As most of you know, Canon released a firmware update for the Canon EOS-1D X that enabled the highly sensitive auto-focus center-point to be used with apertures down to f/8. That was an important addition to the feature set of the EOS-1D X.
However, it turned out that some EOS-1D X models are not center-point focusing using f/8, despite the firmware. Apparently this happened to EOS-1D Xs that were sent in for service and returned with a firmware update.
It’s easy to find out if your EOS-1D X is affected. Check the serial number, if the sixth digit is a 4 or 5, then open the battery compartment and look out for a white dot in the position shown in the pic below. If the small white dot is there, your camera is not affected.
If your camera is affected, simply download the latest firmware update (1.2.1, click here to download) and install it on your own. Btw, the EOS-1D X is still available at the incredible price of $5,907.82 (click here) on eBay.