Canon will soon launch the RF 100mm L Macro, the long-awaited replacement to the EF version. It appears to have a magnification of up to 1.4x. This time, though, in addition to the three sets of controls for AF/MF; focus limiters; and image stabilization, it dedicates a third ring to an as-yet unknown adjustment labeled “SA Control,” which has four notches of plus and four notches of minus. The pictures were leaked to Nokishita. [Update: Nokishita indicates – without citing a source – that the SA Control ring manages a spherical aberration feature Canon recently patented, effectively giving some control over sharpness and bokeh in the background.]
It might be a sort of focus rack control, allowing for a tripod-mounted lens to engage in a series of shots for focus stacking. Canon had some patents for this to be done in an automated way some years ago, without a product surfacing using the technology.
Similarly, the new control could be in reference to the patent published recently that provides for an extra control, in addition to focus, that would make aberration correction adjustments optimizable to such factors as distance to the subject and possibly provide a “soft focus” capability for backgrounds.
Otherwise, the lens looks very much like an RF version of the EF lens of yore, but for the addition of the new customizable RF ring at the end of the lens. The size looks to be very similar.