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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thanks for you info, i bought 4 sheets 1yardx39" from the Canadian ebay user (50 euro shipped). When i will have everything in my hands i will setup and test it :)

Glad I could help. My Vimeo statistics show a huge number of views of the video from Italy. Any idea as to why there would be such a specific interest from your country? Since you just joined the forum I'm assuming you learned of the project from another source.

I also got some of the 39" fabric and it works pretty much the same. My setup doesn't produce the best results unfortunately. I'm using fluorescent lights in my basement. If my planned Web site about the tests comes to fruition, it would be nice to feature international results as well.
 
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about dimmers..

the PWM (pulse width modulation) method of dimming LED's can cause your green screen to oscillate or flicker like a TV screen or Monitor will on camera. The one I have does at any rate. You cant see the flicker with the naked eye, but your camera will pick it up. You can also manipulate this behavior with shutter speed. I don't know if different PWM dimmers work differentially, there may be some method of PWM techniques that allow for dimming without pulsing so slow that it is detectable on camera... any ideas?

michaelmanch, did you FILM your screen as you move the dimmer from off through its range to full on?

Thanks
 
Glad I could help. My Vimeo statistics show a huge number of views of the video from Italy. Any idea as to why there would be such a specific interest from your country? Since you just joined the forum I'm assuming you learned of the project from another source.
we are talking about the diy-led-setup in the italian video makers forum and i started my kit after reading your post. ;)
 
about dimmers..

michaelmanch, did you FILM your screen as you move the dimmer from off through its range to full on?

Thanks


The idea for the dimmer came from the company's Web site. It proved to be necessary for me. Without the dimmer the led ring is at full brightness. I discovered that as I increased the brightness of the ring, it bled over the lens affecting the exposure of my image. The brighter the light ring made it the darker I became. See the following image showing the changes by increasing the percentage of the led brightness from 25% - 100%.

I am not a technical wizard and fully realize that I could be doing something wrong and welcome any input to improve my situation.

led_bleed.jpg


My most baffling experience has been the halo effect that I get. This is not a shadow as some may suspect because I am sitting too far away from the screen and it is consistent all the way around. I visited the Reflecmedia Web site and viewed some of their videos and this doesn't seem to occur with their system. Proper lighting may again be an issue.
 
halo looks like shadow, move your subject away from the screen to help it go away.

as for exposure, auto will adjust to the primary value's brightness... in this case, the green... the brighter the background, the darker the camera goes to make up for it.
 
I had hallo like that until I took off my 35mm adapter.. are you using any filters, etc..

also, I think there is some relationship to the position of the light ring relative to the most forward glass element. Can you move the ring forward\backward?

I never found the halo to cause keying issues anyway..

My work flow for exposure is to turn OFF the LED's, light the shot, adjust and lock camera exposure, with the green screen lights off! Then just turn em on and film. Obviously requires manual exposure, or at least a way to LOCK it ...

Cool stuff.
 
FWIW, The flicker Im talking about would NOT be visible with still images.. can you upload the 25% take to youtube?

I assume the reason I can't embed video is because I'm just a basic member. I tried YouTube as well without success. Can't afford to upgrade right now.

Here is a link to the video of the dimmer on approximately 25% brightness. I can't see any flicker.

http://www.vimeo.com/17809076
 
Thanks Michael,
I dont see any flicker either.. I wonder what other factors might be in play or if there if the product I have is just a bad design?

Enough evidence for me to order one like you have, and give it ago..

Vimeo doesn't embedded on this site for anyone (something we all complain about on a regular basis)

For youtube you just use the string after the equal sign in the link..
to embed this video..
http://www.youtube.com/watch?v=[B]F...ou would use [Y T] [B]FdxvBODVD_Y[/B][/ Y T]
 
I had halo like that until I took off my 35mm adapter.. are you using any filters, etc..

also, I think there is some relationship to the position of the light ring relative to the most forward glass element. Can you move the ring forward\backward?

I never found the halo to cause keying issues anyway..

My work flow for exposure is to turn OFF the LED's, light the shot, adjust and lock camera exposure, with the green screen lights off! Then just turn em on and film. Obviously requires manual exposure, or at least a way to LOCK it ...


I appreciate you describing your work flow, unfortunately that's a much more professional setup than I am able to pull off at this point. But I haven't had too many problems with keying. Just not as good as I'd like. The poor quality of my lighting is a bigger issue.

I have a Canon HV30 with no adapters. The lens is adjacent to the camera body and so there's no room for the ring to move forward or back. There's only half an inch of space for it to sit.

There are manual adjustment options and I have tried various settings, although I had the light ring on at the time. It never occurred to me to keep the light off. I will need to do more experiments now that I know to make changes before turning on the led ring.

It would be great to have a better camera and studio lights instead of the fluorescents I have positioned on either side and above.
 
thanks for that detail Michael, I would have missed that..

The HV30 is no more or less pro then my camera, hfs100. You just need to lock the manual exposure before you turn on the green screen lights..

Ill send you a PM with a link to how to trick your camera into exposure lock..

My lights are all cheap Smith Victor used stuff, some from Goodwill others from craigslist, my two phtotoflods under $100.

Heck if I were in tormnto Id get these.. http://toronto.en.craigslist.ca/tor/pho/2111651468.html
 
You don't have to quote yourself, although doing so makes you META! How much space is there between the subject and the screen? 10-12' ? We're dealing with angles here, so the distance between the camera and the screen defines a cone whose center is blocked by the subject. If the subject is farther back, their distance in relation to the camera and the screen can create the shadow.

I would recommend:

Controlling the light by surrounding it with a ring that directs the light more forward (this could also be achieved by recessing the LEDs a bit into their respective holes -- one of the advantages of building your own)...

Then place your camera 20' from the screen and shoot tests with your subject at different distances from 8' from the camera - 16' from the camera and see what gets rid of the shadow for you. Try this without any other lights in the shot, so all we see if the screen and the shadow without any other interfering lights.
 
A test video using glass, bubble wrap and "hair" alternating between the original green screen and the keyed footage. The bubble wrap was more opaque than I would have liked but it's still surprising how effectively the original color was removed.

https://www.youtube.com/watch?v=c0ySdHjXz-c
 
thats pretty impressive. How did you key out the stuff behind the bubble wrap without keying out the bubble wrap. (if that makes sense)

I didn't do anything special to that shot. I didn't even key that particular footage separately. Since the glass, bubble wrap and hair were all filmed under the same lighting conditions consecutively, I keyed the glass, made some adjustments and then copied the settings onto the bubble wrap and hair footage.

Perhaps the software I am using for keying, Keylight 1.2 within After Effects CS4, is especially good at this. I think it's reasonable to have assumed that the bubble wrap would have distorted the green color such that the software wouldn't have been able to match that to the green keyed somewhere else on the footage. The level of sensitivity was certainly unexpected.

It makes me wonder about what conditions would be necessary for it not to work. Due to my lighting, I had to tweak settings within the glass footage to make things clearer and that causes the glass to disappear, although some reflections can still be seen over the background. That could have been done better.
 
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