The 75mm Heliars are mentioned favorably by several here; I have both and like them too. Here are some comments about the optics...
f/1.8 75mm... Is it a Heliar optically as well as by name? The only Voigtlander Heliars with a true 5/3 Heliar block diagram are the two 50mm Heliars. But this one is close, differing only in having the center negative group made up of a cemented pair instead of a single element. A Heliar in spirit, then, and interestingly almost identical to the old 73mm f/1.9 Hektor, even close to the actual focal length and aperture. Heliar's specs say 33.2° angle of view which calculates to 72.6mm...
f/2.5 75mm... Optical arrangement looks like a regular 6/4 Planar pattern, nothing there to criticize. Sean Reid's review of this lens on the Leica M9 shows some corner illumination fall-off at f/2.8 and wider, essentially gone by f/4, and very slightly cyan in the outer zones. Advises turning off Lens Detection, as otherwise the camera tends to overcorrect both issues. There is no focus shift, and the sharpness center and corners equals the f/2 Summicron at all stops (not tested beyond f/8). Moderate blue/purple fringing in strong backlight wide open, almost gone by f/5.6, lower flare than the 'Cron or Summarit. Just a tiny bit of pincushion distortion. Tends toward doubling in far-bokeh, a bit moreso than the 'Cron. Very impressive, and he calls it a standout performer in the CV line.
