Link shows artist drawing at a speeded up pace. Assuming he did this without stopping and no other editing, is there a way to tell how long this actually took him to draw this?
No way to tell. You might count the number of strokes in the picture, but you then have to make assumptions about how long it takes to do each, and how long he spends stepping back (for whatever reason… having a look from a distance, having a drink, resting, etc)
I was going to suggest looking at the forces on his sleeve, to see if you judge the speed of the arm movement… But its rather thick clothing which keeps its place and shape…