with a flat surface on the ends of the interior. I made a sanding jig by tracing the sphere inner radius onto a 3/4” thick board, cut the board, placed sandpaper over the edge, and sanded the flat spot to match the sphere radius.
Instead of barium sulphate, a light sanding with fine sandpaper on the interior of the styrofoam sphere will remove the sheen and perform pretty much as well as the sulphate/latex paint coating.
Epoxy/polyester can yellow with time. I would not use it.
How much to ship that foam to Canada, plus styrofoam does not reflect all the light striking it, i have styrofoam boxes that i can put a light in and see maybe 10% coming out the other side (maybe 3/4 thick), i would assume the paint will reflect more of the light, now mind you if the light penetration is linear with increasing brightness then a calibration should compensate when taking readings, if i had some calibrated lights of very varying brightness it would be a worthy experiment (unless you already did it and have data to share)
The reflectivity of the styrofoam is not much of an issue… it drops out when you calibrate the sphere.
With my sphere, I can do around 5000 lumens with the sensor mounted in the sphere. With the sensor mounted on the outside wall (using the styrofoam as a light attenuator) I can do over 600,000 lumens. The sphere is absorbing over 99% of the light.
Styrofoam is light… but bulky. Shipping to Canada should not be to bad. You might be able to find a local seller.