American Cinematographer - November 2011 - 65

The president of the Swedish Society of Cinematographers, Håkan Holmberg, FSF, shows off his amateur 3-D setup, comprising two small cameras held together.

unremarked-upon during shooting for practical reasons, while others require an immediate fix. “I know we can fix vertical or horizontal misalignment easily in post, so I won’t say anything. If I see a rotation error, I will ask to fix it, because fixing it in post takes time and means a loss in resolution.” Another workshop exercise involves shooting exteriors by the icy waters near the Gothenburg ferry. Boyle has us shoot parallel using a big IA with a Stereotec rig. The shot frames the nearby water and a bridge along a stretch of coastline, from a distance of a mile or so away. We try several big IAs, including 90cm, 50 percent longer than the 65cm norm. In dailies, the resulting footage of the harbor does not look as if it was shot through the eyes of a giant, but the distant objects resemble flattened cutouts. The most convincing 3-D results are obtained with the continuous shoreline receding in the frame. “The bridge and the buildings in the distance look flattened,” Boyle comments, “but that’s how our eyes see. Our 3-D vision falls off with distance.” When watching the monitors onset, Boyle recommends taking off the 3-D glasses and getting into the habit of evaluating depth by looking at the horizontal fringes in the image. One option is to use a special 3-D-capable

monitor like the Transvideo, which offers different ways of visualizing 3-D, including a variety of helpful displays to quickly match the images on a rig and check that they are properly registered. The monitor also features helpful grids to measure the offsets in percentages or pixels. Anaglyph (the process involving bi-colored glasses) is the cheapest way to monitor 3-D on the set because the blue and red signals can be displayed on any ordinary video monitor. Watching anaglyph is tiring for the eyes, however; polarized glasses afford a far more comfortable view but require special monitors. According to Boyle, if a crew includes experienced stereographers, the filmmakers can sometimes work without any 3-D monitoring on-set to save time and eyestrain. He feels there is a danger of filmmakers growing so accustomed to 3-D that they may become desensitized to the eyestrain involved with extreme 3-D shooting. Another simple technique employed during the workshop involves using a piece of tape as a maximum divergence reference. “Our JVC monitor is about 1 meter across,” says Boyle. “Stick a 2cm red tape on the screen. That’s your 2 percent! If you’re shooting for cinema, use a piece of 1cm tape. It’s
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crude, but it works!” Time and again, Boyle emphasizes the need for speed on a lowbudget film. “You have to move fast, so directors and producers start to worry if they always see you with a calculator in your hands. I don’t want people to be aware of me doing my job. I want it all to work seemingly by magic.” As we prepare to set up shots, Boyle reminds us that we must decide where the screen position will be, and which IA to use. He notes that screen position can vary in post, but IA cannot: “It’s safest and quickest to position most objects behind the screen, and then adjust that if needed in post.” Boyle raises the issue of what he calls “Medical IA,” stating that it is sometimes important to reduce the IA in order to avoid eyestrain when shooting objects close to camera. “As objects move closer to camera, the convergence angle on the foreground increases, but so does the divergence in the background. In those cases, it’s important to reduce the IA. This will reduce the overall depth and therefore reduce both the foreground convergence and background divergence, and you won’t hurt anyone.” Boyle proposes a rule of thumb to calculate the Medical IA of a shot: the “50 Rule,” which he uses for projects
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American Cinematographer - November 2011

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