No worries, thanks for your remarks. You have lots more experience in this type of thing
From what I’ve read, I could not get a conclusive answer if I should do it or not? I’ll take your advice. Will report back as soon as its done. I’m curious to see how its going to affect the figures.
I’m not worried about this. Its white carton and the way I’ve attached it will prevent this from happening. I’ve cut a ‘supporting pillar / foot’ on each side of the baffle base, each bent 90 degrees in opposite directions. The center part of the baffle base slides into a groove that has been cut into the styrofoam. All glued with styrofoam-safe glue. The baffle will not shift / move / change orientation.
I would have liked to build a much bigger sphere where this effect would have probably been minimized. To try and find a multiplier for each plate / hole size is obviously not easy. For now, and whats practical to build / implement by me, I’ll just accept the, possible small, percentage of inaccuracy.
With the sensor mounted inside my sphere, I can go to around 5000 lumens. With the sensor mounted to the outside of the sphere (using the sphere wall as a filter) I can go to around 500,000 lumens.
I currently have the same issue… my limit is around 5100 lumens. I’m thinking of maybe just fitting some kind of a filter (piece of film) over the light meter hole inside the sphere? What do you think, will this work? Its going to be more difficult for me to shift the meter further outwards. Don’t want to tamper with the mounting mechanism now.
Indeed very nice build. Two questions:
How did you get multiplier estimate? The lumen numbers sounds high to me.
For the the C8 test, you got >1600 lm. Is this possible? (Cree spec for XP-L V5 at 3A is 1058 lm. V6 maybe higher but not by that much.) What is the tail current?
I’ve estimated my factor by measuring a handful of standard ‘name brand’ lights. Its basically all the ‘Stock’ lights in the list above & 1 or 2 additional ones thats not listed…
I don’t have the C8 mentioned above anymore, so cannot measure the tail amps. I’ve measured another C8 XP-L Hi V3 2B now and got 1625 lumens with turn-on and 1555 at 30s. Tail amps were measured at 5.0 amps after 30s with my fluke 374 clamp meter.
I don’t know about official tests here on the XP-L Hi V3, but Djozz did some testing on the XP-L Hi U5 - around 1600 lumens. According to he’s test, I believe my figures above might be in line. I’m definitely not saying Djozz’s figures are 100% accurate, this is the only figures I can bench against here.
But, I still have a good feeling about my figures measured above, and my current sphere multiplier. I believe its accurate to around 10% up or down. I can live with that.
You’ll see that some of my stock light measurements are below the advertised lumens, e.g. Maxtoch 2X. Its rated at 1300 lumens, I measured 1215. Same with the Thrunite T10. Its rated at 169 lumens, I measured 147. So, I did not just pick the highest multiplier possible, I did try to find a happy medium between my stock light measurements.
I should probably sign up for the light currently travelling the world to get our spheres in comparable state :).
O.K. May be you are correct. I don’t have many of these flashlights anyway so I probably shouldn’t make the judgement.
For C8, if your current is 5A, 1600 lm could be possible but I don’t have a driver can produce that high current anyway. BTW, what driver do you use to generate such a high current?
For the Convoy s2+ 18350. Is it one 18350 one? Again can you find out what is the tail current it took for the measurement if you still have it?
I am trying to get my IS calibrated so I would like to have any information I can have. Thanks.
Not sure what the question is here? This is the S2+ ‘Short’ running an Efest Purple 18350 battery.
I’ve realized an error in my OP list. The Convoy S2+ 18350 does not run a dedomed XP-L V6 but rather a dedomed XM-L2 U4 1C. Sorry about this. The tail amps measures at 3.5 amps after 30s.
Yes, it should work. You want your filter to be neutral density and not cause any color/tint filtering/shifts. Avoid white paper with UV brighteners in it. Maybe find some stoner kid/hippie and borrow a few cigarette papers. I measured some and they seem to make decent filters.
At least a filter should look white or grey when you shine white light through it. A significant tint shift can simply be seen as a colour. And subtle deviations from true white or grey will also not give a that worrisome tint shift (I think).
In my first sphere I used a piece of greyed black&white film as a filter. But I like the idea of a piece of cigarette paper :-)
(as for a coating of the inside of the sphere, that is a different story, light is reflected multiple times before reaching the sensor, any slight tint shift caused by the coating will be multiplied as well)
Slick may I ask where did you find the large hollow Styrofoam ball and how did you settle on the dimensions? I have been wanting to build one I just have no idea where to start,I think you did a great job!
Thanks Djozz. I’ll see if the arts shop has something more interesting… will report back, hopefully with some photos of a few options. PS: I’ll include the cigarette paper as an option.
Thanks… I was lucky to find the ball at the same arts & crafts shop mentioned earlier in this thread. Earlier this year they actually had bigger balls than the one I’ve used. I had my eye on 1 of the biggest balls, did not take measurements then. When I eventually got to the point to go an buy the ball, the bigger ones were sold out - I was so disappointed. To make things worse, the shop did not plan to get in new stock soon. So, I just had to settle for the smaller size ball. Till date, I could not find any other suppliers of these hollow balls. I’m situated in South Africa.
My sphere controller has a color sensor mounted to it and I can calculate the CCT of the LED. I use the green channel of the color sensor for lumen readings. I calculate the CCT using several different algorithms… the simplest one uses the ratio of the red and blue channels. It agrees quite well with the rather complicated formula from the sensor maker (Taos) that uses all three channels.
The papers that I tested did not significantly shift the color temperature, only the intensity.
And you don't even have to go to shady shops to get them, even without 'wiet' in them, the dutch are the no1 rolling tobacco consumers in the world :-)
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