.  eg)
    [qw(JPEG APP13 Photoshop IPTC)]</td></tr>

<tr><td>PDF_CAPTURE</td><td>Used by PDF module to store information when writing</td></tr>

<tr><td>PreferredGroup</td><td>Preferred family 1 group for writing tags to the current file.
    Not defined to use the default group priorities.  Set in call to InitWriteDirs().</td></tr>

<tr><td>PREVIEW_INFO</td><td>Information about preview image used while writing JPEG
    images only.  This is a reference to a hash with the following entries:
    <table cla