According to a moderator’s posting in Canon USA’s official forums, Canon will be releasing a firmware update for the 5D Mark III and 1D X to correct an issue where the camera’s are slow to focus when used with a Speedlite’s AF Assist Beam.
Hi all, we have an important update on this topic. Thanks again for your feedback on our Forum.
Canon has confirmed that, depending upon the shooting conditions, it may take slightly longer for the EOS 5D Mark III and EOS-1D X digital SLR cameras to acquire focus when using the Speedlite’s AF Assist Beam, compared with that of the EOS 5D Mark II and EOS-1D Mark IV digital SLR cameras using the Speedlite’s AF Assist Beam. We are developing a firmware update to enhance the focusing feature for the EOS 5D Mark III and the EOS-1D X. The schedule for release of this firmware update will be announced shortly.
Of course, we’ll have more details and download links once the official firmware ships.
[via Canon USA]