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Green Screens and Lemons : Case study on complex greenscreen cleanup

green screens and lemons

There was a time, when shooting sequences on green screen, and creating avatar type films was the domain of large production houses. With dedicated studios, and armies of vfx artists to make it all come to life. 

Fast forward approximately 10 years, and green screen shots are everywhere, from news studios, to cheesy Bollywood tele-serials. The quality may be somewhat questionable. 

Bringing this into my own experience, I was recently approached by a video production company that works in the music industry, who had promised one of their clients, a full scale green screen shot video, that would catapult them to stardom.

I began my career working in film, one of my most cherished projects, is a green screen piece I did with a pair of music video producers, a few years ago now. In a similar vein they'd approached me with green screen footage, with the brief of creating a short romantic type clip, with the LA cityscape as a backdrop by night. To be completed in 2 days. We somehow managed to get an extension and around 3 or 4 weeks, and had something beautiful, and romantic to show for it.

A pair of star crossed lovers gaze upon one another from the top of two glass towers, in the LA cityscape, stars twinkling under the glow of a full moon. They run towards one another and leap from the buildings.. Embracing mid air within the night lit skycrapers of downtown LA..  

The directors, were experienced videographers, they'd hired a studio, through contacts they had at MPC, and had shot a beautifully lit green screen. With some nice camera moves, and a few un-intrusive tracking markers.

The bulk on the work involved building a night time LA, texturing thousands of individual lights in the Figueroa tower, and other buildings, to make each light look unique. Creating a rooftop, which reflected that beautiful ambient light coming from the environment, and a beautiful, night lit scene of the LA skyline.  

So when I heard the word "green screen" shoot.. My ears pricked up and the excitement of creating something beautiful, caused a wave of excitement to rise in my core. 

In the initial conversation with the client, I was informed that they wished to go with a dark creepy feel, they "had" camera moves and 8 shots on green screen to be comped on an abandoned old Western style environment, that I was to create. All done within 4 weeks. Sounded doable.  

In my mind: track shots, 1 to 2 days;

Green screen clean-up: 2-3 days

Environment creation: 2 weeks

Setting up comps and colour correcting final grading, refining, 2 weeks

All planned sorted, deliverable?.. - Yes. 

Contract signed, storyboard seen.. And we have liftoff. I get all the footage on a disk, DHL'd from Hamburg. I've started on the 3D Western set, got a saloon model, a few others, and we're rolling..

That evening I plug the disk into my machine, to look at the shots.. I don't see any camera moves, its all static camera.. And a green screen with 100 RED markers. The actors are pale, blonde haired.. My heart sinks.. And I think oh my God.. Something is very wrong. (To provide a little context, green screen separate the actor from the background, to make them easily isolatable. Tracking markers, are used to trace the motion of the camera used on the green screen shoot, this data is then replicated in a software package, to plot the motion of the real life camera which can then be used to render the 3D to match the live action footage.)

Tracking markers are then usually just cleaned out with a process called "paint" where the compositor paints them over in the same colour as the green screen. So you have one universal green colour all across the background. On a standard shot you'd have 8 to 10 tracking markers maybe more depending on how complex the camera motion is. They're usually, a neutral colour, like white, yellow, so they're easily separated if need be from the green screen.. To be non intrusive. 

In this instance we had 100 markers, in RED. Now this poses a massive problem, as when you separate the red hued skin tones of the actors from the green screen, the tracking markers are also picked up. So they're hard to isolate. As a result one solution which is very labour intensive and time consuming, is to, manually paint out any offending markers. But when you have100 red tracking markers, you end up with an end product which looks like a blonde haired actor, who's being chased by an array of measels type spots. :D 

To make matters worse they'd tried a creepy lighting scenario with one strong keylight, from the top.. This meant in addition to all this the green screen was unevenly lit. Not great news. As it means the hues of green on the green screen vary significantly. 

Given my deadline of 4 weeks to complete this, I was slightly exasperated. I got on the phone to the client and asked her if they'd sent me the right footage..

Her response was an emphatic YES!.. They'd worked with an "expert" who had advised them, that no camera moves were necessary, all you needed do was stick 100 tracking markers to a green screen, shoot a static shot, then give that to a vfx guy, who would then "animate" all the camera moves in.. And the expert had subsequently taken their money and disappeared into the wildernesses of Canada to travel.. Never to be found again. By them. 

I gave her the bad news, that cleaning the green screen wasn't a 5 minute job, more like a 20 hour job, as I'd need to clean up any tracking markers that fell behind the actors long flowing curly blond hair, her dance moves etc. Multiply this by 3, for the Bass player, the drummer, and the harmonica guy.. Then multiply this by 8, for 8 shots.

(They'd shot each individual band member separately, to be brought together in each shot in a different position, and then have the camera dolly pan zoom around them). 

I also gave her the bad news, that the only thing possible in 3D with 2D flat cutouts, is usually a zoom, and at best a minor pan of the camera, so that you don't see that the 2D character is a flat card..  

Another reaction that you get from clients in these situations, is that they blame you. They've spent money on an expert, who's given them bum advice, disappeared, and you need to fix it!.. I've found in my role as an artist, that around 30% of my time, in some cases more, is spent on managing emotions. This means actively listening, understanding, then offering a solution, that is acceptable, even though in your own mind you may be panicking and sweating over how you will get all this done. If the 3D stuff doesn't work out I can always become a therapist.. :D 

Fast forward from this, I spent a few days rotoscoping/painting tracking markers out of long curl flying blond hair, building a 3d set, and thinking of ways I could shorten this whole process, to hit the promised deadline. 

I'd done a few nuke/compositing courses years ago, where the lecturer talked about working on nightmare green screens. It was a 10 year old course but I revisited it. And picked up a few ideas.. Nothing described my problem, with the measels like tracking markers..  

After a few sleepless nights, I somehow managed to find a Keyer, that would hit the red markers, I could then suppress the skin tones from that, and then add that to my green screen, and only roto/paint, maybe 10% of the markers out. This drastically reduced my time on the task, and it was all go from there. 

Yesterday I delivered the work, not a tracking marker in sight. A beautiful eerie Western style series of shots with green screen characters, sometimes teetering badly on 4 inch heels.. Vfx can only do so much.. We create magic. But magic has its limitations. They're usually budgetary though. 

In all this one lesson I took away, it was from the lecture I'd seen 10 years ago, where the presenter said:

"The best artists, don't get everything perfect, though this is a massive temptation. They deliver work as fast as possible, to hit deadlines. this sometimes means thinking outside the box, and using unorthodox methods. It has to be good enough " 

With more and more producers with access to high end cameras and green screen studios, there will be more poor souls who spend what they feel is a large amount of money, on expert advice, which is in some instances, not expert at all. Just delivered from someone very convincing. We'll get the thankless task of unravelling the tangled mess created by these experts, so that the life savings of the person who has invested in this don't go down the drain. 

A breakdown is viewable here: http://www.georgenischal.com/3d-models/film-vfx.html