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November 2014
Issue: July 1, 2007

GOING GREEN

By: Ann Fisher

Visual effects supervisors go to great lengths to be on-set during greenscreen shoots. One snorkeled, in his jeans, to check an underwater greenscreen music video shoot after an aboveground color monitor shorted out. One offers his company's presence as a free service. Another says he "begs and pleads" with recalcitrant clients.

That would be Beirne Lowry, creative director at Mr. Wonderful in New York City, who says, "I'm the one who's going to have to fix it in the end and be responsible for it. And there's so many things you can screw it up with. I want to be on-set. So many times they just go ahead, shoot it and figure we'll fix it in post."

As greenscreen shoots soar in popularity, this was never more true. Greenscreen usage is becoming increasingly popular because it is less expensive than taking actors on location, and everything from the weather to the lighting can be controlled.

"We're always onset for shoots we have to composite," says Alex Lindsay, founder/chief architect of Pixel Corps, a guild of digital craftsmen. "Partially because we tend to use our own camera, a CineAlta F-950 that shoots 4:4:4 and makes greenscreen work much easier. Secondly, it's important to have the compositors on-set because many DPs and technicians who don't composite themselves often seem to have superstitions about greenscreen that make the process much harder. They also, for good reasons, worry more about their issues than our issues, and we need to push back during the shoot to make sure we get the quality we need to produce the shot. For 90 percent of our shoots, we're managing the shoot, the CG background, and the composite."

Martin Gardeler, visual effects supervisor at Ghost Digital Production House in Denmark, says his company provides on-set supervision for free during jobs. "The client can't save money by not having us there. We have had many situations where they came back from the shoot with the strangest takes that meant 500 percent more work for us," he says.

"Mechanism Digital always makes sure there's a visual effects supervisor or at least senior visual effects artist working, depending on how complicated the shot is," says Lucien Harriot, owner/visual effects supervisor at Mechanism Digital in New York City. "It's a mistake to ask for a greensreen shot and let the DP shoot what they think [is right]. We have received greenscreens that were fine and sometimes we are brought into the job after it's shot but it can be a big chance to take. They might shoot something that's technically correct but we may have been able to make suggestions on-set that would make it easier, more flexible, cheaper in post."

Zack Nederlander, visual effects supervisor at Empire Studios in Los Angeles, gets on-set by also wearing the hat of lead compositor. "In preproduction I think about how I'm going to composite. Now people in the television industry and smaller projects think you just bring it into post after," he says. "I prefer always to be on-set. The greenscreen is one element and one challenge in a greenscreen shoot, but there are all these other elements of hot-spots, uneven lighting, shadows and, even worse, when there's equipment in the view of the camera. Even if they see it, a gaffer is not going to move a light unless someone tells them to. They're just trying to appease the AD and get it all set up as quick as possible. That's why I have to be there for quality control." (Nederlander is the one who snorkeled on-set.)

Visual effects supervisors want to check camera format, lighting and stage set-up to avoid all sorts of problems that will cost time and money in post.

CAMERA FORMAT

Camera format is the first red flag. "One of the issues of shooting HD with greenscreen is some of the lesser formats are basically unusable. It's almost better if they'd shot it on Digi Beta, then in a larger format like HD because there's so much noise," says Lowry.

Adds Empire's Nederlander, "We shot on HDCAM, not HDCAM-SR, nothing fancier than just standard HDCAM so, of course, we have image compression, color compression. It's a 4:2:2 format, the resolution is not true 1920x1080 so it's compressed visually. There's three to four different types of compression on it. It's not fun."

Mr. Wonderful's (www.mrwonderful.tv) Bernie Lowry did a greenscreen shoot atop a Times Square rooftop for the 2007 CBS Sports NCAA Final Four open that aired in February. The first thing he checked was the camera format. "I wanted to make sure it was a high-quality, uncompressed camera because that's essential to getting a good key," he says. They used a Sony HDCAM 900, a broadcast standard HD, not consumer, format.

Lighting was critical to make the greenscreen a rich, deep green, "elfin green, like the Keebler elves," he says. "A lot of times greenscreen gets lit where it's washed out and bright, hot spots totally destroy it. You need chroma with greenscreen. It's not the brightness; it's the amount of chroma of the actual color green coming off there. You're just keying green — whatever software you're using is looking for the G in RGB." Another thing to check was the actual greenscreen fabric quality; in this case, the thicker, matte quality passed muster.

