Click the Canon Digital Learning Center (CDLC) link below to access the in-depth article on the EOS System:
What's New: 320EX, 270EX II Flash Release Function
Note: If the link does not respond, paste this URL into the address bar of your browser:
http://www.learn.usa.canon.com/resources/articles/2011/whats_new_320ex_270exii_article.shtml