Nokishita – the typically accurate rumors site – received these four images of the two upcoming Canon “big whites,” the 600mm f/4 and the 400mm f/2.8 for the RF mount system.
[Edit: the lenses have been announced officially. Coverage here.]
The pictures show an odd, silver appendage on the camera end of the lens, which looks identical in profile to the cheapest of Canon’s EF-RF adapters. Below is an image of the top half of one lens roughly superimposed on the bottom have of the other to show the gist of the changes:
If this is merely the version III of the EF mount lenses, coupled with an adapter, people will surely be disappointed. That said, even if this is the case, it would presumably use the extra contacts in the RF mount to allow for better image stabilization, exploiting the accelerometers in the lens for IBIS functions in addition to lens image stabilization.
The choice of a silver accent will be annoying to wildlife photographers – as has been commented upon with the other EF lenses used by that group. However, because the silver band now is about an inch along the barrel – rather than a few millimeters – it would be more easily covered by grip tape.
Nokishita, unlike most rumor sites, typically sees a great majority of its leaks prove to be valid product releases. Canon image leaks like this typically precede product launches by a few weeks.
While rumors of an anticipated flagship R1 camera have been downplayed recently, with rumor sites indicating a launch quarters from now, Canon has rarely launched 600mm and 400mm big white lenses in the absence of a new flagship model launching in the same rough timeframe.