Comparing two lists and finding entries unique to each one

#Get basename from photos folder
$photos_basename = Get-ChildItem \\<server>\Cross_Departmental\Photos\*.jpg | Select-Object BaseName
 
#Get content of SQL output
$identities_basename = Get-Content C:\_admin\identities_basename.txt
 
#Compare SQL string to photos folder basenames and export to txt file, differences found
Compare-Object -ReferenceObject $identities_basename -DifferenceObject $photos_basename.basename | Export-Csv C:\_admin\compare.csv -NoTypeInformation
 
#All differences
$photos_archive = Import-csv C:\_admin\compare.csv
$photos_archive | ForEach-Object { 
$FullPath = ("R:\Photos\" + $_.InputObject + ".jpg")
Copy-Item -Path $FullPath -Destination "R:\Photos\Archive\"
}