If AF point expansion is selected with an f/8 maximum aperture lens/extender combination, the four AF points surrounding the center point will act as AF Assist points. This option effectively expands the size of the AF detection area to enhance autofocus performance with subjects that are small in the frame and difficult to track, such as small animals and birds in flight. AF points above and below the center will be sensitive to vertical contrast, while points to the left and right will be sensitive to horizontal contrast.Please visit the following website for complete information on the firmware update: www.usa.canon.com/eos1dxfirmwareupdate About Canon U.S.A., Inc. Canon U.S.A., Inc., is a leading provider of consumer, business-to-business, and industrial digital imaging solutions. With approximately $45.6 billion in global revenue, its parent company, Canon Inc. (NYSE:CAJ), ranks third overall in U.S. patents registered in 2011† and is one of Fortune Magazine's World’s Most Admired Companies in 2012. In 2012, for the ninth consecutive year, Canon U.S.A. has received the PCMag.com Readers Choice Award for Service and Reliability. Committed to the highest level of customer satisfaction and loyalty, Canon U.S.A. provides 100 percent U.S.-based consumer service and support for all of the products it distributes. Canon U.S.A. is dedicated to its Kyosei philosophy of social and environmental responsibility. To keep apprised of the latest news from Canon U.S.A., sign up for the Company's RSS news feed by visiting www.usa.canon.com/rss. †Based on weekly patent counts issued by United States Patent and Trademark Office. All referenced product names, and other marks, are trademarks of their respective owners.