Reflecmedia Cromaflex: The Grey Green Screen

Litering and Chromaflex screen

The Grey Green Screen: Part One

When I joined the CADARN team in May 2014 one of my initial responsibilities was to familiarise myself with the equipment that had been bought for the project’s various partners across Wales. On my first day, I was shown to a store room where Aberystwyth University were housing their kit. As I looked through the various bags of cameras, lights, tripods, and laptops, I came across a large circular bag and asked my colleague Geoff Constable, CADARN’s Liaison Officer, “What’s this?” 
“Oh that’s the ChromaFlex screen,” he replied, “it’s a green screen kit, but we’ve not figured out how to use that yet! Hopefully you can get your head around it”. 
I unzipped the bag for a quick peek and thought to myself… that’s not a green screen, it’s grey!?!? 

At first glance the ChromaFlex screen seems illogical. How can a grey screen be a green screen? The answer is all in the name of the company that produces the screen, a company that has revolutionised chroma key technology: Reflecmedia

Traditionally, when filming a chroma key shot, you’d take your subject and place them in front of a vivid colour backdrop, usually blue or green. You’d then shoot your scene and take the footage into your editing software to apply a chroma key filter to remove the green or blue background colour.

Reflecmedia have replaced the traditional coloured screen with their ChromaFlex screen, which appears grey under normal lighting conditions. However, on close inspection you notice it’s made up of millions of tiny glass balls, very much like the material on a hi-vis vest. These  tiny balls reflect any light shone directly at the screen, back to the source (imagine the headlights of a car falling upon a hi-vis vest worn by a cyclist). CADARN had purchased several Reflecmedia ChromaFlex All-in-One Studio Bundles, and it was my job to demystify the technology and then train others how to use the equipment.

Litering and Chromaflex screen

Aber Academy Media Lab with Reflecmedia kit set up.

The biggest problem I faced was that I'd never worked with this type of green screen technology. I’d used traditional green screens in the past and I knew that they took a lot of time and effort to set up and light correctly. I was intrigued by everything I’d seen and read about the ChromaFlex screen, but the whole thing sounded too good to be true! 

The kit is made up of two key components, a grey ChromaFlex screen, which forms the backdrop behind your subject, and a LiteRing that you attach to the lens of your camera, and this can be switched between either blue light or green light, depending on the circumstances of your shoot.  There are stands and lights and other parts to the kit, but the real magic happens when you turn the LiteRing on and shine it at the ChromaFlex screen and the coloured light is reflected directly back to the lens of the camera. As if by magic your subject is suddenly standing in a field of vibrant colour as opposed to a dull grey backdrop! You really do need to see it to believe it!

The first step in demystifying the ChromaFlex screen was to set it up and work hands on with the technology, so along with my CADARN colleagues Lizi Hesling and Matt Cawte, we assembled the kit in the Aber Academy Recording Studio in Aberystwyth University. We began by setting up the ChromaFlex screen which is quite large (approximately 2m x 2m), easily tall enough to accommodate a person standing in front of it.  Although it was fiddly the screen went up easily, and as the studio is quite small, we chose not to use the stands provided, opting instead to simply lean the screen against the wall. 

Camera and Lightring

The LiteRing attached to a JVC GY-HM150E camcorder.

Next we set up the video camera on a tripod and attached the LiteRing adapter to the lens. Once the adapter was in place, we were able to attach the LiteRing. We then set up some studio lights to illuminate our subject (in this case, Lizi), and with everything plugged in we were ready to power up! 

The first thing we did was test how the screen performed at different intensities. We started off at the highest setting, which resulted in an over-exposed image. It was so bright that the ChromaFlex screen appeared as pure white rather than green in the camera’s LCD monitor. We dialled the intensity down incrementally until we got to a satisfactory level at the low end of the scale around the 7-10% mark, where we began to see a good even green background on the camera’s monitor. 

Lizi in front of Chromaflex

The LiteRing set at three different intensities. The top is too brigh, the bottom too dark and the middle is just right.

Once we’d established the optimum intensity of the LiteRing, we began to test the positioning of our subject in relation to the screen and the camera. Traditional green screen set-ups usually require a large gap between the subject and the backdrop to avoid shadows. But with the ChromaFlex screen, this isn’t an issue, because the LEDs on the LiteRing are so bright they wash out any shadows. 

We asked Lizi to stand close to the screen and then she gradually moved towards the camera while we monitored how her position affected the result we were getting. Due to the configuration of the LED bulbs around the LiteRing, we noticed a very subtle halo around the edge of the subject, which changed in width as she moved. Following a little investigation, it turns out that this halo effect is perfectly normal and keying it out in post production was an easy process.

Once we’d recorded our tests, Matt took the footage into a variety of software packages to see how effectively the kit had performed. Our first test was in Adobe Premiere Pro CS6 which offers a variety of chroma key effects, however we found that the ultra key effect was by far the easiest to use with minimal fuss and it also gave us great results. Matt also took the footage into After Effects where he applied a key light effect which gave him even more control over the colour separation. Finally, we took the footage into WeVideo, which has a very basic colour key tool.  Although it did the job, it wasn’t as effective as the effects we used in the other software we tried. 

