Each directory can contain a .caption file with information about the various files in said directory.

Features and limitations:
 -The .caption file supports leading and trailing whitespace along with vertical whitespace.
 -Whitespace around the = is optional.
 -Values can be enclosed in " ' or nothing.
 -There are no artificial limitations on date format.  It is treated as a string of text.
 -If a field is present multiple times per file entry then the last entry sequentially is what will be used.
 -If a file entry is present multiple times then the last time a particular field shows up for said file is what will be used.
 -The .caption file does not support recursive directories.  There must be a .caption file for each directory containing files you want to delineate information for.
 -Keys not in the definitive list in Gallery::Caption's @keys array will be skipped.
 -In cases like the size parameter in the below example the code is smart enough to not strip the " from the end.

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Sample entry from a .caption file:

file = test.jpg
 comment = "Drew while under the influence of a concussion."
 copyright = 2000 by nekoken
 date = 2000-06-04
 medium = "Ink on Bristol board"
 size = 11" x 14"
 title = "All Things Fire"

 
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The following keywords are considered valid but check Gallery::Caption's @keys for the most current list.

artist
comment
copyright
date
date_captured
file
height
medium
sequence
size
title
width