if (!_directory.containsTag(ExifDirectory.TAG_COMPRESSION)) return null;
if (!_directory.containsTag(ExifDirectory.TAG_FOCAL_PLANE_Y_RES)) return null;
    public String getFocalPlaneYResolutionDescription() throws MetadataException    {        if (!_directory.containsTag(ExifDirectory.TAG_COMPRESSION)) return null;        Rational rational = _directory.getRational(ExifDirectory.TAG_FOCAL_PLANE_Y_RES);        return rational.getReciprocal().toSimpleString(_allowDecimalRepresentationOfRationals) + " " +                getFocalPlaneResolutionUnitDescription().toLowerCase();    }