April / 2012

Tech Column
Reflecmedia’s Chromatte and LiteRing:
Green Screen Without the Green Screen?

by Sarah Moffat

We all know that chroma keying is a technique for compositing, or layering, two images together. It is more commonly referred to as green screen or blue screen, wherein a colour range is made transparent, revealing another image behind. Lighting chroma key has always required light for the screen and the subject separately, while watching out for green or blue spill onto the subject and an even spread of light across the background. This can prove to be tricky depending on the tools and space you have to light. That is until Reflecmedia thought up a reverse approach.

Chromatte and LiteRing will change the way you handle chroma key shots forever. Think bicycle reflector tape. Now think of a giant piece of it. That is what Chromatte looks like. Chromatte is a fabric designed specifically for use as a background for chroma key production. To the eye, Chromatte is silvery grey, and when you move around a Chromatte curtain you see the reflective surface shift with ambient light from wherever your angle of view is, it’s really interesting, actually. LiteRing is the counterpart to Chromatte, it is an LED ring light, in green or blue, that sits on the end of the lens. The fabric contains millions of tiny glass beads that act as reflectors so when the directional light from the LiteRing hits the fabric, it is returned on the same path back into the camera's lens. This retro-reflective process means the camera “sees” the apparently grey fabric as a perfectly even blue or green background. The fabric is cotton-based and has around 70,000 beads per square inch! The glass beads are back coated with aluminium to give them their reflectivity. This also means the camera lens angle of view does not have to be straight on at the curtain. It can be at any angle and the beads still reflect back evenly to the lens.

" Photo Credit: Sarah Moffat

I had a very successful and simple shoot using this technology. The kit is so small and easy to set up. It came with two stands and a partitioned rod for an 8x8 Chromatte curtain, LiteRing with various sized lens adaptors, and the light controller. I had it set up in five minutes! I caught myself starting to set light the curtain, as if it were a green screen – it was a default in my head. Remembering that I no longer had to light the background, I got to focus solely on the subject. It was very refreshing, in fact. Lining up the still life subject about 3 feet off the curtain and pushing the camera lens with LiteRing as close to the subject as possible, I wanted to get a sense of what the limitations were, such as how close the LiteRing could be before it would cast onto the subject.

I was pleasantly surprised. The lens was about a foot away from the subject with no cast from the LED. To help me achieve this, I used the LiteRing controller which acts just like a dimmer switch. It is powered off with any 12V AC or battery power supply, and runs from power to dimmer to ring. Controlling the intensity of the LEDs does two things: 1) It pulls back cast light on the subject if in close proximity; and 2) It intensifies the appearance of the “green” screen effect on the curtain. I found that in far, wide shots bringing up the LEDs on the dimmer made for an overall bright “green,” even background. While on close-ups, dimming down allowed me to get the lens right in there for macros, and hand-held shots on live actions, where the lens saw less of the curtain/background and therefore “green” intensity could be sacrificed. Also, the obvious upside is that you are using fewer lights overall – save rental money, electricity, the planet, and it doesn’t get as hot on set. Makes sense to me. I am not sure of the large-scale application of this as I haven’t shot the next Matrix yet, but there is a challenge for anyone in chroma key feature land.

A quick note on reflection in the eye - I also shot a person in frame for a test. At about 3 to 4 feet away from the subject's face no visible green ring light reflection appeared in the eye. When freezing a frame in post and zooming into the face, I could see a tiny green speck at the edge of the pupil, however the dominant light reflection was that of the key light. A suggestion would be to pull further back, dim the LEDs, and use a longer lens to avoid any potential green ring light reflection in the eye.

Now, the real part of the test was in post— how well does it actually key? Amazingly well, fast and clean! Jim Hardie, an industry expert in post, says it’s the best key he has ever seen. I used FCP, a Chroma Keyer tool. Using the eye dropper, I grabbed only one spot of the green background, tweaked the range of options – greens, luminance, etc., and presto! The key was complete and clean. Edges of the subject were perfect. I was doubly impressed as the still life subject I shot was a fresh bloom of orchids, which have green parts to the buds, and stems. Yet despite the close proximity of the green LED while shooting, using the LiteRing dimmer and a bit of countering light source on the orchids, there were absolutely no issues in post of trying to separate only the green background from the green tones on the flowers. It truly was a snap!

A great example of the literal flexibility of this technology is in the first Harry Potter film. Remember Harry Potter’s “invisibility cloak”? Well, that was the early development of Chromatte and LiteRing. The technology itself has been around since the mid-1990s and stemmed from an idea created by the BBC and developed by Reflec, a UK company. Reflecmedia was set up in 2001 to bring Chromatte to the mass market. Technically Yours Inc. (TY) has been the exclusive Canadian representative since 2009. You can contact Jennifer Mallette there for use of Reflecmedia products, and yes, there are even more tools!


Sarah Moffat’s camera experience includes motion picture and still photography. She has worked in drama, documentary and live broadcast.

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