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Making Sahara Glow

Apr 1, 2005 12:00 PM, By Michael Goldman

Mastering Light with a New Filter and a Delicate DI

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Digital Solar Reflections

Paramount's Sahara, directed by Breck Eisner and starring Matthew McConaughey, is an old-fashioned adventure thriller in which heroic characters, lost and desperate under a brutal desert sun, manage to maintain a charming sense of humor. Even in their most dire straits, however, those characters seem to have it easier than the crew did while shooting key sequences in the Moroccan desert last year. (The film's primary location shoot took place in Erfoud, Morocco, in the heart of the Sahara near the Algerian border, in addition to stints in southern Spain and on stages at London's Shepperton Studios.)

According to DP Seamus McGarvey, BSC, the 12-week Morocco shoot became “quite biblical” at times. “We experienced swarms of locusts,” he says, “not to mention flash floods and dozens of sandstorms.”

On top of those incidents was a constant, beating sun that impacted not only the shoot, but also the movie's look, according to McGarvey. The DP and Eisner wanted to take advantage on film of what McGarvey calls the desert's “harsh sunlight with azure blue skies and high reflectivity off a bleached earth.” But he adds that filmmakers had to wrestle to make sure the sunlight worked for them and not against them.

Sahara Gold

In Morocco, McGarvey used a combination of three Kodak Vision stocks — 5248 for most daylight exteriors, 5274 for exteriors in overcast situations, and 5218 for nighttime exteriors. Given conditions in the desert, though, he had his hands full producing a negative that colorist Adam Inglis at Framestore-CFC, London, could later maximize during the digital intermediate phase. McGarvey says the eventual look of the desert sequences evolved out of location scouting and extensive tests about the quality of the desert light.

“Soon after I was hired, we went to scout in Morocco, and I took a lot of still photos, just to familiarize myself with the quality of the harsh sunlight there, and I quickly realized there would be lots of challenges,” McGarvey says. “What I realized prior to shooting on location [with three Panaflex Millennium XL and two Arri 435ES film cameras, outfitted with Primo lenses] was that I would need a lot of filters, so on my initial technical scout, I got Panavision in London to give me an 812 warming filter, a sepia filter, a polarizer, a neutral density filter, a diffusion filter, and others. As I tried them out individually and in various combinations, I quickly realized that what I really needed was a combination of those various filters. I approached [New York's] Schneider Optics with the idea of asking them to combine these filters into a special filter for me. They produced one that I called ‘Sahara Gold,’ and we had so much success with it that they are now marketing it under that name.”

According to McGarvey, the Sahara Gold filter was used extensively during exterior work in Morocco to enhance skin tones and to add vibrancy and warmth to a fairly bleached-out environment. “We wanted to give the movie a warm quality overall,” he says. “We wanted a classic feel to the action sequences in the desert, in terms of the way we shot it. Sequences shot in morning light benefited from the filter the most. There was a lot of blue ambiance from the skies and shadows that would go toward deep blue hues during those periods. The filter gave us a warm wash or a golden patina over those images. That helped even out the discrepancy between those cool blue areas and the warmer highlights. It was really good for blending disparate tones. It also made things cleaner for the DI, and it helped unify our second-unit imagery with the first-unit imagery.”

The filter was also used during a sandstorm, when Eisner and McGarvey opted to keep cameras rolling. “The results were beautiful,” McGarvey says. “There is a unique quality of light in a sandstorm that creates coral diffusion and atmosphere. During that stretch, it was a real credit to our focus pullers, the first assistants, and our whole camera crew to shoot that stuff without getting a single scratch on the film.”

McGarvey adds that there was no particular trick used to protect the camera equipment from the desert during the shoot. Rather, the crew made a concerted effort to combine its extensive experience in such environments with a fanatical maintenance schedule.

“Our ‘A’ camera first AC Carlos De Carvalho had lots of experience shooting in Namibia, South Africa, and other desert locations, and he really knew how to deal with sand,” says McGarvey. “As he suggested, we did not bag the cameras. We let the wind blow over them, with nature doing the job of blowing any accumulated sand off the camera as we filmed. That let us operate naturally, although there was a lot of buildup of sand by the end of the day. But our technician, Steve Wills of Panavision, stayed up all night servicing the gear. We smartly planned ahead of time that we would need a technician for the entire shoot. We had three cameras in the first unit and three in the second unit, so he would clean and service and lubricate them and make sure all movements were OK. That saved us from real disasters in terms of scratching. The technician was definitely worth the investment.”

