The retiming tool is handy in Final Cut Pro X (FCPX) for slowing video motion. One of the challenges we found is adjusting the shutter speed to get the best result from slow motion. FCPX has three different video quality options for retiming, or slow motion. There are Normal, Frame Blending, or Optical Flow. As expected, as the quality selection is increased, the rendering time increases. The increase in quality is well worth, as you can see a definite difference in the increase in quality.
The test examines the difference between 1/60th second versus 1/2000th of a second shutter speed on a Canon M-500 using the highest quality AVHCD at 24MB/s, adjusting video speed to 25% of original. One thing we found is the real high frame rate shots do not blend well when the object moving through the frame has a hard edge, like the back end of a mini van. Once the van is relatively small in the frame, the blending improves markedly. As seen in other video slowdown programs (Twixtor), hard edges do not seem to blend as well, as they’re very apparent.
We made this evaluation to see if the quality improvement with Twixtor might be worth it. But, we found that because the camera we are shooting potential shots with uses AVHCD, which does not handle strong motion well in the first place, getting a clean slow motion is troublesome. Also, we edited this video on a Macbook Pro Retina (MBPr) and found the AVHCD video on the screen just does not look good compared to outputting the video to the HDMI port to a regular HD 1080 television.