What lens would you consider the sharpest wide open?

[lbenac]

Any slower lens will be sharper wide open. For example, a Protar V. For non-wide angle lenses, a Tessar IIB at F6.3 is sharper than a Tessar IC at F4.5. A Dagor at F6.8 is sharper than most faster lenses, etc.

An easier question to answer (although still largely in the realm of anecdotal evidence) would be which lens is sharpest at f/2.8, or f4.5, or f/5.6...
I can tell you that at f5.6 my 150mm Sironar-S is sharper than my 150mm Xenotar at f2.8 (which is true), but is that a reasonable comparison? Or perhaps it would be better to say that f5.6 my 150mm Sironar-S is sharper than my 150mm Xenotar at f5.6, (also true). Which do you mean? Or better yet, what f/stop do you want to work at?
If you want shallow depth of field you might be better off looking for a long lens, say a 450mm f/9 than a fast and short lens.

Which complicate matters further for un coated lenses, as to me a lens stopped down to 6.3 or 7.7 is not the same than a lens wide-open at the same apertures.
I often like the look of un coated lenses shot with specular highlights on close-up or short distance scenes (ok I might be the only one to like this...).
If the lens is wide-open or in a barrel with 18 aperture blades than the highlights are nice and roundish and blend nicely in the background.
On a "modern" five or even seven blades shutter they are harsh and pentagonal.
Lately I am shooting dialytes (Kodak Anastigmat 203/7.7 and 152/7.7) and tessar (CZJ 135/4.5) wide open and provided the subject can leave with a reduced DOF I am very happy with the sharpness and more importantly how it blends smoothly with the out of focus areas.
So I have contradictory evidence as I would favor slower lens wide open (dialyte 7.7 and tessar 6.3) but the exception is the 135/4.5 which is great even wide open for close-up - key word be for that specific purpose.

Cheers,

Luc