Shutter Speed for Motion Calculator (Freeze or Blur)

Because they assume a typical distance and lens: 1/500 freezes a footballer at 30 m through 200mm, but the same player filling the frame at 8 m moves 4× faster across the sensor — needing 1/2000. Conversely a distant subject through a wide lens barely moves in pixels at all (the reason phone videos of far-off action look fine). The invariant is pixel velocity: this tool computes it, and the rules emerge as special cases of one formula.

You're photographing the velocity's projection onto the sensor plane: across-frame motion projects fully; 45° motion at cos 45° ≈ 71%; head-on motion projects only its small apparent-size-change component — roughly 10–20% of across-frame speed at sports distances. Practically: shooting from a corner where the action approaches buys you 2–3 stops of shutter for free, which is why experienced shooters position on the diagonal and why head-on cycling shots stay sharp at speeds that would smear a side-on pan.

Invert the goal: track the subject so IT stays still on the sensor while the background streaks — now shutter sets background blur, and the subject's sharpness depends on your tracking smoothness. Standard ladder: 1/125–1/250 for gentle environmental streak, 1/60 for classic motorsport, 1/30–1/15 for dramatic full-streak panning (with a monopod and practice). Imperfect tracking residual is the limit: most photographers' panning keeper rate collapses below 1/30 — exactly the error this tool's pixel-budget framing makes visible.

Two independent blur sources adding together: the 1/focal-length rule budgets SHAKE (a 200mm needs ~1/200 handheld, before stabilization buys its 3–5 stops back), while this calculator budgets SUBJECT motion — and stabilization helps only with the first. The governing shutter is the faster of the two requirements; for sports through long glass, subject motion nearly always wins, which is why IS-equipped 600mm wildlife shots still demand 1/2000 when the bird flies but allow 1/60 when it perches.