The look of the imagery filmed under such extreme conditions and harsh sunlight also had another consequence — it caused Eisner and McGarvey to change their dailies approach in Morocco. Filmmakers started out attempting to view HD dailies on a big screen through an HD projector at their Morocco hotel, but they ended up switching to film dailies early in the process, screened through an Arri LocPro portable film projection system.

“We brought a digital projector to Morocco with the idea that we could see HD dailies quicker,” McGarvey recalls. “It was quicker, but it was impossible for us to gauge the look of the show in the extreme conditions in HD. The light was just too harsh, and the HD transfer and projection did not have the range we needed. It looked all blown out, with no detail in the highlights — it looked like video. That was disappointing, but with this kind of show under these conditions, it just wasn't the best choice. Fortunately, I had previously negotiated for a handful of selects to be transferred to film during the first two weeks of the shoot. I therefore brought an Arri LocPro to screen those selects each night before the director watched all the rushes in HD. Breck agreed with me about the HD rushes, and so, we just started watching the film selects exclusively. Our production sound mixer [Chris Munro] found an [FTP-based Internet approach] that permitted him to download a CD of sound rushes and synch them up to film selects easily, so we just watched film dailies for the rest of the production. That let us view the high-contrast environment accurately, and we knew where we were going with color. It made a huge difference in tracking the look of the film during production.”

Munro explains that his solution was based on the fact that the film's editorial work was being performed in London, where sound and picture were matched up in the Avid, while mute film dailies were simultaneously being sent onward to Morocco to give filmmakers the fastest look possible at the imagery. “We set up an FTP site for the audio so that the editors could upload the audio after synching,” Munro says, “and we could download to a CD on location. That way the audio composition was ready by the time the dailies arrived on location.”

Then, to synch picture and sound on location, filmmakers slaved a Fostex DV40 DVD-RAM master recorder by timecode to the Arri LocPro projector — running the recorder in synch with the projector during dailies sessions. “We prefer to use the DV40, rather than DAT or DA88, mainly because it doesn't require realtime playouts from the Avid dragged and dropped to a CD and also because it locks well to the LocPro,” Munro says. “This allows high-speed viewing and the ability to rock-and-roll, so to speak, to allow the director to quickly view or review takes that he is particularly interested in. We were able to similarly slave the DV40 to an HD player when we were doing HD dailies.”

The DI

Colorist Adam Inglis insists McGarvey's painstaking efforts during the location shoot were central to finalizing the film's color palette during the DI. “Seamus shot a great-looking negative through the Sahara Gold filter,” he says. “That warmed up the shadows and gave us a very good starting point.”

That negative then came to Framestore-CFC, where it was scanned on a Northlight scanner before conform editor Mike Morrison put together the final version of the movie using a Baselight (v. 2.0.687) software-based color correction system, viewing the imagery on a 24in. Sony FW-900 wide-screen monitor. (At press time, Frame-store-CFC had begun using JVC HD-2K D-ILA projectors in DI suites, but those systems were not up and running during Sahara's time at the facility.)

“Baselight is the entire conforming tool in our system,” Inglis explains. “Mike loads in the Avid EDL [from offline editor Andrew MacRitchie], and it automatically conforms the scans that come out of the Northlight scanner, which have keycode embedded in them. He then goes through the whole thing, checking accuracy against the offline version and adds any opticals. He does this in the same software that I use for color correction.”

McGarvey, who was working on his first feature DI, insists the looming DI process did not radically alter his shooting approach in Morocco, or elsewhere, during production. It did, however, satisfy him that disparate elements could be seamlessly matched later on.

