Texas_Ace BLF Calibrated Lumen tube / Sphere No math skills needed - Several spheres still available

Oh, a neighbor has joined BLF - welcome.

Thanks for the welcome and hello to everyone! I am new to this forum stuff :slight_smile:

I am currently building one for someone else, the parts should be in tomorrow for it. I am not 100% sure if I will have enough diffusers left to build another 3.5” after that but I think I will have just enough. I will contact you when this one is finished and let you know what I have left.

I just don’t want to oversell before I know for sure I can fulfill the order.

I should have enough for a few 4.5” left worst case since they didn’t sell as well and I have more parts left over for them.

Welcome to BLF Jobane, enjoy your stay!! . :+1: . :slight_smile:

I got his made and after going through all the extra parts I found a few that had minor mistakes from the laser cutter that I didn’t use the first time around but should work just fine if I mix and match them to make them fit.

So I have the parts to build 1 more 3.5”sphere and a few 4.5” spheres.

I also suppose I could cut the 4.5” parts down to 3.5” if desired as well.

Emisar D18 5000k SST-20 with freshly charged Samsung 30Q batteries. 13500 OTF at turn on 10700 at 30 seconds. Large step downs from there 3000 lumens at 3 minutes.

@Texas_Ace

I would like one.

Hello,

Hope it is not too late!
I would like to purchase one 3.5”

I have messaged you.
Thanks.

Thats about right… i got 14040 lumen @ turn on with my d18 sst20 6500k… i find sony vct5a solder blop make about 1000 more lumen than 30q.

I really need to get on this list for the 4.5” version, How can I
do that?

Howdy, The ground buy / list is over, I am now just making them 1 at a time from spare parts by ordering the missing parts as needed. Now to get one you just need to send me a message.

I am sending you a PM and we can sort it out there.

TA, sorry to bother, but since i am trying to build one myself, i am interested in the most important things which i have to take in mind to get a reliable setup.

I am using three white 90 degree pvc bends , use a glass lens inside the tube to have always the same distance to the luxmeter and i am using a frosted pvc piece inside the tube as a diffuser.

What other factors do i have to take in mind?
What about linearity ?
How to optimize the lumen tube to get a good setup?

Thank you in advance

The diffusors are the mot important part. Using the right kind and multiple layers is the best option for balancing out different beam profiles.

Using glass as the first layer is ok, but I find it to be a better result when you capture all the light with the reflective centering rings. This stops the light that is reflected back out of the tube from skewing the results too much. This makes it more like a classic lumen sphere then a classic lumen tube.

Basically a hybrid lumen sphere/tube.

Past that it is trial and error to get everything figured out with the specific materials and setup you are using. Luckily Now that I have built several of them I have most of the details figured out but there is still quite abit of individual testing and calibration for each tube. No 2 seem to be exactly the same for some reason so I gave up and accepted I would have to build them all individually.

Sucks since I could cut the time per sphere drastically if I could just slap them all together the same way and they would have the same results.

Thank you TA, i will try that.

Strange indeed thet every tube gives different results even when you built them all exactly identical, probably small deviations in production of materials, hardening of material when they come out of the mold, or something like that.

Yeah, the materials can be different for sure. Another factor is that every mm difference in how far they are pressed into each other has a surprisingly big effect on the final readings. Since it is basically impossible to full bottom them all out this varies tube to tube enough that the readings have to be individually calibrated for each tube.

Another question, i noticed when using high output lights, the white walls do light up slightly, do i need to paint the outside black?

No, light escaping into your room or being absorbed by black paint is the same thing, in both cases it leaves the tube.

Btw, integrating/measuring total light output is not about getting as many photons to the detector as possible, it is about any photon emitted by the light source at any direction having the exact same chance to reach the detector, but that chance by no means needs to be high.

Thanks for that info!

Still struggling to find the correct conversion factor, i just found out i have to many lights that are modded or lights i dont know the exact lumen output of, besides the fact that the output drops quite fast even on fresh charged cells.

Is there a good and cheap method to have a calibrated light ?

Does this reflect light across the wavelength evenly enough?

What is enough? My integrating spheres show a resulting spectrum with reduced blue (about 600K CCT-shift if I remember well) after multiple reflections, and every diffuser in the light path causes extra blue loss too. This tube has both multiple reflections along the way and two diffusers so I expect a rather large effect on the spectrum. But the main affected region is the blue region which contributes relatively little to the lux-measurement. Moreover, the cheap luxmeter used in this device over-reads blue so a bit compensation may not be bad :wink: .

But to answer this question thoroughly, one needs spectral measurements on the device which has not been done, to see the amount of spectrum-change, and the amount of accuracy-loss when light sources of a wide range of CCT’s and CRI are tested. If it is really bad, a different multiplier per CCT-region could be used to compensate for that.