Epson Perfection V500 - Manual (Page 56)

Specify a file name prefix with an alphanumeric character string. A 3-digit number is
automatically added to the file name, but you can change the Start Number if you like. If
you are scanning multiple images at once, each image will receive a different 3-digit
number.
Note:
With Windows, the following characters cannot be used in the prefix.
\, /, :, ., *, ?, ", <, >,
With Mac OS X, you cannot use a colon (:) in the prefix.
Select a file format as described in the following table. Depending on the format, the
Options button may be available for making detailed settings.