WTS: Calibration lights for DIY integrating spheres / lumen tubes - 67 € -

2020 October: No kits available at the moment

Update 22.1.2020: Current calibration set consists of two Convoy S2+ with XM-L2 (low CRI, cool white) and SST20 (high CRI, neutral white). Price for the kit is the same at 67 € including two lights.

Update 14.3.2019: Interest list for a throwier calibration light (Convoy C8+) added. Only 1 piece measured and ready to go now.

Update 20.12.2018: Interest list for an ultra high CRI Nichia Optisolis modded Jetbeam added

After some interest from people wanting to calibrate their integrating spheres / lumen tubes I decided to make these little calibration kits available. For 67 euros you get two lights shipped anywhere in the world and you won’t have to rely on manufacturer or reviewer ratings, which might vary as much as 20% between samples even in the same batch. Read on for details.

As of 20.7.2018 I have ordered enough lights for 40 sets out of which about 20 has been tested and shipped. More will be made available as long as there’s interest and I am able to find reasonably priced suitable lights

The lights

For the calibration kit I’ve chosen the BLF348 and Convoy S2+ as they have a very consistent output (S2+ on low and mid). In my testing the output of the BLF348 stays within +/-1% regardless of the NiMH battery used between several measurement rounds. I still recommend using a fresh Eneloop or Ikea Ladda as a worn battery with high internal resistance will not work reliably. For the 7135 regulated Convoy, it doesn’t really matter which 18650 is used and the repeatability makes them perfect for calibration.

The lights have also been chosen to have different color temperature and CRI. While the BLF348 is neutral white (4500-5200 K) and very high CRI (Ra >90, R9 >80) the S2+ utilizes a cool white XM-L2 (~6500 K) with a low CRI of about 70.

This should give you two good data points to check whether your lux meter is affected by the differences in the spectrum. If the difference is large, you might want to use a different correction factor depending on the light being measured.

Total price for the kit with two calibration lights and data is 67 euros.
(PayPal will handle the conversion for you if you’re not in the EU)

First shipments should be ready to go out the door within two weeks while I wait for some S2+s to arrive.

Payment is done via Paypal (goods and services) or the equivalent amount of crypto (BTC, LTC, ETH, BAT…).

The price includes shipping anywhere in the world. I will send the lights without their original packaging padded in an envelope. This is due to the 3 cm limit for envelopes. Shipping time will be approximately 1-2 weeks to most countries. Up to 4 weeks to the remotest areas such as New Zealand.

There will be no tracking

If you need tracking the cost will be 87-100 euros depending on the country due to the high price of shipping packages from Finland.

For disclosure, the total price consists of 30 euros for the measurements and generating the data. Everything else is to cover the cost of buying the lights, shipping, packaging and paypal fees.

If you are in the EU, you can also send me your own lights to be measured. The cost of lumen measurement is 20 euros for the first light and 10 euros for any additional ones. You pay for shipping both ways. Remember that shipping boxes out of Finland is very expensive, especially if they have to be tracked.

In this case you can also request which battery should be used for testing. Do not send me any batteries. I have a wide range of 18650s.

While I already have procured some BLF348s, I’m still waiting on the Convoys. Let me know if you are interested and I’ll order more as needed.

What you get

The measurement report contains luminous flux in lumens at 0, 30 and 60 seconds as well as various measurements from the hotspot such as intensity in candelas, color temperature, tint and spectral data in image and text format.

The equipment used for calibration

The calibration lights have been measured in a 50 cm Lisun Group integrating sphere using an X-rite i1Pro spectrophotometer. The sphere was calibrated using Lisun’s SLS-10W standard light source. This is the setup I use in my reviews.

Sphere album: https://imgur.com/a/EbqM3

About spheres

The problem with calibrating an integrating sphere based on a flashlight that you have and some reviewer has tested is the big differences in LED bins and driver component tolerances. After measuring 10 BLF348’s from the same batch, I found output differences as large as 15%. Same goes for a seemingly reputable manufacturer’s specifications.

The point of a calibration light is that you measure the lux from your sphere using a light with a known output and then divide the given lumen output with the lux value. This gives you the correction factor which is used when measuring other lights.

For example, you get a calibration light which outputs 34 lumens. You measure its output in your sphere and the meter reads 100 lux. This means your correction factor is 34/100=0.34 which is used to multiply any subsequent lux readings to convert into lumens. A light that reads 500 lux is 500*0.34=170 lumens.

For information on how to make a DIY integrating spheres check out threads by djozz and JoshK. The widely used lumen tube uses PVC plumbing pipe, the latest thread on the subject is by Texas_Ace, which was also later calibrated by lights I tested for TA.

Please note, that the biggest problem with these devices arise from lights that are especially floody or throwy. If your lumen contraption is not integrating the light well enough, the numbers will be too high when measuring throwy lights. This is why it’s very important to try and diffuse the light as much as possible before it exits the sphere/tube and hits the meter. Matte surfaces, baffles and diffusers are your friends.

Interest list:

1st batch (estimated shipping: 20.7.)

