In picasaweb (in my web browser), I loaded up the page showing all the photos my friend was in. At the bottom, there was a little "RSS" link. That link looked like this:
I loaded that link in my browser, and it gave me the option to keep it as a live bookmark.
Instead, I trimmed the URL down and plunked it in this little python gdata script:
gd_client = gdata.photos.service.PhotosService()
gd_client.email = 'MY_EMAIL_ADDRESS'
gd_client.password = 'MY_PASSWORD'
gd_client.source = 'exampleCo-exampleApp-1'
print "logged in"
photos = gd_client.GetFeed('/data/feed/base/user/credentiality?kind=photo&subjectids=THE_SAME_BIG_LONG_STRING')
for photo in photos.entry:
That printed out a list of URLs to the images I wanted.