“I knew going in that I could affect contrast overall on a scene during the DI, and that was helpful because I could increase contrast to the wider picture, knowing we could reduce contrast for a more pragmatic effect on faces specifically in the same shot,” says McGarvey. “We did that a lot, for instance, in close shots of Penelope Cruz. The process also paid off for material shot when we did pickups back at location, or when we were matching first- and second-unit material together. We did a pretty good job matching in-camera, but inevitably, there were scenes from Morocco that had to be cut together with things from Spain — shots that were meant to be the same place in the movie. The quality of light, color contrast, and so on were all things that we knew we could affect and improve in terms of matchability during the DI.

“Knowledge of the DI helped me more in that sense than in terms of any specific shortcuts for lighting or whatever to save time. I never said, ‘I won't cut that light because I know I can cut it during the DI.’ We shot it as a normal film, with knowledge of how the DI could help us match everything later. Having said that, we did many subtle things during the DI that would not be possible in a normal film laboratory. In particular, matching skies, or if we had reverses, with the shot going one way and being backlit and the sky going the opposite direction. There was a lot more chroma in the sky, and it was bumping visually. In the DI, I could brighten out the blue sky a bit more, and that, in the end, produced a nice effect.”

Inglis agrees that this issue of matching elements was crucial during the DI process. “With much of the material shot at different times of day in the desert, some of the sunlight was flat, and some of it was brighter,” he says. “Baselight has powerful secondary color correction tools to add shadows and sunlight to shots, working with contrast levels and other things. For example, in sequences like the big boat chase in this movie, we had to key out the water and make the skies all match up. That was one of the hardest things to do.”

The DI left another key impression during the film's opening sequence, featuring a Civil War-era attack on a Confederate ironclad ship, which sets up a key plot element. That was the one part of the movie that required a significant departure from the rest of the film's look.

Inglis says that the notion during the Civil War scene was initially to desaturate almost everything and then bring color back into the explosions and gunshots. “For story-telling purposes,” he says, “we needed to establish a far different look for this scene from the rest of the movie. We could have done some of that photochemically, but the thing is, with the DI, we were able to try so many different things, to experiment in order to get what the filmmakers wanted. Most productions can't afford to spend many weeks sending tests back and forth to the lab. With the DI, we were able to efficiently test different things.”

Inglis adds that Framestore-CFC's experience as a visual effects provider gave the company invaluable experience in terms of establishing an effective procedural pipeline for the project, enabling close coordination with Cinesite London (see “Digital Solar Reflections,” page 30) and other vendors to track visual effects shots.

“Mike Morrison and our DI producer at Framestore, Marcus Alexander, did a great job keeping track of which elements were the right elements and keeping the conform up to date,” he says. “There were so many visual effects shots in this film [380] that blending them all seamlessly using a traditional photo-chemical process would have been very tricky.”

Alexander explains the system his team employed to track effects shots on Sahara as a fairly simple but carefully controlled approach to the problem. “Firstly, we need to agree with the effects facilities on a standardized naming convention at the point of supply, which must echo the naming on the effects locator in the cut list,” he says. “We also need to agree with the production as to whether we require temps to grade. This is dependent on timescale, grade complexity of the effects sequences, and the preferences of the client. On Sahara, we used final shots most of the time and sometimes received alternate final versions for Breck to approve during the grading process. Then, we use a fairly simple but carefully controlled method of tracking shots — cross-referencing an effects list from the production with a spreadsheet I create detailing all effects files supplied to date, including the version number, the active frames in the cut, which reel they fit into, and whether it's a temp or final. Provided these lists are maintained with vigilance, particularly if the cut changes, we thus have all the information available to manage the data, the conform, and the delivery status of shots.”

At press time, McGarvey was shooting Charlotte's Web in Australia, and he says that his DI experience on Sahara had a “major impact” on his entire shooting plan for that movie, which was expected to undergo a DI later this year at Efilm, Los Angeles. “I understand the process better now,” he says. “Because of my work on Sahara, I know what lies ahead of me, and I'm therefore better equipped to apply the possibilities during the shooting stage more on this project.”

---

Digital Solar Reflections

Among Sahara's 380 visual effects shots and a plethora of practical effects, explosions, crashes, and stunts is the film's centerpiece effect — a mysterious solar plant in the middle of the desert, consisting of a 350ft.-high tower surrounded by 8,000 reflecting mirrors. The tower, the mirrors, and surrounding environment involved hundreds of digital and practical elements stitched together at Cinesite, London, following a “huge R&D effort,” according to Mara Bryan, the film's visual effects supervisor.

