Basic slow-motion (or high-speed video)

Split-second events recorded at high frame rates produce some of the most beautiful images we don’t normally get to see.

If we want to record slow motion in high definition video, the first step is to select a camera that is capable of shooting variable frames rates, like a Phantom Flex, ALEXA or RED. However, lowbudegt filmmakers arent left out with new and approved technology. At an afforable cost, mirrorless and DLSRS cameras such as the Sony A7 series, Cannon C500, and Blackmagic URSA can get a job well done. When we record at high-speeds from 60, 120, to over 2,000 fps, we now have the ability to slow down the footage and see the subject playback in slow motion. The elements you need to record at high speed include an abundance of light, access to a prime lens kit, a good fluid head tripod and a high speed digital camera.

Our goal is to balance the shutter speed and frame-rate so that we record enough crisp images to create smooth slow motion in playback at 24 fps. We want to avoid stuttered motion.

Do you understand how the F-stop works? It determines how far open or closed the aperture on your camera will be. To be clear, high F-stop numbers like F10 – F 22 will close and narrow the iris to allow small amounts of light inside the camera. In contrast, low F-stop numbers like F2 – F5 will open the iris wide to let more light.

Moving on, the shutter speed determines the speed at which the shutter opens and closes. The faster you set the shutter speed the crisper the video will be. The slower you set the shutter speed the more choppy the motion will be. This can come in handy when deciding what type of feel you want your video to have.

In addition, the frame rate determines the number of still images that are created in that video. Typically we stem together 24 images in one second to create motion (24fps). In each second we see 24 individual frames. If we increase the number of individual frames we want to capture per second, say from 24fps up to 60 fps or 120 fps, we can speed or slow down the content in post.

To create slow motion, first, set your camera to record at 60fps, set your shutter to 1/120 and record your scene. Next, import the 60 fps footage into a Premiere timeline and set the sequence to 24fps. Use the speed controls in Premiere to set your slow motion speed to 50%. This is one way to record slow motion.  When you capture a subject at 120 fps and play back at 24 fps, the motion will appear at 1/5th speed.

Here are the golden rules when it comes to slow-motion video; always make sure to double your shutter speed to whatever your frame rate is. For example, if you shoot at 60 fps set your shutter speed to 1/120th of a second (the higher the shutter speed typically the more light you will need).

Overall, understanding high-speed videography may be confusing at first, but it can come in handy when trying to slow down motion in post production to create some interesting images. In order to get an object slower on the screen we must increase how many frames we shoot per second. To learn more behind the physics of slow motion, check out;

RED DIGITAL CINEMA http://www.red.com/learn/red-101/slow-motion-video

http://io9.gizmodo.com/5849356/high-speed-video-reveals-the-bizarre-physics-of-an-ordinary-water-droplet

http://io9.gizmodo.com/5920952/high-speed-video-reveals-the-bizarre-physics-of-slinkys

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