Resolution goes back even farther than that, to the number of line pairs that could be "resolved" (distinguished from one other) in an image. It was a way to co

Resolution goes back even farther than that, to the number of line pairs that could be "resolved" (distinguished from one other) in an image. It was a way to compare the ability of imaging systems to capture and accurately display fine detail. With digital sensors and screens you can pretty much just calculate it directly since you can't resolve detail below the pixel level. But, note that moire can eliminate fine detail well above pixel level if not controlled. Before that, there were standard targets with fine lines in tight tapering patterns. Folks would take a picture of the target with a particular lens and film, and then count the smallest line pairs they could make out before the taper disappeared into an undifferentiated blur. By varying lenses and films, they could compare resolution. Example: https://www.onlandscape.co.uk/2014/12/36-megapixels-vs-6x7-velvia/ https://www.onlandscape.co.uk/2014/12/36-megapixels-vs-6x7-v...