FCP X: Variable Speed Effect
I’ve written earlier about how to create still frames in Final Cut Pro X. In this article, I want to talk about how to apply a variable speed change to a clip.
Here, FCP X takes a different approach to variable speed than FCP 7, in that it changes the speed of a clip in steps, rather than with a smooth curve.
Here’s how this works. (Thanks, by the way, to Standard Films – www.standardfilms.com – for permission to use this clip.)
Here’s a clip of a snowboarder sliding down hill. (It is, um, about 800 degrees in LA as I write this – so all this snow looks REALLY nice!)
I want to slow it down as he gets engulfed by the snow, then speed it up at the end. The key tool that makes this happen is the Range Selection tool (R).
Select the Range tool from the Tool menu, or type R.
Drag a range inside the clip that starts where you want the speed change to start and ends where you want the first part of the speed change to end. In this case, I want the beginning of the clip to run at normal speed, then slow down as the plume of snow grows behind him.
Go to the Retime menu – it looks like a Smurf on a headset – and select Speed Ramp > to 0%. This creates a gradual slowdown of the clip – in four segments – over the duration of the selected range.
Several things happen at once: the Retiming Editor is displayed above the clip, and the selected range is divided into four speed segments – 87%, 63%, 37% and 13%.
When you play the clip, it starts a normal speed and gradually slows down, until it touches a single freeze frame at the end of the ramp; indicated by the red “slice” at the end of the range.
Using the Range Selection tool, select the second portion of the clip. In this case, I want to have the rest of the clip increase in speed until it is going faster than normal at the end.
Go back to the Retime menu and select Speed Ramp > from 0%. This creates a gradual speed up of the clip over the duration of the selected range.
AVOIDING THE FREEZE FRAME
If all you want to do is change the speed of a clip in sections, but not slow it all the way to zero, use the Range Selection tool to select a series of ranges in the clip and apply a constant speed change to each range. Then, adjust to suit.
ADJUSTING THE CHANGES
To adjust any of the speeds of any of the segments, grab the small thumb at the right edge of each orange bar and drag left or right. In this case, I changed the speed of both segments around the still frame to run at 20%, rather than the default 13%.
To change the frame where the speed ramp changes, click the downward pointing arrow next to the speed listing and select Change End Source Frame. Drag this left or right to change the frame where the speed changes.
NOTE: Don’t change the position of the freeze frame, as this can cause major problems with the speed of the entire clip.
For the ending of this shot, I changed the speed of the last three segments – by dragging the thumb – to 61%, 100%; then clicked the small downward pointing arrow and selected Fast > 2x to change the speed to 200%.
So, the final effect is the snowboarder flies in, slows down as he kicks up a massive plume of snow, then speeds off into the distance.
When done, hide the Retiming Editor by typing: Command+R.
This looks very cool!
NOTE: If you will be slowing clips below about 30%, switch the video quality to Frame Blending. If you are going slower than about 10%, switch the video quality to Optical Flow. Both will improve playback image quality at slow speeds, though Optical Flow will take a while to analyze the clip.
RESETTING A CLIP TO NORMAL
If you need to reset the speed of a clip to 100% normal speed, select the entire clip, and either select Normal 100% from the Retime menu or type Shift+N. The clip returns to normal speed.