Integrating sphere #3 (portable and overly stuffed with features)

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djozz
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Put your styrofoam ball in a cardboard box with a hole and off you go Smile

Sometimes the most scientific method is not the most practical one, in this case for most people the accuracy is totally dependent on the least accurate measuring device on the planet:the dubiously calibrated chinese luxmeter. But if your luxmeter has a trusty calibration the method is really useful.

sixty545
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btw djozz, did you eventually get your CCT measuring device ( I guess you went after a i1Display Pro). And if so, I would like to know the price and the vendor, please. Thumbs Up

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sixty545 wrote:
btw djozz, did you eventually get your CCT measuring device ( I guess you went after a i1Display Pro). And if so, I would like to know the price and the vendor, please. Thumbs Up

Perhaps I should have bought an i1Display Pro..

Instead I have bougnt a very simple device, a homebrand product from Lumitronics named ColorSense. I hoped that it would work straight out of the box, but while playing with it, the reading went all over the place, could not get a grip on it. So I gave up on it for the moment. A thing to try is placing a white diffusor in front of the sensor, like luxmeters have. So I will have to make a little project of it.

http://www.leds.de/LED-Zubehoer/Steuerungstechnik/ColorSense.html

vestureofblood
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sixty545 wrote:
‘obscure’ ?? (my finger hovering over the ‘RUDE’ button Wink ) I would rather call my method ‘scientific’. It uses one fundamental formula: LUMENS = LUX x AREA[m2] and is valid for a uniform bunch of light.

I’m with ya. I’ve got nothin’ but love for your project sixty Blushing I wasn’t meaning to imply that what you were doing was unscientific. I just got a little freaked out when I saw that post by match and then yours. I was like, “have I really been doing wrong for all these years??”

I made a video log on my build of one of the lumen tubes and on my old measuring setup last week. http://budgetlightforum.com/node/47408
I thought it might interest some people who want to build a cheap easy setup who are not as concerned with the level of precision discussed here. However I did want to make sure I wasn’t just spreading grotesque misinformation before posting, hence my badgering in this thread. Any misinformation in this vid will be mildly odorous at worst Grad

In Him (Jesus Christ) was life; and the life was the light of men. And the light shineth in darkness; and the darkness comprehended it not.
http://asflashlights.com/ Everyday Carry Flashlights, plus Upgrades for Maglite.

sixty545
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@vestureofblood:
No offence taken! I did’nt really consider using the new button Wink
Great video of yours btw!
(fyi footcandles and lux are related by a factor just as inches/centimeters).

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djozz wrote:
sixty545 wrote:
did you eventually get your CCT measuring device …

Perhaps I should have bought an i1Display Pro..
Instead I have bougnt a very simple device, … the reading went all over the place, could not get a grip on it.

That’s what I found too, using a PublicLab spectrometer to try to measure color temperature and CRI. I could probably get it to a usable state with some effort and experimentation, but so far it hasn’t been very useful at all.

It’s at least good enough to confirm that color LEDs are the color they’re supposed to be, but that’s easy enough just by looking. For example:

Texlite
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djozz wrote:
sixty545 wrote:
btw djozz, did you eventually get your CCT measuring device ( I guess you went after a i1Display Pro). And if so, I would like to know the price and the vendor, please. Thumbs Up

Perhaps I should have bought an i1Display Pro..

Instead I have bougnt a very simple device, a homebrand product from Lumitronics named ColorSense. I hoped that it would work straight out of the box, but while playing with it, the reading went all over the place, could not get a grip on it. So I gave up on it for the moment. A thing to try is placing a white diffusor in front of the sensor, like luxmeters have. So I will have to make a little project of it.

http://www.leds.de/LED-Zubehoer/Steuerungstechnik/ColorSense.html

Mind having a look at this at tell me what you think? Open Source DIY Spectrometer $45

If I stick with this “Hobby” for a longer stint than last time, I’ve considered buying this…Lighting Passport Smart Spectrometer. I’ve seen them listed for as little as $1295, a bargain for all they do. Measures CCT CRI CQS Illuminance Foot Candle CIE 1931 CIE 1976 Spectrum Diagram C78.377-2008 IEC-SDCM λp. The bluetooth connection is pretty sweet, and I think they would work well in our DIY integrating spheres.

