I guess many of us were waiting for this: the possibility to use Sigma's excellent…
[Video] The Making of Canon’s EF 500mm F4L IS USM (from the scratch)
Ever wondered how a Canon L lens is made? Well, there is a three part video series (by RazorFantasy) that covers each and any aspect of the manufacturing of the EF 500mm F4L IS USM lens. Above is part 1, below part 2 and 3. Enjoy!