Gav with The Slow Mo Guys wanted to check out how a 16mm motion picture camera works in crisp slow motion. Using a Phantom Flex4K, he recorded at a blazing-fast 1,000 frames per second.
The Phantom Flex4K is an incredible feat of engineering and modern technology, but today the focus is on an older Russian 16mm motion picture camera. For viewers who haven’t seen how a 16mm motion camera operates, it’s neat to see the camera’s internals and how the film is loaded. With the film loaded, it’s time to set the frame rate, which is controlled via a dial on the outside of the camera. In this case, Gav will record at the standard 24 fps frame rate, although you can also record using this camera at 8, 12, 16, 32 and 48 fps.
|A close-up of the back of the 16mm motion picture camera. Here you can see the rotary disc shutter with its two cut-out sections.
Taking a step back, a digital SLR camera includes a mirror at a 45° angle to project what the lens sees into the optical viewfinder. When you press the shutter release, the mirror flips up out of the way, exposing the shutter, which then remains open for a set amount of time to expose an image. As soon as the shutter closes, the mirror flips back down, allowing you to see through the viewfinder.
|This split-view shows how the film is exposed as the disc spins on the left and what is being exposed on the right. When the mirrored disc covers the film opening, a small metal claw is inserted into the holes in the film to move it to the next frame. You can see this in incredible slow motion in the video below.
A 16mm camera operates similarly. The image coming through the lens is bounced by beam-splitting mirrors and then off a mirrored disc set at 45°. Unlike a DSLR, the 45° mirror in the motion picture camera doesn’t move out of the way to reveal a shutter but is itself the shutter. It is a rotary disc shutter. There are two openings on the disc, on either side, so for every 1/2 rotation, a single frame is exposed, which can be seen in glorious slow motion below.
When shooting still frames of Gav pouring water out using the same 1/60s exposure as the motion picture camera, Gav would exhibit some motion blur. Why doesn’t this happen with the motion picture camera? As we can see clearly at 1,000 fps, the film is being driven through the camera but is perfectly stationary when each frame is exposed, moving only when the rotary disc shutter is blocking the film. As Gav shows using a macro lens, there’s a metal claw that goes perfectly into the film’s sprocket hole to move it in perfect time with the selected frame rate. The entire mechanism is exact.
If you want to see the camera operate at 48 fps, which has a shutter speed of 1/120s, be sure to watch the full video above. You could project the film recorded at 48fps at half speed for some analog slow-motion footage.