The greenscreen shoot for this :60 CBS open was done under ridiculous conditions, on a roof in February's bitter cold, howling winds, at night. But that's where Ludacris performed, as the crew and many sandbags held down the 12-foot-high-by-25-feet wide greenscreen. Lowry was a little concerned about greenspill since Ludacris was only a half dozen feet from the backdrop but soft, smooth, even lighting helped. Another concern he worked around was Ludacris' skin tone. "He was wearing a red hoodie which really helps when keying on greenscreen but people of color are a little harder to shoot on greenscreen. Sometimes the darker skintones reflects the green a little more — there's a little more green saturation. Norwegian people are actually easier to key off greenscreen. I used to do a lot of basketball work," explains Lowry.

He was also the compositor, working on Flame running the Linux kernel, using a moduler keyer that let him sample grain. "It's an extra step you have to take but it's one other level of keying and noise reduction. I find that's really useful. It makes good keys look way better and it makes unusable keys barely usable."

LIGHTING

Onset, visual effects supervisors focus on lighting because often it may counterbalance the format compression issue. "Panasonic DVCPRO HD cameras are becoming very popular with networks and budgets that can't afford film but are looking for HD," says Lucien Harriot of Mechanism Digital (www. mechanismdigital.com). "They look beautiful but one of the problems is it's a compressed format and this is not the greatest for greenscreen keying. It's doable, but it can be problematic. You have to make sure the greenscreen is lit very well."

Even lighting and even color temperature are very important, he continues. "Very often crews are often trying to hustle you through a stage because they're paying by the hour and don't want to light things correctly; you have to stay on top of them. They might save a couple of bucks shortening the lighting period on the set but they'll spend it in post when we're sitting there trying to fix it."

Mechanism Digital worked on 900 greenscreen shots for the History Channel special The Last Stand of the 300, the real story of the Spartans, a 90-minute special released in conjunction with the feature film 300. It was a co-production with Limulus Productions (Boston). Mechanism suggested shooting it entirely on greenscreen to mimic the approach Hollywood took. On-set the entire time, they made several time and cost-saving suggestions: shooting things with a locked-off camera and then moving it in post, shooting separate passes for more flexibility with depth of field and blurring or even replicating people in post. That was a big one since their 48 live actors needed to become 3,000 in the special. Greenscreen shots were used for the backgrounds or little greenscreen people were put in the distance to add life to the shot.

Since Mechanism artists composited, they relied on their usual prepro tests. In this instance, they use a greenscreen paper and tabletop with toy action figures and mocked up some concepts to see if they would work. Then, at the backend in post, they used Eyeon's Fusion to composite the more complicated shots and Adobe After Effects for the more straightforward ones. Hardware was custom-built PCs and Mac G5s.

Proper lighting helps solve the problem of green spill. Christopher Duddy, the DP/co-founder of Open Sky Entertainment (www. openskyent.com) in Beverly Hills, helped create a new version of the classic 1919 horror film The Cabinet of Dr. Caligari with director David Fisher, who also composited the project. They used a new technique in on-set compositing where they shot the actors completely on greenscreen and composited them into the original sets of the original film. The movie was released on DVD in June.

"We had a green cyc stage that we shot on, and those were the most challenging shots because there's a lot of green spill from the floor. We had to use an incredible amount of lighting to light the screen, the floor and the actors, and we had to overlight to dissipate the green spill on them. Green spill is really hard to composite because it bleeds through," says Duddy. "We shot the movie in July and on the wide shots we had to have every light on the stage lit, and it would get incredibly hot, like 110 degrees, and we had to turn the air conditioning off for sound."

The low budget movie ($150K) was shot in a record nine days, helped by a trick they discovered. "On greenscreen we figured out right away we didn't have to move the camera, all we had to do was flip the actors for the turnaround and change the lighting a little bit on them. Typically, when you shoot a movie scene, you shoot the master, then you go in for coverage and then you have to turn the camera around and relight," he says. Prior to the shoot, they discovered that the big old cameras used to shoot the original scenes rarely moved and always took a clean shot of the set before the actors came in. The static, clean shots made compositing that much easier, though Fisher spent a good six months doing extensive post, making the new elements look like film with filters, grain and layers in After Effects.

Duddy's extensive background with greenscreen visual effects spurred him to take on this unique film challenge. "It was very challenging and the first day was incredibly difficult because we had to line up the actors. David developed an on-set compositing situation because we didn't have the original data from the original movie, meaning camera lens angles and heights and measurements from the camera. We had to line up every shot by eye with the on-set compositing, which was extremely difficult at first but once we got into it we got into a groove with it," says Duddy. "In some of our shots, the actors touched and sat on the original sets so, for an actor to sit on a chair, we had him sit on a green apple box but we had to line it up exactly so it looked like they were sitting on a couch from the original."

Inevitably, visual effects studios do have to work with both good and bad greenscreens. Their techniques and tools are their weapons.

