I don’t remember thinking about the concept of fast verses slow when I shot this image but once I realized it when I was going through my daily shots, I found the best image out the multiply images I shot at the train station that morning. Because the light was quite dim near the bottom of the frame, I had to keep the shutter speed slow. This allowed for the blurred movement in the person running up the stairs but it was still fast enough to capture a sharp image of the man on the escalator. This may have been a happy accident but I really think I perceived the image correctly in the field only to discover it later when I had some time to evaluate my images.
SONY, SLT-A77V, 50mm F1.4 ZA SSM
1/15, f/5.6, ISO 100