So what is variable frame rate?
Variable Frame Rate, or VFR as it’s more commonly known, or Varispeed on some high-end professional cameras, is a term widely used in the film industry for shooting at a different frame rate than your record/clip delay to achieve either slow motion or speed boost in camera.
So, in short, VFR, is a way to record internal slow motion or ramp up (speed up) in your camera, and without having to work the video editing magic later on during editing. The number of frames per second you can record in VFR mode and in which codec is limited from camera to camera, so your mileage may vary. However, it’s more common these days to see cameras recording VFR at at least 120 fps or higher on higher end models.
Suppose you want to record a time-lapse through a cityscape with your video camera. You’ve set a project for a 30 fps timeline for your recordings, but you want that final time frame to show up very quickly in your final project. Using a variable frame rate and recording at, say, 15 frames per second means your camera will record half the frames you need to meet that 30 fps requirement. So when you play that footage in the camera or on your computer, the footage will play at twice the speed you shot it.
So a 10-second recording shot at 15fps on a 30fps timeline will actually be five seconds of footage, producing instant hassle-free speed mapping that requires no technical knowledge of your video editing software. It’s a pure recording, drag-and-drop option that makes editing video later a less stressful experience.
To better understand frame rates and variable frame rates, watch this informative video from B&H that shows the true power of VFR and how you can use it in your next project to create captivating visuals:
This VFR effect/option can also be used for slow motion, but rather than your recording being twice the speed you filmed it at, it naturally becomes twice as slow. If you want to film a water balloon bursting in slow motion, you can set your camera to record a VFR clip at twice the frame rate of your project, creating 2x slow-motion playback in the camera instead. than having to try to calculate frame rates and speed adjustments in a video editor.
It should be noted that VFR is not implemented on all cameras capable of shooting video, but is more commonly found on cinema cameras or prosumer cameras geared towards a “video-first” approach. We can also say that these effects can be achieved in the editing studio; however, when you start looking at your post-production editing options, they’re sorely lacking compared to in-camera VFR production.
So why not get out there and see what you can capture? You might even surprise yourself how easy and relaxed the VFR experience is, and it might even be your preferred method in the future.
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