As for Zeiss lenses vs Schneider lenses for the Rolleiflex 6000/Hy6/AFi systems: I believe Brad is using very large aperture lenses from Schneider. By their nature they should not be compared to smaller aperture lenses with the same focal point. Large aperture lenses will in general be softer with three dimensional surfaces, especially at short distances, because of their large front lens diameter. Due to this diameter they will see "around" small details/objects (at short distance), giving strong optical blur just outside the maximum focus area. Focused on a flat surface (like a focus target) they might seem just as sharp as Zeiss lenses though. The more "standard" Schneider lenses for this system are generally sharper than the Zeiss designs. Schneider lenses use more modern lens designs too, which might be one of the reasons for the better performance.
I think EPd may have hit the nail on the head, although very little of my work is at close distances.
In particular the 80/2 is markedly inferior (in terms of resolution) than the 80/2.8, even when stopped down to 2.8, regardless of focusing distance. It's the nature of the beast (I've checked several units). It is not hard for me to imagine the same is true of the 180/2.8.
Checking the MTF's should tell the tale, certainly for resolving capability. And looking at the Schneider Tele-Xenar 180/2.8 vs. the Zeiss Sonnar 180/4 CFE for example, the Zeiss outperforms with significantly higher (+0.2) resolution (40lp/mm) and lower astigmatism.
Two weeks ago, I evaluated the AFD 50/2.8 on a hike and found its corner performance to be disappointing, even on a 48x36mm sensor, focused at infinity and stopped down to f/5.6-f/8. I have not compared it with the Zeiss FE 50/2.8, so I cannot speak to relative performance. But there does seem to be a very real penalty for speed (beyond price and weight).
MTF's show that going to a Distagon 50/4 FLE would show an improvement, at the cost of half the light sensitivity...
I have little doubt that much of the difference I see, as EPd points out, is due to compromises that must be made for such high-speed optics. All of my Rollei lenses are at least 1/2 a stop but usually a full stop faster than my Hasselblad Zeiss counterparts.
So yes, I'd consider doing an apples-to-apples comparison with slower glass to more fairly compare the two lineups.
Very good point, EPd, thank you.
Based on what I've seen above, it does not surprise me that the Mamiya's 80/2.8 outperforms the Contax 80/2.0, even stopped down. Also the Contax Sonnar is, IMHO the weak lens in Contax' lineup, so that makes sense as well. The 45 test is interesting, but I have not tried the 45 in either lineup. I'd like to see MTF charts for the Mamiya wides--do you know where one can find Mamiya MTF charts?