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Author Topic: A fair way to compare blade lighting  (Read 1953 times)

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Offline profezzorn

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A fair way to compare blade lighting
« on: September 02, 2016, 02:24:34 PM »
I now have 4 blades for my home-built saber, and one store-bought. It's easy to take a picture to show which one is brighter, but the pictures never look like the blades actually do in real life. I also find that unless you have two blades on at the same time, comparing their brightness is very difficult.

So, today I ordered a pantone huey, a cheap color measuring device. My intention is to 3d-print a small black baffle to hold the sensor in a consistent way compared to the blade, and if need be, include some filters so the huey doesn't get overloaded. Then I can measure light and color at the base of the blade, in the middle of the blade and at the tip of the blade. I can also make sure that light is evenly dispersed in every direction.

Hopefully the results will not just be informative, but also reproducible, meaning that if I measure my saber using this device, and someone else measure a saber they built with a device they built, the results will actually tell us which is brighter. Anyways, I'll post progress, results and designs in this thread, and if anybody have any particular advice, thoughts or encouragement on the matter, please let me know.

Offline profezzorn

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Re: A fair way to compare blade lighting
« Reply #1 on: September 09, 2016, 09:53:31 PM »
Got my pantone huey today ($25 on ebay) and played around with it a little.
I don't think it needs any 3d-printed baffle or anything, just press it against the blade and measure.
The huey has R, G and B sensors, but the colors don't line up very well with the LEDs in my blade. I started with my PL9823 blade, and measured the red, green and blue colors separately:   (I used a command called spotread which was already installed on my linux box.)

R measuredG measuredB measured
red6532510.2
green318933142
blue4553242512

I also measured my screen, and got 292, 274, 341, so clearly the blade is brighter than my screen. :)
I also measured yellow, cyan, purple and white, and the values where basically linear combinations of the rows given above, like you would expect.
I'm not sure why the blue value is so big, I don't think it really means that the blue is super-bright, because it's not really super-bright.

When I measured my simple string blade, I got 1408, 1192, 5351.
My LED adapter + trans-white blade scores pretty good: 1708 1235 6458 near the base, but only 313 102 1689 at the darkest spot.

Finally, the LED strip blade:

R measuredG measuredB measured
red14035860.4
green7231784147
blue7855304420

I think that pretty much sums it up: LED strips FTW.

Offline profezzorn

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Re: A fair way to compare blade lighting
« Reply #2 on: September 10, 2016, 09:41:47 AM »
I forgot to include readings for my "black series luke skywalker force fx" saber: 60 49 335

I think the huey returns linear readings, but visual appearance is more like the cube root of something, which would mean that my LED strip blade appears to be about 3.6 times brighter than the force fx saber in the blue spectrum. (sqrt(4420) / sqrt(335) ~= 3.6)


Offline profezzorn

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Re: A fair way to compare blade lighting
« Reply #3 on: September 10, 2016, 10:22:21 AM »
Got a blade from Vader's Vault today, sanded and with blade film.
I measured it with my LED star adapter and got: 1777 798 8638 near the base and 614 203 3305 at the darkest spot.
Much better than my trans-white tube, and pretty impressive brightness, but a fair amount of unevenness.
« Last Edit: September 10, 2016, 02:27:52 PM by profezzorn »

Offline profezzorn

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Re: A fair way to compare blade lighting
« Reply #4 on: September 10, 2016, 02:44:52 PM »
I'd like to point out that while these readings are useful, they don't necessarily tell the full story of blade brightness...

  • These are spot readings, that means that you have to multiply by the surface area to get the total light output. IE, a 1" blade and a 7/8" blade might have the same reading, but the 1" blade would put out more light total. Same thing applies to the length of the blade.
  • The color sensitivity of the huey is probably tuned to be similar to sRGB, this means that very deep colors might produce smaller numbers than less deep colors because the huey is not as sensitive to it. We could compensate for that if we knew the sensitivity curve of the huey.
  • I'm not sure exactly how different diffusion methods affect the accuracy and fairness of the readings. Like, if I have a clear thin-walled blade and a clear thick-walled blade, both with perfectly diffused interiors, would the readings be the same or not?  I could probably figure this out mathematically, but I have not done so yet.

Even given these caveats, I think that the huey is a much better tool for comparing blade brightness than photos will ever be, as it is nearly impossible to take pictures of lightsabers that accurately convey what the blades actually look like.  I'm not saying that photos and videos aren't helpful, I'm just saying they aren't very accurate.
 

Offline Sincenatic

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Re: A fair way to compare blade lighting
« Reply #5 on: September 11, 2016, 02:25:01 PM »
Taking photos on a lightsaber in darkness is probably most about showing how cool the saber looks like… in darkness… on photo… with that particular camera, and I guess that accuracy is not much of a concern. Taking photos indoors with the lights on is a step towards accuracy, but the camera will still not capture the colors correctly. A reflection in a glass-framed painting in the background can sometimes reveal more accurately the colors. If accuracy really is an aim of the photo, I recommend photos outdoors during daytime, but in shadow. In all of these cases a reference point with alternative sabers provides more information and a written description can put the photo in perspective.

A pantone huey is interesting, but I find it very difficult to imagine how three RGB values actually looks like. Higher values are of course brighter, but how a combination actually turns out is difficult to visualize. When accuracy is the purpose, I think it would be good to combine as many descriptions (and data) as possible; photos in different conditions, with reference points, with explanatory texts, and using tools, like a pantone huey and a luxmeter.

Offline BATMAnakin Skywalker

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Re: A fair way to compare blade lighting
« Reply #6 on: January 19, 2017, 02:53:32 PM »
This is awesome! Thanks for this research. I wish to attempt something similar. I did not have much faith in the neopixel LEDs being bright. On your regular string LED blade, which LEDs are you using?

Offline profezzorn

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Re: A fair way to compare blade lighting
« Reply #7 on: January 19, 2017, 04:13:57 PM »
It's a Blue-Blue-White tri-cree 7/8" star from TCSS.

Offline BATMAnakin Skywalker

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Re: A fair way to compare blade lighting
« Reply #8 on: January 19, 2017, 04:22:44 PM »
It's a Blue-Blue-White tri-cree 7/8" star from TCSS.

Sorry for the confusion! I was referring to this one:

Quote
Finally, the LED strip blade:

R measured   G measured   B measured
red   1403   586   0.4
green   723   1784   147
blue   785   530   4420

Offline theholyduck

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Re: A fair way to compare blade lighting
« Reply #9 on: January 19, 2017, 09:32:37 PM »
Here are instructions and info on his LED strip blade (also on that sitte the neopixel blade. string blade and in hilt emitter. )