Slow motion app for macbook?

Shooting a slow motion video! I have a basic Nikon camera to shoot with and a Macbook. What is the best editing app to convert a regular speed video to slow motion? I want it to look really clear and crisp, but don't want to spend too much money either (nothing over $200).

You shoot slow motion video with a good camera that can take slow motion. With a regular speed video you will get blurring and artefacts if you convert it to slow motion as there's not enough information captured in the video for it to look really clear and crisp. Start with iMovie and see how that looks…

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This was shot at 240 frames per second (which is the minimum you would want from a camera) on an iPhone…