Shutter Speed to Freeze Motion Calculator (Motion Blur)
Find the slowest shutter speed that freezes a moving subject from its speed, distance, focal length, sensor size and resolution, or see how many pixels of motion blur a shutter speed gives.
How it works
magnification m = f ÷ (distance − f) · image speed = subject speed × m × direction factor (across 1, diagonal 0.71, toward ≈ 0.25) · pixel pitch = sensor width ÷ image width in pixels · slowest shutter = acceptable blur (px) × pixel pitch ÷ image speed
A moving subject smears across the sensor at its own speed multiplied by the lens magnification. If the smear during the exposure is smaller than a pixel or two it looks frozen. Long lenses and close subjects magnify motion, so they need faster shutter speeds; high-resolution sensors with small pixels show blur sooner. Motion toward the camera barely moves across the frame, so classic exposure tables allow about four times slower speeds. Panning with the subject cancels most of the motion and is how sports photographers freeze fast cars at 1/250 s.
Worked example
A cyclist at 30 km/h (8.33 m/s) crosses the frame 10 m away, shot at 50 mm on a 6000-pixel-wide full-frame camera. Magnification is 0.05 ÷ 9.95 = 0.00503, so the image moves 41.88 mm/s; with 6 µm pixels and 2 px of allowed blur the slowest shutter speed is 0.012 ÷ 41.88 = 1/3490 s — use 1/4000 s.
Sources: Wikipedia — Motion blur · Wikipedia — Magnification (photography)
Frequently asked questions
What shutter speed freezes motion?
It depends on speed, distance and focal length. As a rough guide: people walking 1/250 s, running children or pets 1/500–1/1000 s, cyclists and ball sports 1/1000–1/2000 s, birds in flight and motorsport 1/2000–1/4000 s.
Why do telephoto lenses need faster shutter speeds?
They magnify the subject, and with it the subject's movement across the sensor. Doubling the focal length doubles the image speed and halves the slowest usable shutter time.
How much blur is acceptable?
One or two pixels is invisible even at 100% on screen; around five pixels still looks sharp in web images and small prints. Use a smaller number for large prints or heavy cropping.
Does panning change the answer?
Yes. If you follow the subject smoothly, its image barely moves on the sensor and you can use much slower speeds — the background blurs instead, which is the panning effect.
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This calculator is for educational purposes. Double-check important results before acting on them.