Lester Wareham wrote in post #18778078
What would we hope for for an upgraded MP-E, I suspect the magnification range is too much to achieve an internal focus design?
A near-circular iris.
Autofocus - not for focusing with, but to allow a mirrorless camera to run a rapid stack. So maybe a hybrid.
Start at 0.5x.
I could give up the 5x, it's really no better than cropped 4x, especially with small pixels.
If the optics were to be better then yes, keep 5x. But that's a 10:1 range.
Better CA control.
A smaller diameter front end. Something near the diameter of the hole in the lens cap edIt Hood! would be nice!
One degree of freedom they could use, would be to make it APS-only. I wonder how much it could then shrink.