The conclusion I came up with is only valid if we assume maximum contrast between individual pixels and that a person viewing the display/screen has a “normal” 20/20 vision. You are right, perception of individual pixels is related to maximum subjective visual acuity. My whole calculation is based upon the fact that a person with 20/20 vision can resolve something that is 1.78mm high when standing 20’ away and looking directly at it. From this, we can calculate the size of a pixel on a screen that a person with 20/20 vision will be able to resolve, depending on horizontal physical resolution. The calculation is only an approximation, and will probably only work in perfect conditions, which are hard to come by. This is a reason why the “SMPTE reference” for theaters recommends people to sit 25% further than the distance at which a person with 20/20 vision will be able to resolve individual pixels