Caldwell Photographic and Metabones have announced the Speed Booster Ultra for Micro Four Thirds: an updated design that uses more sophisticated glass and has been optimized for use with the relatively thick Micro Four Thirds filter stack. The latest Canon version also gains AF-S autofocus when used with Panasonic cameras: an improvement available via firmware update for existing users. Read more
Articles: Digital Photography Review (dpreview.com)