DIY LiteRing Chroma Key POC

Hey all,
the other day I got intrigued by the idea of crafting my own version of the light ring based chroma key systems.. I did some digging..

If you dont know what Im talking about, check out the high end reflectmedia

http://www.reflecmedia.com/education/media/video-gallery/litering-camera-action.htm

$2500 for a setup..

A better priced knock of can be had at

http://www.bhphotovideo.com/c/produ...0_KIT_CKL_200_Dual_Color_Chromakey_Light.html

The trick here was figuring out what the backdrop was made out of... retroreflective material.. once I got that far, I found a 3M supplier that sent me a 12" x 9' sample.. pretty cool, until today I wasnt sure I had the right stuff.... so I spent a few minutes, with what ever leds I had lying about, I set this up in about 15 mins..


(sorry about the strangeness in the first few seconds.. )

https://www.youtube.com/watch?v=86XH2cypiNA

Here is a quick keying attempt.. Iv never done keying before..

https://www.youtube.com/watch?v=UxlB_E-m6o0

Now, that fabric is very expensive, about $35 a yard, so its still too rich for my blood. But you can save a LOT of money doing it your self if you want to try this. I am looking for a knock of supplier out of china....


EDIT: So the shadow was made WORSE by being balanced for sunlight, and not florescent... in further tests, the shadows are just another shade of green (not brown like this example) and caused only small issues in keying.
 
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Within the colorspace, there are 3 colors... in an RGB (Red, Green, Blue) system, the colors have values from 0-255.

0 is no information in the channel, 255 is full, 256 is clipped and remains at 255.

So, if they are using the blue channel to pull their key, the white is actually comprised of R:255,G:255,B:255 - so the blue value in white is indeed the same as a pure blue sample - R:0, G:0, B:255.

I'm not sure what color space AE + Keylight work in, final cut is a YCrCb system (luma, then an x,y vector on a color wheel labeled Chrominance).

For keying DV (4:1:1 or 4 sample of Y for every 1 sample of Cr and Cb - so more rez in the Y), I like to work in YCrCB as the Chroma (CrCb) can be blurred slightly without destroying the crispier edges that are held in the Luma (Y) portion of the image.

How's that for an explanation?
 
Dreddy,
The retailer I contacted had 3M send me the sample. No direct link that I know of. You might try calling 3M directly.

What your looking for is

An engineering sample of "3M Scotchlite fabric - 8910"

My search for an oversea supplier has yielded fruit, though I wont know exactly what that fruit smeels like for a few weeks ;)

As Iv gone though a lot of trouble lining up the suppliers for my "prototype" I'm toying with the idea of punting together a "kit" of parts, and selling those at a smallish mark up.. The big expense right now is the fabric, hopefully the stuff on its way from china will work as well as the 3m at a fraction of the cost.
 
Well, shave that scruff.. and well.. sorry no.. it wont work.. :P

Sure, my cost is about 2$ for a square meter. Minimum Order 1000M. :) do the math... Now, hes doing me a favor by allowing me to order a smaller quantity for a prototype. Also, I don't have much to go on that it WILL work, but from what I can see.. its about the same stuff..
 
wait, thers still more! ;)

The china stuff should be 1M wide.. the 3M stuff is 50"

Im thinking Ill be putting together a DIY kit, with the ring light parts and the material.

For this small order Im paying well over the $2, but MUCH less than the 3m stuff. If It works, and there is enough interest, maybe I can get this guy to sell smaller lots? Lets see how it goes.. first I gotta actually GET the stuff here. Certain amount of trust required.

So for my test above I used 12" wide strips gaff taped together. The 3M stuff has a nice polyester backing so it should be machine workable. I dont know what this stuff from china has for backing..

I was thinking that gluing it down to a substrate, like a big plastic tarp, might be a good idea. Iv read on the OTHER products web sites to use the 3M tape to cover any seams. Though, I cant see any seams on my edge to edge taped setup, though, Id say with use the edges would come up.. any great seamstresses know how to get an invisible seam without any gather and not require an iron?
 
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so the Chinese fabric arrived yesterday. Its only a BIT different, and in some of the technical aspects might even be BETTER than the 3M. Though it doesn't reflect as brightly (very minor diff, hard to even notice.. ) The Chinese material is "darker" when not reflecting, which I think has a better "look" and better off axis light rejection..

Where the 3m excels is the backing. The Chinese stuff feels like thin winkbreaker or stop-rip nylon material, very light weight, whereas the 3m has a heavy polyester backing.

Im picking up a tarp at Home Depot today, and try and glue the Chinese fabric on to the tarp. Also, my wifes going to try and sew a few lengths together to see how that turns out. Im thinking a combination like sewing and gluing to some lightweight backing material will be required to get any kind of "durability" out of the stuff.

In othe news, the light ring prototype mark II works much better, even in outdoor light. I have 16 Pirana LEDs' super glued around the outside of a 72mm Lens hood, using step rings to get down to the 58mm thread for my lens.

The use of PWM dimmer is pointless.. It works fine, dims the light, but it does so by "reducing the duty cycle" of the LED's in other words by "flickering" which of course is picked up by the video cam as a rolling line.. unnoticeable to the human eye, but definitely shows up on camera. Im not sure dimming is a real necessity anyway.. thought all the competing products include that ability.. so there may be something to it. I do note that real close up work might benefit from a dimmer light.
 
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