The phrase “in the blink of an eye” also applies to the lens. About 24 or 25 Frames Per Second (fps) are captured with an HD video frame. Due to incredible speeds, visual processors in our brains interpret this succession of images as a single movement.
Variable frame rates (VFR) provide more control in situations with faster frame rates after slowing rates down to 24 or 25 recorded frames.
Most HD video cameras feature a VFR setting. The most basic are coupled with a PAL and NTSC switch that provides a range of 24 fps, 25 fps to 30 fps at both 1080 and 720 frame sizes.
Modern DSLRs provide a slow-motion range of 50 fps in PAL mode and 60 fps in NTSC mode for 720 frame sizes. The highest-end digital cinema cameras support hundreds of fps, while specialist high-speed cameras run at tens of thousands of fps. The higher the frame rate, the more detailed a slow-motion video can be.
Hit the brakes
To add drama into action or fight scenes, consider slow motion filming. Also called “overcranking,” it emphasizes the intense portions of a scene.
When filming on unstable platforms, smooth out the footage by capturing more frames. More frames show a lower rate of change of scene detail, which deliver a stream of action with minimal interruption. However, as each frame exposes for a shorter time, more light is needed for high-speed filming to expose all frames properly.
While shooting at high frame rates is termed “overcranking,” shooting videos at lower frame rates is called “undercranking.” Lower frame rates allow more action to happen between frames – useful for slow-moving scenes that echo time-lapse footage.
Instead of taking a single frame once every two seconds, light is spread across frames to leave light trails for a dreamy look. Imagine busy traffic with speeding cars and streams of light trailing close behind. Frame rates here range from 1 to 3 fps. This situation allows for easier low-light techniques, as less light is required between frame.