-Michael

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ToyKeeper wrote:
djozz wrote:
sixty545 wrote:
did you eventually get your CCT measuring device …

Perhaps I should have bought an i1Display Pro..
Instead I have bougnt a very simple device, … the reading went all over the place, could not get a grip on it.

That’s what I found too, using a PublicLab spectrometer to try to measure color temperature and CRI. I could probably get it to a usable state with some effort and experimentation, but so far it hasn’t been very useful at all.

It’s at least good enough to confirm that color LEDs are the color they’re supposed to be, but that’s easy enough just by looking. For example:

Should have read further before I hit reply to djozz’s post, sorry TK.

I referenced that same spectrometer above, what’s your opinion of it after using it?

-Michael

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I think it has potential, but getting it to work well is nowhere near as simple as the site would suggest. When I’ve tried to measure flashlights with it, the readings go all over the place, making dramatic changes in response to very small changes in angle or positioning. The software for it is also pretty limited, so if you want to actually do CRI or CCT measurements you’ll probably have to write the tools yourself.

So far it’s kind of a neat toy, but not really a useful tool unless you put a lot of effort into it.

I hope the software has gotten better, but I haven’t looked in at least a year. They have released a new version of the hardware kit, at least, which looks like it might work a bit better, and provided better instructions on building it.

sixty545
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djozz wrote:
sixty545 wrote:
btw djozz, did you eventually get your CCT measuring device ( I guess you went after a i1Display Pro). And if so, I would like to know the price and the vendor, please. Thumbs Up

Perhaps I should have bought an i1Display Pro..

Instead I have bougnt a very simple device, a homebrand product from Lumitronics named ColorSense. I hoped that it would work straight out of the box, but while playing with it, the reading went all over the place, could not get a grip on it. So I gave up on it for the moment. A thing to try is placing a white diffusor in front of the sensor, like luxmeters have. So I will have to make a little project of it.

http://www.leds.de/LED-Zubehoer/Steuerungstechnik/ColorSense.html

Sorry to hear that!
The instrument I made during my time at Philips also had problems with repeatability. The team that made the separate measuring head (with suction cup) started with placing the three sensors at an angle so that they pointed at the same pixels on the CRT screen to measure but they soon found out that a rotation of the head gave a different result. Eventually they ended up using a piece of milky, acrylic plastic in front of the sensors, just as you have in mind. The calibration took care of the slight miscoloring from the plastic. I hope that a piece of plastic will solve it for you.

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sixty545 wrote:
I hope that a piece of plastic will solve it for you.

I should probably try that too. Smile

I had been thinking of trying to attach a really white piece of paper or something at a 45 degree angle and bounce light in, but it’d be physically a lot easier to just stick a translucent sheet of something on the front of the measurement device.

Texlite
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ToyKeeper wrote:
I think it has potential, but getting it to work well is nowhere near as simple as the site would suggest. When I’ve tried to measure flashlights with it, the readings go all over the place, making dramatic changes in response to very small changes in angle or positioning. The software for it is also pretty limited, so if you want to actually do CRI or CCT measurements you’ll probably have to write the tools yourself.

So far it’s kind of a neat toy, but not really a useful tool unless you put a lot of effort into it.

I hope the software has gotten better, but I haven’t looked in at least a year. They have released a new version of the hardware kit, at least, which looks like it might work a bit better, and provided better instructions on building it.

Ok, thanks for the honest evaluation!

Guess its time to start trying to convince myself I could actually get a decent ROI on the Passport.

Thanks Again,
Michael

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ToyKeeper wrote:
sixty545 wrote:
I hope that a piece of plastic will solve it for you.

