The idea of measuring SRA using a digital microscope seems to be about as current as last year‘s high fashion. In recent weeks or months, there have been a few convincing posts by knowledgeable persons in the field suggesting that most of us would not know how to use the microscope to determine the true rake angle of the stylus, because it requires an intimate understanding of the geometry of the stylus tip you are dealing with. And modern styli are very complex in shape.It's not just the stylus shape that makes it difficult. The reality is that it takes a big change at the pivot-end to make an audible difference at the stylus end. I had VTA on-the-fly 30 years ago, I wanted that magic 'snap into focus' moment. But it took very large adjustments to hear any meaningful change. It was a VDH 1 stylus, with a very sharp edge — it should have been dramatic. I was so disappointed.
This puts it in perspective...
https://www.tnt-audio.com/sorgenti/vta_e.html