what is it?
‘motion detect’ is an iMovie plug-in that highlights motion in your clips. it does this by comparing to successive frames, and high-lighting differences between those frames. the plug has additional controls to amplify changes, and to suppress very small changes. it can also super-impose the original frame over the changes.
what should I use it for?
this is a highly specialized plug-in, originally developed for the scientific crowd , but the resulting effect looks nice (if strange) for the rest of us. use it whenever
- you need a cool-looking moving outline
- need to highlight changes (e.g. in time-compressed clips)
area of effect
the contents of this rectangle will be affected by the plug. to resize the rectangle, click and drag into the handles. to move it, click and drag inside the rectangle.
clicking this button will select the whole surface of the clip. in the context of this plug this will mean that the clip will not be changed.
this slider controls how sensitive the motion detector will be. changes below this threshold will be ignored. this is very useful if you want to suppress a background that is in constant slight motion (leaves on a tree, water flowing, steam rising, etc.)
since the motion detector shows motion by their difference to the previous change, small changes become very dim. you can choose to amplify changes. the resulting picture may become grainy though amplification. amplification is a post-processor that only works on changes that have been detected. therefore, you don’t have to adjust sensitivity after you have changed aplification.
you can choose to have the result super-imposed on the original clip. usually, parts of the clip that don’t contain motion are black, while motion is high-lit according to the rate of change. if you combine this with the original clip, those parts of the clip that have motion become brighter.
sometimes you have original footage that was shot at a different fps than that of DV (which iMovie puts at 30 fps). upon conversion to iMovie, additional identical frames will be inserted. this will seriously impede the motion detector, since added frames do not show any motion. to avoid this, you can set the frame interval. if you set it to 1 (default), the plug assumes that every frame is unique. if your clip consists of pairs of identical frames (because it was shot at 15 fps), use 2. this plug supports footage that contains up to 5 identical frames (was shot at 6 fps).
all contents © 2003-2010 by cf/x