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Filming of "Lewis & Clark" in IMAX
Director of Photography, T.C. Christensen interviewed

This article first appeared on
The 70mm Newsletter
Written by: Kurtis Burr March 2002
T.C. w/ IMAX's MSM 9801. Picture supplied by T C Christensen

For a week I had the opportunity to work, talk and travel with Director of Photography T.C. Christensen, and discuss the making of National Geographic's new "Lewis and Clark" IMAX film. This interview comprises the bulk of those conversations.

"From the start, one of my major concerns was that 90% of this film takes place on rivers." For T.C. this presented the problem of having a very similar look throughout the film. "I wanted to keep the look visually fresh so we decided to achieve this through differing the filtration." Color filtration is not usually associated with large format films. "We began the film with a Tiffen Tobacco 1 filter lending an older, desaturated and muted feel to the images. I felt this would be an effective means to pull the audience into the film through a look that they associate with viewing a historical event. For the winter sequence I used Tungsten film (5274 and 5279) and pulled the 85 filter. It is all quite bluish and cold looking." Cold during the winter segment is an understatement, much like the Corps of Discovery's experience, at one point the wind chill factor reached 30 degrees below zero, fortunately we had the advantage of fleece and hand warmers. The spring sequence was shot with normal color balance, until they reached the Great Falls of Montana. "The portage took the Corps of Discovery nearly a month and just about killed the journey. I used a Tiffen Chocolate 1 filter, which sets apart this sequence with its struggle, sweat and dirt. Everything, the beautiful skies, the cascading blue river are pushed toward a muddy, dirty brown indicating the sweat and struggle of that portage." Additionally T.C. used a Neutral Density .3 or .6 Soft Grad at the top of the frame in most shots. One of its purposes was to knock down the light level in an Omnimax theater setting that would otherwise wash out the image due to reflected light bouncing around the curved screen. He also used ND Grads to help focus the eye because "Most IMAX exteriors are composed with more headroom because the area of interest is located from the screen's center and down through the bottom one-third of frame. The Graduated filter knocks down the brightness of the sky and keeps the audiences' attention focused on the main action.
Further in 70mm reading:

The Witness Testaments

Keelboat & Pirouges. Picture supplied by T C Christensen

"One of the biggest challenges in doing an IMAX film about "Lewis and Clark" is trying to capture the incredible scenery they would have experienced almost 200 years ago. I doubt the Corps would recognize today most parts of the waterways they traveled, as it has been so modernized." Most sections of the route Lewis and Clark traveled are now a series of dams. "Many people that come to the theater will do so expecting to see great vistas with shots of these explorers set against the unexplored American west. This was difficult to achieve." One of the only areas left untouched along the Lewis and Clark trail is the Charles M. Russell National Wildlife Refuge in Montana. Unfortunately for us, there is no road access to this area, the only way in and out is by boat. "We wanted to shoot in the Refuge, but it became a question of feasibility - can we float a 32-member principal cast with a crew of over 60 and our equipment in and out each day? Do we spend a week in the Refuge? This forced the production to utilize locations that could be accessed by road. "But, if you can drive to a location there is population which means distant structures, buildings, farmhouses and power lines which are particularly troublesome for a large format film. Extensive CGI work was not an option given the budgetary constraints. It was a "Catch 22", the pristine areas were not accessible and the accessible areas were not pristine. One solution was to have Jack Tankard, who has lensed more IMAX films than most people have seen, and who was the Second Unit Director of Photography, access and shoot sections of the Lewis and Clark route in a manner that the main unit would never have been able to do.

To decide the look for National Geographic's "Lewis and Clark" IMAX, T.C. shot a test. "I went out by the Great Salt Lake and used mountains, sky, water and a model. The candidates for filtration were: Straws, Tobaccos, Chocolates and an 81C." The Director Bruce Neibaur and I watched the tests and decided that the Tobacco 1 had the best period look." T.C. also used specialized Grad filters custom made from Tiffen. "Tiffen has made me a Neutral Density .6 Hard Grad that is one-fourth ND and three fourths clear because in large format you use so many wide angle lenses. With a 40mm or 50mm lens and a standard half ND grad, you many times start to see the edges of the filter tray, you literally run out of room. The ND .6 1/4 Hard Grad is perfect in such situations." This isn't the only filter Tiffen has created for T.C.. "On many of the IMAX films I have worked on, I have wished for a way to ND the upper corners but not so much the top of the frame. One idea is to crisscross two ND Grads, one on an angle in the upper left and the other in the upper right. The disadvantage with this is that this results in a straight line and you get a double ND where they meet. Tiffen made me what I call a Half Moon Grad. This enables me to ND around a mountain peak, a person or whatever. Additionally, if the high part of the frame is left or right of center you can't move your tray left or right but you can tape the Half Moon ND onto the hard matte of the Matte Box in order to still use it." Concerning filtration with longer lenses T.C. suggests, "I've found that in IMAX if I'm using anything over 110mm at even a T5.6 that the ND filters are not selective enough, they start to ND the whole frame, or nothing at all. So what I do is take an Arri MB-14 Matte Box and tape the filter to the front of the Hard Matte which pulls the filter another four or so inches away from the lens and sharpens it up. The grips make sure there's no stray light hitting the glass hanging out there and you are ready to Grad a longer lens." T.C. will also bring the Grads in from the sides and the bottom. Specific to Grad Filters in IMAX he believes, "you can get away with heavier Grads because you really don't sit in a theater and take in the entire image at once. The viewer has to decide which part of the screen to look at. As a result you are able to work with a much thicker Grad Filter. When we project the 35mm dailies, many times the Grads seem too heavy. However, when you see it on the big screen it's not that noticeable.
Left:  DP  T.C. Christensen. Middle: 1st AC  Zep Christensen and right: 2nd AC and writer of article  Kurtis Burr. Picture supplied by T C Christensen

In 1803, the Corps of Discovery was allocated $2,500 and a letter of US credit. Our journey in 2000 cost a bit more. The hard cost involved in shooting IMAX definitely influence all large format DP's. Raw stock averages about $1.15 per foot. Running time for a 1000' roll of film is just under three minutes. The cost of a 35mm print down runs approximately 85 cents per foot. 

