Contrast, sharpness and acuity do not seem to be entirely synonymous.
Actually in my reply I rather thought oft micro-contrast (which effects acuteness)

-) lens aberrations effect microcontrast

-) flare (lack of coating, bad barrel design, lack of lensshade) effects both overall contrast and microcontrast)

Acuteness is the empiric description of what we by vision call sharpness.