IImageMetadata metadata = Sanselan.getMetadata(file);
outputSet = new TiffOutputSet();
TiffOutputDirectory exifDirectory = outputSet.getOrCreateExifDirectory();
{
exifDirectory.removeField(ExifTagConstants.EXIF_TAG_APERTURE_VALUE);
exifDirectory.add(TiffOutputField.create(TIFF_TAG_IMAGE_DESCRIPTION, 0, "abc,pqr,xyz"));