The data is captured in the MTF (Central and offset) as well as Field curvature as well as the polychroma c Strehl. Fewer elements combined with high end multicoating increases contrast.
So do you agree with Wes's statement that
"Leica lenses... they have some rendering that is hard to explain in objective* terms. It is often called
Leicaness. The Panasonic-Leica lenses ofr m43 bodies seem to have it too. "?
Because I have no idea what this "Leicaness" is, unless it's one of those terms which be freely redefined as needed. Feel free to quantify this effect for me so that I may better understand.
Quality control is generally superb for Leica
IME, not on the same level as Canon, Sony or Olympus:
Leica M6 factory refurbished: Slight vertical misalignment of rangefinder. (minor)
Leica Trinovid 8x32BA binoculars factory refurbished: Decorative cap fell off.(minor)
Leica M8 brand new: Dust on sensor, infrared contamination, iffy white balance, lines on sensor, poor finder framing accuracy (was annoyed about framing accuracy, eventually addressed in M8.2 and available as non-free "upgrade")
Leica 50/1 Noctilux, brand new: Significant backfocus (major, repaired under warranty)
Leica M9 factory refurbished: Soft/quiet release feature never really did work without firing off multiple shots even in single-shot mode. (minor, factory did not / could not fix)
Oh and speaking of optical performance, when actually used on digital M body, I found that:
50/1 Noctilux had heavy chromatic aberration manifesting itself as blue halos around bright objects. Nothing to be done about it as it was an old design and there was a reason it was discontinued soon thereafter.
28/2.8 Elmarit-M Asph, 35/2 Summicron: exhibited considerable color shift light falloff and softness in corners. Not a defect so much as a tradeoff for optics not optimized for Bayer-type sensor.
I'm not bitter about this because I never expected perfection, particularly not from a small company milling components from blocks of metal and hand-assembling, but at least up until 2012, my experience was that odds of a new Leica product needing at least minor service are much greater than their bigger competitors and that digital M cameras were somewhat beta-quality. Leica USA service was sometimes prompt, sometimes not so much. Love the small size of many lenses but it comes at the expense of so-so corner performance when used with Bayer-type sensor.