Ever wanted to know how those pentax lenses compare? The lenses are sorted in the legend by max MTF50. The best lens in this respect is at the top etc.
I've spent the last two days testing all of my lenses, now you can compare them for yourself! The nyquist cutoff is theoretically 0.5 for the lens, but the camera has a cutoff around more like 0.34 so that little diffractive line will intercept the origin somewhere around there for an ideal lens (as if you could get a lens faster than 1.4!!)
Anyway, those old pentax lenses are better than you'd think!