Canon's new mirrorless macro lens, the RF 100mm f/2.8 L Macro IS USM, is likely on its way soon, and the first images of it show a bizarre control we haven't seen on a lens before.
On the surface, the RF 100mm f/2.8 L Macro IS USM looks pretty similar to the EF version, but upon a closer examination, you will see it has a second ring with a strange scale next to it with a label that says "SA CONTROL." It is not clear what this is. If I had to guess, this might be a "Stacking Adjustment Control" that could obviate the need for macro rails and instead allow you to focus stack using just a tripod. It is hard to see given the low resolution of the images, but it looks like the left end of the scale (bottom in the picture above) is a minus sign and the right side is a plus sign. Of course, I'm squinting at a low-resolution image and could be totally wrong, but it certainly would a very useful innovation for macro shooters. Another possibility is some sort of control over spherical aberration rendering — the technique used in "soft focus" lenses in the past. Either way, we will likely see the lens and have our questions answered soon!