The viewer should notice more than a handful of uncommon shots as they watch National Geographic's "Lewis and Clark" IMAX. T.C. spoke about a few of his favorites. During the Corps of Discovery's journey up the Missouri one problem they often encountered was floating logs coming down the river and ramming their boat. These were big trees moving with the speed of the current, sometimes up to 20 mph. "So we decided the most interesting way to shoot this would be to attach the camera to a log. We found a tree floating in the Missouri, the grips attached the camera to it, and my first thought was that I would just watch the shot on video assist. Then it occurred to me that I could ride it. So I climbed up on it, hung off to the side and was able to operate." 

The night before shooting the scene where Lewis slips off a 60 foot cliff above the Missouri, the Director Bruce Neibaur, Producers Lisa Truitt and Jeff Miller along with T.C. got into a discussion on how to make this more of an IMAX event. "We got the idea to try a free fall with the camera representing Lewis' POV. We put the 40mm (very wide) on the camera and Key Grip, Matt Stelling built a go-cart contraption with four rubber wheels, then encased the camera. The go cart would then ride down the angled top section of the cliff while the grips controlled its decent with a rope and pulley system. The camera would descend approximately 60 feet. "At the same time we had the FX guys throwing rocks and dirt down the cliff along side the camera. We did three takes, the best ended up being the first where the camera flipped and rolled over on its back side." Then there was the bear sequence. "In Utah, we have had for many years Bart the Bear, who was probably the most used bear in film and television." He died shortly before preproduction began. Bart's trainer, Doug Seuss is now working a bear named Tank. "Tank is not as big, he is not as well trained, he is not as big a deal to the camera as Bart was. To help this out we came up with the idea of a bear cam. For several shots we took IMAX's Mark II which weighs well over 100 pounds, not the ideal camera for this type of shot." Over 90 % of the film was shot with IMAX's MSM 9801 which weighs just over 60 pounds fully loaded. That camera was not available for the bear sequence. T.C. continued, "The grips built a speed rail support bar to go across the top of this 100 pound camera then two of us, one on either side, would take the Mark II and with a 40mm lens run through brush and alongside the river simulating the bear's POV. I have done this type of shot before and have learned not to shoot it at 24FPS. For me it's a little too bouncy and disorienting. We didn't want to use the 30mm because of the fisheye like quality of that lens. We rolled at 28 FPS and this helped stabilize the camera movement. "There is enough movement so that it has more energy than a Steadicam shot but it is not so erratic that the audience is distracted." Another rig was created by Matt Stelling and Boat Coordinator Larry Matson. The idea was a pontoon mount that would allow the camera to float at water level. "The camera is mounted between pontoons and the lens is only about four inches above the water. I would just swing it around and get a steady moving shot in the water."

A Giraffe crane was used extensively. "It was especially good for this show because it is modular and adaptable. I could ride it by myself and get to a lens height of 24 feet. We had a remote focus system which allowed that configuration to work. If there were two of us on the crane we could go to 16 feet, and with a hothead we could reach 30 feet". There were quite a few shots which necessitated that much reach. T.C.'s preference is however, "If we don't need that much reach, I like to operate through the viewfinder. Then I can look for problems, judge contrast, exposure and focus as well as having a better chance for finding someone's water bottle that may have been left in the shot." 

Asked about choosing film stocks T.C. said, "as a rule, on an IMAX film I need a high speed tungsten and a high speed daylight. You can do anything with them. With the older EXR stocks you could tell a real difference between the low and high speeds, but 5246 and 5279 are so good that you can intermix them and not worry about it. The bulk of the film was shot on 5246, the aerials primarily tended to be 5248. The campfire scenes were 5279 and very often T.C. would push this stock one stop. T.C. rates these stocks 1/3 of a stop under what Kodak rates them, "and then of course there are other considerations such as IMAX's lenses being marked in f-stops as well as the Mark II's smaller shutter angle." These 65mm films from Kodak render these outdoor scenes with breathtaking clarity.

When asked about the films interiors T.C. smiled, "we only got to do one interior location for the whole film; Sacagawea and Charbonneau's quarters at Fort Mandan and the Captain's quarters at the Fort, which was the same set, just redressed. After having done so much daylight exterior, that was fun. 

T.C. has been told by several crew members that this was the most enjoyable film they've ever worked on. "I hope" he said, "that this film will capture the incredible efforts of Lewis and Clark and become a fitting homage to those first Americans who first explored the interior of the continent of North America."

This is T.C. Christensen's 8th large format film. His other's include, Ozarks Legend and Legacy, The Witness, Testaments and Olympic Glory.


Lewis & Clark

Producers: Lisa Truitt & Jeff Miller. Director: Bruce Neibaur. Director of Photography: T.C. Christensen. Production Designer: Andre Guimon. Writer: Mose Richards. Gaffer: Garlan Wilde. Key Grip: Matt Stelling. Assistant Camera: Zep Christensen. Music: Sam Cardon. Editor: Stephen Johnson. DP: T.C. Christensen. 1st AC: Zep Christensen. 2nd AC and writer of article: Kurtis Burr
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Updated 21-01-24