Does pin sharp mean in focus or out of focus?
Pin sharp means nothing and everything at the same time.
If people prefer "pin sharp" renderings, then they will pursue them. Other may have a different priorities and they will pursue them. I don't think either choice is inherently superior.
Besides, human perception of sharpness is depressingly complicated.
The International Stands Organization published ISO 20462 to establish a psychophysical image quality measurement standard. This is a three-part standard that attempts to minimize the role of human subjectiveness in evaluating Part 3 of ISO 20462 deals with sharpness.
This
paper discusses the standard's utility.
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Part 3 describes how rulers varying in sharpness may be generated. Sharpness is a good reference attribute because it: (1) is readily varied by image processing; (2) is correlated with MTF, which can be quantified by measurements from standard targets; (3) exhibits relatively low variability between different observers and scenes; and (4) has a strong affect on image quality in many practical imaging systems."
While perceived image sharpness can be quantified using a tedious and complicated process, it is irrelevant to the role of sharpness in creative exoression.
I disagree sharpness is essential to photography. A minimum degree of perceived sharpness is important for documentary work. But are Robert Capa Omaha Beach photos lacking because they are not "pin sharp"? Then there's Henri Cartier-Bresson's work. I was fortunate enough to view some of his original prints. Those prints are not "pin sharp". My subjective perceived sharpness for those prints was more than adequate to enjoy his work.
Also, I don't believe unsharp images are required or inherently more effective for artistic expression.
Visual artists will use different techniques to express their creativity. It is much more difficult for a painter to portray realism than a photographer. But it has been done. Likewise, I think it would be difficult for a photographer to create my subjective experience and responses while viewing Andrew Wyeth's works in person. While legions of people could attempt to reproduce Wyeth's aesthetic using digital image processing, only a small percentage would produce images that come close to succeeding. Another example is tone-mapped rendering (HDR). In my experience a very small percentage of HDR renderings are aesthetically effective. It's easy to render using tone mapping but it's not easy to do it well.