Thank you for the confirmation Phil and thanks to Bogdan for the idea/thread pointer. I got this working last night and overrode the 0x0016 LensType value as a user defined tag. Although I must admit my PERL is a bit rusty and could not figure out how to reference the existing canonLensType hash for PrintConv in my user defined tag, so I just set PrintConv equal to an inline hash ie. PrintConv =&rt; { num, lens string, .....}