perform an IIR blur filter on a stack of frames from a movie using imagemagick and ffmpeg

iirMovie.sh

#!/bin/bash

# ffmpeg -i movie.mov -r 1 fooframes/frames%05d.jpg
# extract 1 frame for every second of the movie...

mkdir IIRframes;

let "frames=4243/2"
echo $frames
cp WSPC0001.JPG IIRframes/new.jpg
cd IIRframes
cp new.jpg middle.jpg
cp new.jpg last.jpg
	counter=100000
	c2=100000
	for f in ../WSPC*.JPG; do	
	let "counter+=1"
	let "c2+=1"
	composite -blend 15 $f last.jpg -matte blend.jpg
	cp blend.jpg outframe${counter:1}.jpg	
		cp blend.jpg last.jpg
		
#	montage -geometry 480x360 ${DA}/$A$foo.jpg ${DA}/$A${foo2}.jpg ${DA}/$A${foo3}.jpg ${DA}/$A${foo4}.jpg ${WDIR}/4panel${counter:1}.jpg  
		echo $counter
		done
		
pwd
ffmpeg -i outframe%5d.jpg -qscale 6 IIRfarm.mp4

What does this do exactly? Is this good for aligning several photos to make a time lapse?