Notes about the LFG file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The LFG file type is primarily associated with 'LensForge' by Ripplon Software Inc.. [Macintosh Program] LensForge is a tool for anyone who designs lens systems, from professional and amateur lens designers, to experimental physicists, to telescope makers. On the Macintosh system this file type is called: ZEMAX lens file