On Thu, Aug 13, 2009 at 3:03 PM, leiz<zhan...@gmail.com
> I think tags/comments and red-eye (for whatever reason) are the only
> operations that change your photos directly. I don't think it can be
> turned off. Keep in mind this only changes the JPEG metadata, and
> doesn't modify the image portion of the JPEG file.
Right, not the 'image portion' of the file, but the file is being changed,
the date changes, the checksum changes, the size changes.
There are benefits of writing metadata to the image file, however
I prefer original images to be immutable.
> The IPTC fields are standard fields that many photo apps understand.
> Would you rather have Picasa store tags in some format that's less
> exchangeable with other apps?
If Picasa is going to write to my files, IPTC is probably fine,
though XMP seems to be the preferred currently.