How do you capture dazzling and terrifying atomic bomb explosions on film? Blazing fast speed, that's how.
Director Christopher Nolan always focuses on finding the best camera to tell his stories. While he has been a champion of large-format film since shooting sequences of The Dark Knight on IMAX cameras, Nolan is taking a slightly different approach for his upcoming epic, Oppenheimer.
While Nolan is still using IMAX film cameras for his story about American scientist J. Robert Oppenheimer and his role in developing the atomic bomb, the director needed specific cameras to showcase the awe-striking glory and all-consuming horror of an atomic bomb exploding. The teams at Kodak and FotoKem also developed IMAX film in back-and-white for segments of the movie.
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Capturing the Atomic Devastation
Sources revealed that one of the cameras Nolan and cinematographer Hoyte Van Hoytema used was a Photo-Sonics 35mm 4C high-speed rotary prism camera, which is capable of 2,500 frames per second.
These types of cameras are not your standard fare and fill a very specific role. But this technology, which was widely used for the actual atomic bomb tests, comes with certain pitfalls that filmmakers need to watch out for.
Let's dissect this tech a bit and see what challenges Nolan and Van Hoytema needed to overcome.
Pin-Registered vs. Rotary Prism Cameras
Cinematographers today rely on two basic types of cameras for their high-speed work.
The pin-registered cameras, which are the most common of the two, have a superior image quality but have a limiting frame rate. The 16mm Photo-Sonics Actionmaster 500 is limited to a maximum frame rate of 500 fps, while the 35mm-4ER Photo-Sonics camera is limited to a max of 360 fps.
If a shot requires a faster camera, then creatives must rely on a rotary prism camera. The Photo-Sonics 16mm E10 is one such camera that can capture up to 10,000 fps while still using film, making it a great solution for slowing down motion to a near standstill.
The fastest rotary prism cameras were often used to shoot slow-motion scenes like the deployment of vehicle airbags, cereal falling through the frame, small-scale explosions, bullets exiting the barrel of a gun, and the classic water droplet and crown effect.
Outside of filmmaking, rotating prism cameras were used in high-explosive flash ("argon bomb") photography and flash X-ray photography.
How We Learned to Love the Bomb
Manhattan Project collector and physicist Clay Perkins describes one of these high-speed cameras used for the Manhattan Project and other explosive tests, the Marley camera, for Voices of the Manhattan Project as a camera "with a spinning wheel of little slots in front of a mass of individual cameras, so to speak. One piece of film, but with multiple lenses. The geometry of that allowed pictures to be taken up to 100,000 frames in one second."
And that's on film. If you run a regular film camera at that speed, you'd disintegrate the stock.
Unfortunately, the Marley camera had a fixed short focus and low-quality lenses that made it undesirable to study the explosions, so the Mack Streak Camera, a rotating mirror camera with a 0.0000001-second resolution, was used during the Trinity Test because it could provide more detail per frame for studying high-speed events.
This speed made it possible to study the atomic bomb.
Rotary prism camera technology has advanced greatly, yet it is rarely used in filmmaking for the ultra-slow motion moments like we sometimes saw in Nolan's mind-bending Inception.
When it comes to bombs, they usually go off too fast to see the explosion. For a movie about atomic bombs shot on film, Nolan and Van Hoytema needed a camera that was capable of capturing the devastating and Earth-shaking effect.
How Does the Rotary Prism Camera Work?
Rotary prism cameras can be fickle hardware that require a bit of special attention and a delicate touch. When compared to standard-speed tools, DPs have to deal with several issues to get the best possible image.
Unlike conventional film cameras, high-speed cameras do not use intermittent movement to advance the film. Instead, the continuous movement of a prism in place of a normal camera shutter allows the film to move at a higher velocity than with intermittent movement.
The rotary prism 4C camera’s imaging technique has a “wiping effect,” where two parallel surfaces exist in a piece of optical glass (the prism), and light rays enter the first surface and, by refraction, follow a shorter path through the glass. The light rays then leave the prism’s second parallel surface at the angle that they first entered.
As the prism rotates, it moves the image in sync with the film. Because the four-sided prism and the film are constantly in motion, the relative motion between the image and the film during the exposure phase is zero. This is an effect of the wiping effect and having no hard aperture plate. One frame blends into the next without showing a sharp frame line.
Things like reciprocity can become a critical failure point in the workflow. This is the inverse relationship between the intensity and duration of light that determines the reaction of light-sensitive material. Because film is less responsive at very low light levels, reciprocity failures are common with high-speed cameras since the frame rate is so high. The faster your film speeds through the camera, the less light it can capture. To combat this, Photo-Sonics recommends that DPs using the rotary prism camera open up the exposure to 2/3 to 1-1/2 stops, depending on the subject.
This also creates a very narrow depth of field, which can be a challenge when attempting to have a repeatable focus on set, which is why seasoned DPs need experienced focus-pullers when working with these particular cameras.
The Disadvantages of a Rotary Prism Camera
Not every camera is perfect, and rotary prism cameras have one noticeable flaw.
The camera produces a slight bit of image bounce and side weaves while capturing the shot. While this bounce and weaving are unnoticeable to untrained eyes, there is a slightly noticeable effect happening in the camera when there is a point of registration in the frame.
Let us explain.
If you are shooting a drop of water falling into a still pond with a rotary prism camera, then the viewer will be able to notice the image bounce when the still water is changed the moment the water droplet hits the pond. The motion reveals that the image is not rock-steady. This means that most of the shots need to capture moments that are already in motion.
I assume that Nolan used the rotary prism camera to capture the explosion effects in Oppenheimer, and this flaw doesn't affect Nolan's workflow. Explosions don’t really need to consider this flaw with the camera since the jumpiness of the camera serves as the visual violence of an explosion. Flying parts and debris make up a majority of the frame, so there is little in the frame that could be used as a reference to camera registration.
The Wait Begins
Unfortunately, we won’t be able to see the glory of the Photo-Sonics 35mm 4C high-speed film camera until July 2023. We will keep our eyes open and ears close to the ground for any details surrounding the massive and inventive production behind Oppenheimer.
We're looking forward to each trailer that comes out since we will be looking for those massive explosion shots captured on film.