“The solar plant environment is key to the entire plot, and obviously, most of it didn't exist,” Bryan explains. “Our art department built two tiny fractions of the tower structure in Morocco, and the rest of it had to be created in CG and compositing, but it had to appear photo-real in full desert sunshine in order to work.”

(Cinesite's work on the sequence built upon a digital previsualization scheme created for the production in Maya by Fuzzygoat, London, which also did extensive previz for other portions of the film. London's Double Negative was the other primary visual effects vendor on the project, and accounted for the digital parts of the opening Civil War battle sequence.)

Filmmakers built two small pieces of a giant solar tower, central to the film’s plot, in the Moroccan desert. Cinesite, London, created the rest of the structure, surrounding mirrors, reflections, and environment using digital techniques.

According to Bryan, the solar plant was based somewhat on actual structures, but with a much taller tower and many more mirrors. The need to create photo-real reflections in 8,000 mirrors, she adds, involved a great deal of ingenuity from Cinesite's 3D team.

“You don't get a realistic feeling of reflectivity in each mirror unless there is some kind of camera movement,” she says, “so we would add movement to new shots and then go back and add it to earlier shots. We kept building it until it just looked right to all of us. When the mirrors were all in the same position, it didn't seem quite as believable as when they were in different positions, so we learned a few tricks along the way to address that. One of the tricks was to cheat the color of the reflections and to play around with the level of dust reflected in the mirrors. That way, when the camera is close to them, you get a texture, a pattern. We also realized the reflection would saturate the image that was being reflected, so we learned to vary it somewhat for each mirror. Some of those shots are not scientifically realistic, but they looked great and gave this impression of randomness and camera movement to the reflections. [Cinesite] built a proprietary randomization program for the mirrors, but then, at times, some of them looked too random, and you couldn't focus on any of the objects being reflected. So, at that point, we moved back and tweaked it until it looked right.”

Royston Willcocks, Cinesite CG supervisor, explains that Cinesite's basic technique was to initially build a single CG solar panel in Maya (v. 5.0.1) that replicated the handful of practical panels built for the location shoot. “Then, we digitally copied it 8,000 times, and randomness was created largely through position and orientation of objects in the mirrors,” he says. “We wrote procedural animation scripts for the mirrors, and then we varied textures and ground details as needed by hand. As a consequence of the reflective elements in the scenes, each render through Renderman was highly memory-intensive. This part of the project initially tested our render farm, but fortunately, our guys did a great job optimizing it before the project ramped up.”

Still, animating the mirrors and their reflections was only part of the battle. That imagery still had to be combined by the 2D team, headed up by 2D supervisor David Sewell, with live-action plates and environmental plates. Bryan captured many of those plates herself from a helicopter in Morocco, using a Wescam gyro-stabilized aerial camera mount.

“The tower was supposed to be 350ft., so I spent a lot of time in a helicopter at 350ft. gathering plates and also shooting still photos on film for environmental mattes,” she says. “We shot with the same film stock as the main unit and did lots of things with a cameraman hanging out of the helicopter on a monkey strap [harness]. The Wescam was very helpful for this kind of work because it captures a smooth pan and a 360-degree environment easily when shooting from a helicopter. There are lots of moving shots showing the solar plant from above, and the Wescam footage and 35mm stills allowed us to create our own environment. Eventually, we turned that into a rendered CG matte painting, which was used extensively in the movie.”

Using Shake (v. 3.51), Sewell's 2D team stitched together the plates to create a virtual 360-degree desert environment for importation into Maya. They then carefully integrated live action with enhanced lighting effects inside this virtual environment.

“We spent a lot of time figuring out the best way of subtly incorporating heat and light components to finish off the illusion,” says Sewell. “We had to emphasize what the solar plant actually does — it reflects heat and light. The mirrors gave us a second, huge light source in a strong sunlight setting, so we had to do a lot of research into that to figure out ways to make the footage look bright, glaring, and dangerous. We used a lot of real shot footage of lens flares, along with creating our own digital plug-ins of heat haze and lens flares. This gave the light a disturbing look that interacts with the actors while they fight on a platform at the top of the tower.”
— M.G.

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