i want to measure something in a picture on a plane. To adjust the picture after shooting it e.g. to do lens correction and de-skewing I want to use a calibration ruler as attached.

What is the professional name for such targets and similar ones as below? What is a common source for material like this?

enter image description here


  • \$\begingroup\$ Photo ruler. One supplier is Lynn Peavey. Look at forensic/crime analysis supply houses. \$\endgroup\$
    – mkennedy
    Apr 24, 2014 at 20:10
  • \$\begingroup\$ commons.wikimedia.org/wiki/File:50_mm_L_ruler_ty.svg \$\endgroup\$
    – db9dreamer
    Apr 24, 2014 at 23:27
  • \$\begingroup\$ Are you sure it isn't called a Bunanupher Scale? \$\endgroup\$ Sep 29, 2018 at 19:27
  • \$\begingroup\$ That... doesn't come up in any google search at all. Are you sure? Can you elaborate? Might there be a different spelling? \$\endgroup\$
    – mattdm
    Sep 29, 2018 at 21:07

1 Answer 1


It is called an "ABFO#2" ruler. Check out the page here. You can also find similar ones following that link.

  • \$\begingroup\$ it is called a forensic corner square according to the link you supplied - the part number is ABFO#2 at that specific manufacturer. \$\endgroup\$ Apr 26, 2014 at 7:13
  • \$\begingroup\$ Actually, you got it wrong, sorry. The "forensic corner square" is the general category or type. See: "The ABFO#2 is the first forensic corner square"... The part number is: "4CSM-WH5x5PL/ORIG". But ... whatever. :-) \$\endgroup\$
    – TFuto
    Apr 27, 2014 at 11:02
  • 2
    \$\begingroup\$ "AFBO" is apparently "American Board of Forensic Odontology" — specifically for bite-mark forensics. Crucially, this isn't at all designed for use in "lens calibration and deskewing" as the question requests. \$\endgroup\$
    – mattdm
    Sep 29, 2018 at 21:09

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