I previously owned the Samyang 135/2. I would agree that yes it may be the sharpest of the "inexpensive economy lenses" that you can buy. But it is certainly not sharper than some of the super premium lenses (e.g. Zeiss Otus). Also, as others have said, there are 3 Pentax macro lenses that I believe are just as sharp as this Samyang lens.
There are many characteristics of a lens. I just purchased a $2000 USD lens that I knew was not extremely sharp - but I bought it because it's overall rendering is what I would describe as "creamy/artistic" and I just love the look.
For most of my needs, I'm thinking that most lenses these days are plenty "sharp enough".
If I need sharpness, I just shoot my K1 in the pixel shift mode. I did some PS shooting last night in my studio. The images were totally unuseable because they were far too sharp showing every single spec of dust and smudged finger-print on the shinny metal/glass surface I photographed.
I believe that sharpness is over-rated by many of the Internet lens reviewers, probably because it's one of the lens characteristics that's the easiest to measure.
Last edited by Fenwoodian; 01-21-2017 at 09:36 AM.