To achieve the best quality from all Super Angulon XL and rodentock apo grandagon/ same apo sironar digital lenses they must be calibrated at Schneider/Rodenstock for the shutter.
The frontelement will be calibrated with very thin rings, so the front element should never be open again to keep the best quality.
The deference between factory calibrated lens and a lens that is just puted in a shutter is at these spcial wide angel lenses really big.
All extrem wide angles: SA XL 38 mm, 47 mm, 58 mm, and A.Grandagon 55 mm should give you best sharpnes in extrem corners untill the end of the image circle.
for the 58 xl you must use aperture 22, for A.G. 55 mm aperture 16 should be enough. Both will cover full 4x5" with a little bit movement, without soft corners.
I prefer rodentock 55 that I use also for digital work at aperture 8,11,16 it is really great lens, but schneider should work at analoge in same way, otherways the lens needs calibration.
sorry for my english.