How to write every Nth file to new folder - bash

Question

I have this code which scans folders and moves all files in each folder to a new one.
How do I make it so only every Nth file is moved?
#!/bin/bash
# Save this file in the directory containing the folders (bb in this case)
# Then to run it, type:
# ./rencp.sh
# The first output frame number
let "frame=1"
# this is where files will go. A new directory will be created if it doesn't exist
outFolder="collected"
# print info every so many files.
feedbackFreq=250
# prefix for new files
namePrefix="ben_timelapse"
#new extension (uppercase is so ugly)
ext="jpg"
# this will make sure we only get files from camera directories
srcPattern="ND850"
mkdir -p $outFolder
for f in *${srcPattern}/*
do
mv $f `printf "$outFolder/$namePrefix.%05d.$ext" $frame`
if ! ((frame % $feedbackFreq)); then
echo "moved and renamed $frame files to $outFolder"
fi
let "frame++"
done
Pretty sure I need to edit the line for f in *${srcPattern}/* but not sure of the correct syntax

Answer 1

If files in the ND850 folders are sequential when listed (i.e. padded frame numbers), and the folders themselves are in order, then the following code should work.
#!/bin/bash
# Maintain a counter, and the output frame number
let "frame=1"
let "outframe=1"
outFolder="collected"
# frequency
gap=5
namePrefix="ben_timelapse"
#new extension (uppercase is so ugly)
ext="jpg"
srcPattern="ND850"
echo "Copying and renaming 1 in every $gap files"
mkdir -p "$outFolder"
for f in *${srcPattern}/*
do
if ! ((frame % $gap)); then
outfile=`printf "$outFolder/$namePrefix.%05d.$ext" $outframe`
cp $f "$outfile"
echo "copied $f to $outfile"
let "outframe++"
fi
let "frame++"
done

Answer 2

Try this instead of your mv command after do:
if ! ((frame % 5)); then
a=$((frame / 5));
mv $f `printf "$outFolder/$namePrefix.%05d.$ext" $a`
fi
It will move frame=5,10, and so on, to $outFolder/$namePrefix.00001.$ext,$outFolder/$namePrefix.00002.$ext, and so on