In all our tests we found it difficult to get a sharp, clean key around the edge of Lizi’s hair. A good rule of thumb when filming chroma key footage is pay particular attention to your subjects hair before shooting as you may encounter problems later down the line, especially if your subject has unruly hair (as we found with Lizi). To overcome this you should consider asking the subject to wear their hair pinned up or close to their head in order to minimise any stray hairs that can compromise the effect.

By the end of our first day’s testing, we agreed that setting up and working with the ChromaFlex screen had been relatively easy. But to achieve a good, clean key that separates effectively in post production you need to take time to make the necessary preparations before shooting to ensure everything goes smoothly. Don’t forget to factor in the time it takes to set up and take down the ChromaFlex screen and LightRing, and make sure your subject is aware of what to wear in terms of their clothing and hair to avoid issues when recording.

Working with the Reflecmedia Chromaflex for the first time. 

 

The Grey Green Screen: Part Two

Following our initial ChromaFlex screen test, I was asked by Aberystwyth University’s E-Learning Team to deliver an informal training session introducing them to the basics of using the chroma key equipment. 

In the lead up to the session, I did more research into both ChromaFlex screens and more traditional green screen methods. In doing so, I was able to gain a wealth of information on the history of the technique and quickly realised that there’s much more to using a green screen than I initially thought! 

At it’s most basic, it’s a technique that allows you to achieve average results very quickly and easily, but to fully utilise the power of the chroma key effect and produce professional-looking results you need ensure you take the time to prepare for a shoot. You need to account for time time spent assembling and properly positioning your ChromaFlex screen and any lighting you might use, and you also need to ensure you take care of small things like hair, make-up and props. And of course, after all this, the post production side of the process can take just as long! 

Initially, I planned to run the session with the E-Learning Team in the Aber Academy Recording Studio where I’d already installed a ChromaFlex screen. But I decided in the end to move the session to the Aber Academy Media Lab where we would have more space and everyone would be able to get fully involved in the process of setting up the equipment from scratch. I thought the hands-on experience would really benefit the group, allowing them to fully engage with the setting up of the kit and so be able to do it themselves in the future. 

A few days before the session, I collected the kit and assembled everything in the Media Lab to check how long the process would take from beginning to end. On the day of the session, I placed the kit in three separate piles and assigned different roles to the three attending members of the E-Learning Team. Kate Wright was given the task of setting up the lights, Susan Ferguson was responsible for assembling the ChromaFlex screen, and Mary Jacob was in charge of the JVC video camera and the LightRing attachment. I remained on hand to offer guidance and advice throughout the session.

Setting up the full Reflecmedia ChromaFlex kit.

With the kit assembled, the group gathered together to share their thoughts on the process. The overall opinion was that everything had been relatively easy to set up. There were concerns that users might be reluctant to use the kit due to the sheers bulk of it all, but as I pointed out to the group there is already a pre assembled ChromaFlex screen up and running in the Aber Academy Recording Studio, so there really are no excuses not to give the technology a go!

Then we turned the camera and the lights on, and I walked them through how to light the scene and expose their shot. Once this was done, it was time to work with the Reflecmedia kit. We turned the LiteRing on and I demonstrated how it worked in conjunction with the screen and the camera, as well as how to set the intensity of the green or blue light to achieve a good colour separation for post production.

To make sure the team got as much as possible out of the training session, I thought it would be a good idea to try and shoot a real green screen scenario. I asked them what they would like to do, and they settled on a weather report, which is probably the most common use of the technology that you’ll see. I had a still image of a weather map prepared, and showed it to them before we began so that they could imagine it behind them while we were shooting. Mary was in front of the camera improvising a fake weather report whilst Sue operated the camera. Kate then took on the role of the news anchor and we filmed her introducing and wrapping up the weather report, which we planned to use as bookends when we edited everything together.

Once we had our footage, everyone was keen to move onto the editing phase and learn how to apply a chroma key effect. After loading up Premiere Pro, I demonstrated how to import the footage and edit their sequence. Then I showed them how to apply Premiere’s ‘Ultra Key’ effect, which gave them a quick and effective colour separation with minimal tweaking. 

As a brief introduction to a complex piece of equipment, the workshop seemed to be a successful and rewarding experience for the E-Learning Team, who said they now felt at ease with the technology. There were questions and issues raised during the session relating to the size of the kit, and and the reluctance users might feel towards a technology that on first impressions seems difficult to use, and no doubt these questions will addressed as we all become more familiar with the CADARN equipment and the ways in which it can be use it to produce educational media. But hopefully staff members and E-Learning teams across the partnership will produce interesting work that will push both their own comfort levels and the boundaries of the equipment on offer! 

The final video produced by Aberystwyth Universities E-Learning Team.

For more information on Reflecmedia and on the evolution of greenscreen technology, take a look at the links below.

Hollywood’s History of Faking it - the Evolution of Greenscreen Compositing

Philip Bloom on the Reflecmedia Litering

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