find_duplicate_files.ps1

# a list of paths to retrieve files from
$paths = @(
	'databak\DCIM'
	'DCIM'
)

# a dictionary to store the hashes
$hashes = new-object 'System.Collections.Generic.Dictionary`2[string, System.Collections.Generic.List`1[System.IO.FileInfo]]'

# compute the hashes of all the files
get-childitem -path $paths -recurse -file | foreach {
	$hash = get-filehash -path $_ -algorithm 'MD5'

	if( -not $hashes.ContainsKey($hash.Hash) ) {
		$hashes.add($hash.Hash, (new-object 'System.Collections.Generic.List`1[System.IO.FileInfo]'))
	}

	$hashes[$hash.Hash].add($_)
}

# $hashes holds a dictionary where keys are hashes and values are lists of
#   files having that hash.

# count duplicate files
$hashes.getenumerator() | where { $_.value.count -gt 1 } | measure-object