  1. emarkd shipped
  2. yasenf shipped
  3. Bob_McBob shipped
  4. moderator007 shipped
  5. SKV89 shipped
  6. teacher shipped
  7. shirnask shipped
  8. Terry Oregon shipped
  9. peabody shipped
  10. Billy X shipped

2nd batch (estimated shipping: 29.7.)
11. Fady shipped
12. nkresho shipped
13. Micael shipped
14. iosala shipped
15. jmm244 shipped
16. vestureofblood shipped
17. KawiBoy1428 shipped
18. ImA4Wheelr shipped
19. JasonWW (S2+ only) shipped

3rd batch (estimated shipping: 6.8.)
20. Muto shipped
21. dmsoule shipped
22. slimkango shipped
23. Pezo shipped
24. fsvendsen shipped
25. Glow_Worm shipped
26. miswas shipped
27. toobadorz shipped
28. Mark M shipped
29. Hoop shipped
30. run4jc shipped

4th batch (estimated shipping: 17.8.)
31. Newlumen shipped
32. leroycp shipped
33. jdavis shipped
34. kasperrr shipped

5th batch (esimated shipping: 1.9.)
35. Funtastic shipped
36. Clemence shipped
37. Kame Sennin shipped
38. DB Custom shipped
39. ktown shipped
40. MRsDNF shipped

6th batch (4 sets ready to go immediately)
41. Talpa shipped
42. rcwiily shipped
43. dsb171963 shipped
44. 808Hi shipped

7th batch (estimated shipping: 11.2.2019)
45. coherent-rambling shipped
46. MtnDon shipped
47. ToyKeeper shipped
48. ZozzV6 shipped

Interest list for Optisolis/E21A powered Jetbeams from Clemence with calibration data.

1. SKV89 shipped
2. contactcr shipped
3. clemence shipped

Clemence thread & at virence.com Jetusolis, JetuE21A

Disclaimer: I’m not sure these will make for a better calibration if you mostly want to test low CRI lights with lux meters, but the smooth spectrum of the Optisolis would be a great reference for future.

Just like with the S2+ and BLF348 or any other light, price for measurement is 15 euros per light plus intl shipping (4.70 or 7.50 euros depending on weight). Does not include the price of the light itself.

Interest list for Convoy C8+ 219C 4000K CRI90: a throwier option for calibration

Price: 50 € if you previously bought a set, 55 € for a new buyer (higher shipping costs due to larger size)

1. Terry Oregon shipped
2. likevvii shipped

Latest batch 2019
54. trailhunter shipped
55. likevvii shipped
56. hcanning shipped
57. ver_ivanz007 shipped
58. BabyDoc shipped

BLF348 and S2+ with SST20 4000K (ready to go)
59. M4D M4X shipped
60. oweban shipped
61. CNCman shipped

Convoy M1
62. contactr shipped


First batch for the new year has arrived and is ready to go as of 22.1.2020. These will be 2x Convoy S2+. Low CRI cool white XM-L2 and 4000K high CRI SST20. This is to verify that the lux meter used reports properly with different spectra.

If you need a thrower for integration testing PM me. Shipping them internationally is more expensive.

63. tristech shipped
64. YogibearAl shipped
65. Watermanchris shipped
66. TexasToasted shipped
67. Elcam shipped

68. ChibiM shipped
69. ChibiM shipped
70. Valor shipped
71. Blenman37 shipped
72. TimMc shipped

Very cool offering maukka, for an extremely reasonable price! That should further reduce measurement errors among the BLF community.

Great, thank you for doing that. :slight_smile:
I’m not yet into building my sphere, but availability of calibrated lights is superb for the community.

Out of curiosity, you provide quite a few properties of those lights. Is everything except for flux measured at 0 seconds?

On the bottom of the measurement sheet it says:
“Intensity, CCT and CRI values measured at 30 seconds”

Should probably make it bigger :wink:


Missed that because it was on a picture.
Thanks for clarification.

Added you to the list and will PM you when your kit is ready to be shipped. No need to pay anything just yet.

Bump. With all the drama around here lately about calibrating lumen tubes I can’t believe there’s not more interest in this offering. Lots of us have measuring devices - group-buy sphere or tubes, homemade boxes, whatever - and want them to all yield comparable measurements so we can have more meaningful discussions. This is the best way to accomplish that goal, and offered for a very fair price.

Really happy to see this idea coming to fruition so quickly. I’m definitely interested in a kit. I agree with emarkd, this should have way more interest given all the recent output measuring drama!

So 64 euros is $71.62 US dollars right? That’s what a online calculator came up with. Well I used another one and came up with $75.18 US.
Could you clarify what the price would be in US dollars please. I’m pretty sure I’m in for the set just don’t know what the Paypal payment should be.

It’s $75.17 USD right now. You’ll probably pay around 2.5% on top of that for the currency conversion from either your card or PayPal. The PayPal payment will no doubt be in EUR so there is nothing to work out.

Just choose sending euros in Paypal and they will do the conversion (with their conversion fees like Bob_McBob said). If you want to pay in USD it’s $78.

I will take cryptos (BTC, ETH, LTC, MIOTA, VET) as well.

Alright sounds good to me, if pp does the conversion. I’m in for the set, just PM when their available. :+1:

Very nice, these as the same lights I used to calibrate my own sphere. I just wish I had had them a few years ago, it would of made my life SO much easier. Well worth every penny.

Plus there is a lot of time involved with taking all of those measurements for each light.

Thanks for doing this. Please put me down. I’m glad the BLF348 has a duv of –0.0025, which means it’s the old batch and not the current batch I just bought with slight greenish tint. Instead of just giving us the 30s lumens. Can you also give us the startup lumens for these?

I am in maukka, thank you. :slight_smile:


Count me in.