Scripting iPhoto, Graphic Converter - copy photo Comment to IPTC caption

Question

I want to select a bunch of photos in iPhoto and have the iPhoto comment for each file copied into its IPTC caption.
The script below works without throwing an error but the IPTC caption contains some trailing garbage in about 1 out of 3 photos. How to eliminate garbage?
tell application "iPhoto"
set selectedPhotos to selection
repeat with thisPhoto in selectedPhotos
set thisPath to image path of thisPhoto
set thisPath to (POSIX file thisPath) as string
set theComment to comment of thisPhoto
copy theComment to theCaption
tell application "GraphicConverter"
activate
try
set iptcinfo to get file iptc of thisPath
on error errMsg number errNbr
set iptcinfo to {"", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "-1", "", "", ""}
-- no IPTC in file so make one
end try
set the first item of iptcinfo to theCaption
set file iptc of thisPath to iptcinfo
end tell
end repeat
--copy the iPhoto comment to the iptcinfo
end tell

Answer 1

I'm not good with scripting however to get the description applied to the IPTC description field, you can use iPhoto. All you have to do is use the Export option, select JPEG and then check the check box about including the title and description data. I've verified it is included with Exifer a freeware program for PC. Although the data is there, it is not read by Picasa on PC despite also reading and writing the caption to the IPTC description file. Do you think the extra garbage might also be being written by iPhoto and hence stopping Picasa from recognising the data? I'm using iPhoto 7.1.1 (354). Any help or suggestions to get descriptions written to IPTC would be great! Cheers.