I should probably try that too. Smile

I had been thinking of trying to attach a really white piece of paper or something at a 45 degree angle and bounce light in, but it’d be physically a lot easier to just stick a translucent sheet of something on the front of the measurement device.

I have some stuff packed away somewhere that might work well. It’s a diffusion filter used in iPhone touchscreen/LCDs. Helps to equally disperse the light from the 4 or 5 LED’s mounted on the perimeter. Works really well at diffusion, will turn almost any light, even those with fairly tight beam, into more of a mule style beam pattern, all spread.

If you think that might help I’ll try to dig through my packed away stuff at storage and find you some.

-Michael

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vestureofblood wrote:
We may be out of lux on that premix even if they do contact me back. I just found this on another site $500-$1200?
http://www.labspherestore.com/SearchResults.asp?Search=6080&Search.x=8&S...

I am thinking if that is the case I may try to make some. Here is where I found out that it was made from.
http://www.ncbi.nlm.nih.gov/pubmed/20068984

PVA is not that expensive, and Bariumsulfate is not that expensive, so I guess they just tack on an extra $450 buck for adding the word “Labsphere”????


Ok, I bought a bottle of PVA (it is sold as a mould release agent for polyester and epoxy) and did a first experiment: I made a mixture of 20ml PVA and 15 grams of BaSO4, which appeared a good thickness to apply with a brush (about the thickness of latex wall paint), and applied two layers on a flat test-piece of styrofoam, drying the first layer in the sun before applying the second layer.

Observations:
-it applies really easy in a thick layer, much better than the BaSO4-latexpaint mixture that I used before. The second layer applies well too without disturbing the first layer.
-the result feels very durable, it does not scratch off at all with my finger nails.
-it is even somewhat flexible, does not crack when the styrofoam is bended a little.
-the two layers do not let much light through: compared to the bare styrofoam (2cm thick), the light through the styrofoam+2layers is reduced by 80-90% (estimation by eye).
-the coating looks really matt, like you want it to be for an integrating sphere coating.
-for an actual integrating sphere coating I would use 3 layers, also to get a smooth finish.
-a very rough first estimate is that when applied like I did, for a 30cm inner diameter styrofoam sphere, you need about 500gram BaSO4 and 650ml PVA.

I have not measured the big questions yet: if this coating improves the reflectivity of a sphere (my former latexpaint/BaSO4 coating even reduced reflectivity compared to bare styrofoam), I have to test that in an actual sphere, but when shining a flashlight at various angles suggests that reflectivity may just improve a bit.

So far so good! Smile

vestureofblood
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Thats fantastic news. I am excited to see how it performs in the sphere as well.

In Him (Jesus Christ) was life; and the life was the light of men. And the light shineth in darkness; and the darkness comprehended it not.
http://asflashlights.com/ Everyday Carry Flashlights, plus Upgrades for Maglite.

vestureofblood
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djozz,

When you are using this setup and you take a light and move it in and out of the ball deeper does it effect the measurement? For example if you stuck the bezel of a convoy L6 in there like an inch deep?

In Him (Jesus Christ) was life; and the life was the light of men. And the light shineth in darkness; and the darkness comprehended it not.
http://asflashlights.com/ Everyday Carry Flashlights, plus Upgrades for Maglite.

djozz
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vestureofblood wrote:
djozz,

When you are using this setup and you take a light and move it in and out of the ball deeper does it effect the measurement? For example if you stuck the bezel of a convoy L6 in there like an inch deep?

Yes it does matter how deep it is in, but there is a maximum and that is what I take as the correct measurement. If the light is not deep enough in some light is lost that is not entering the sphere (thus a lower measurement) and when it is too deep, the flashlight body/bezel (usually black) is absorbing light and lowes the reflectivity of the sphere (thus a lower measurement).

These are not huge differences by the way, if you are in about the correct position and move the flashlight a few mm in or out, the reading stays well within a percent.

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