Fineness aside, the main quality you want in your ground coffee is a very even size distribution around your desired size. If a lot of the resulting grinds are smaller or larger, especially very fine dust, the resulting brew will be much less balanced. If you want to, you can buy a sifter set to sort out different particle sizes. If you really want to, there’s software to do optical size distribution analysis.
Fineness aside, the main quality you want in your ground coffee is a very even size distribution around your desired size. If a lot of the resulting grinds are smaller or larger, especially very fine dust, the resulting brew will be much less balanced. If you want to, you can buy a sifter set to sort out different particle sizes. If you really want to, there’s software to do optical size distribution analysis.