How to Convert from a Higher to a Lower FPS Rate
Video’s real time playback speed is usually 30 fps (it’s really 29.97 fps and some cameras play back at 24fps). Changing the recording frame rate of the camera has the ability to create high speed and slow motion effects. These effects can also be achieved in post-production as well. Now, these are technically special effects so they need to be properly executed in order for it to work smoothly without errors. Here’s how you can properly convert from a higher to a lower fps rate.
Step 1: Converting in Camera
Some cameras offer the ability to adjust the recording frame rate. If you were to lower the frame rate from 30fps to 15fps, then you will have video with the high speed effect when played back.
All cameras are different. Not all of them allow you the ability to change the frame rate, and the ones that do all have different ways of accessing the feature in the camera’s menu. But, one factor of frame rate conversion that is universal is that the aperture needs to be adjusted to compensate for the altered shutter speed.
When you lower the frame rate, then you’re slowing down the shutter speed which means that the image is exposed for longer then 1/60th of a second. You need to compensate by closing the aperture to the appropriate f-stop, or else your video will suffer from over exposure. If closing the aperture is not an option, then you either have to add ND filters to the camera or physically find a way to reduce the actual lighting.
Step 2: Converting in Post Production
You can also easily lower the frame rate after the fact in post production without sacrificing the video’s quality. This is done by taking frames away from the clip. If you remove every other frame from a ten second clip, then it will appear to playback faster at a duration of five seconds.
Now, you don’t need to actually go through the program and do this tedious work. Most editing programs have an option that allows you to quickly convert the speed of a clip with the click of a button. This allows you to make changes quickly while being able to see the results instantly. The best part about altering the frame rate in post is that if you don’t like what you’ve done, you can just undo it to start over, whereas changing the frame rate in camera means that you have to work with what you’ve done.