After focusing on good shooting and consistent lighting for the footage, Pixel Corps (www.pixelcorps.com) zeroes in on the most important part of the key — the edges, says Alex Lindsay. "Round one is to garbage out both non-green areas and poorly lit areas. Round two, for challenging keys, is to pull procedural garbage mattes and core mattes. These two processes, which are basically hard keys that are expanded or contracted to push the background to black and the foreground to white, saves 10 to 15 pixels on either side of the subject edge. This really reduces the work on the final key.

"We build many of our keys from scratch. We will occasionally use The Foundry's Keylight, but usually find we can do better on our own with 4:4:4 data and better with dvGarage dvMatte for 4:1:1 data. Typically, we use a basic color difference key and then massage the density of the matte with curves. 

Pixel Corps recently worked on a music video for Zimbabwean musician Oliver Mtukudzi that will air this summer on African music channels. They shot the band in San Francisco; the video is a completely-CG environment with greenscreened subjects. Most of the work was done with dvGarage Conduit, a nodal compositor plug-in of Final Cut Motion 3, heavily using the new 3D system. A handful of shots were done in Apple Shake, and the 3D backgrounds were created in Maxon Cinema 4D and Photoshop.

"For greenscreens, we use Composite Components' paint and screens," reports Lindsay. "For digital work, the keys provide a more pure color. We augment this with two to four 4x4 KinoFlo's. When we have enough separation between foreground and background, we've begun to use green Kinos.

"For more challenging keys, we generally rely on Apple Shake," he adds. "We use it for a variety of reasons: a) for a single multilayer file, we prefer nodal to layer-based solutions, and b) the text-based file format is extremely important for automation and sending work out since our keying work is done in the five continents, often at the same time. For DV and HDV work, we usually use dvGarage dvMatte since it's a specialized tool for this process and saves, well, a lot of time."

Ghost (www.ghost.dk), the visual effects studio in Denmark, specializes in visual effects with 3D blended into live action. Often their 3D people crossover into compositing as well. It builds up a unique knowledge of what the 2D needs from the 3D artist and vice versa, says visual effects supervisor Martin Gardeler, and it helps speed up the process immensely.

Their greenscreen techniques include using a combination of keyers. "You can use a chroma keyer to get your main key, but you can add detail in hair or shadow with a luma keyer combined with the first. It is also good to have at least two keyers at hand. Depending on the shot, one keyer can produce a much nicer key in some cases, and worse in others," he says. "We use Digital Fusion for compositing and, for keying, we use Ultrakeyer and Primatte. Sometimes we also use the master keyer or Smoke/Flint. We like the Primatte plug-in because it is simple to use and produces a good result. The Ultrakeyer is Fusion's own keyer so it doesn't require any plug-in. Who uses what is a matter of taste, but both are good options."

A recent project was Island of Lost Souls, a film that premiered in Denmark, soon to be released in Norway and Sweden. About 70 percent of its 630 VFX shots involved greenscreen, everything from green puppeteers removal to huge greenscreens for sky replacements. The plot revolves around teenagers' supernatural forces.

At Empire (www.empire-la.com), Zack Nederlander does his greenscreen work and fixes with plenty of keyers. He says greenscreen has become a giant part of the studio's business. In May they finished working on a 40-minute film adaptation of Jonna's Body: Please Hold, a one-woman play about Jonna Tamases surviving three types of cancer. The production company is looking for a distributor. Jonna was a clown, so the play and movie have a goofy feel, a la Dr. Seuss. There are set pieces around her and on her. Empire had to do all the set extensions. There are 25 minutes of greenscreen effects.

"One of the greatest tools that we used was [Red Giant] Primatte 3," says Nederlander. "It really has fantastic HDCAM decompression tools, like its 'deartifacting' option. It smoothes stuff out unlike a lot of other keyers. I have six different keyers that I use depending on what it is and sometimes you can just use a stock one, but my favorite is in Primatte 3. It's a DVCAM/HDCAM option that interprets what the image is supposed to look like. It takes away the nonsquare pixel compression." The software runs on Mac G5s though Nederlander has started doing all of his rendering on a Mac Mini, "which is kind of novel, it's so cheap." He used After Effects 6.5 to composite.

The greenscreen shoot was with standard HDCAM, with its compression issues, and at breakneck speed, a 10-day shoot with many major costume changes. The budget was $350K. "We did vendor out a majority of the greenscreen to Encore, but in a lot of cases it was so incredibly low budget that they didn't really care about quality in a lot of shots. Since they didn't know how we were treating things and how much we had to do, about 20 to 40 percent we had to fix or re-key."

Nederlander knows how to work quickly and efficiently. "I always bring a workstation and do test shots on-set. The majority of the shoots I've been doing lately have been digital, and I have a Blackmagic HD station that I bring with me so I can import the highest quality of HD into my machine, capture it and, in an offline format, bring it into Boujou, track it, key it and just make sure that it looks good."