In convert_lens() changed 'try' test to 'hasattr' test (Campbell Barton's suggestion, thank you), added '_' between prefix and ob_name to get more readable layers' names in AE, plus minor spelling corrections.

modified def convert_lens to behave correctly when camera sensor fit is set to vertical.\nPrevious version worked accurately only when 'AUTO' or 'HORIZONTAL' sensor fit was used.\nPreserved compatibility with 2.60a not supporting camera sensor size.