標準偏差

html,
body,
svg {
  height: 100%;
}

<svg viewBox="0 0 480 200" xmlns="http://www.w3.org/2000/svg">
  <filter id="gaussianBlur1">
    <feGaussianBlur stdDeviation="1" />
  </filter>
  <filter id="gaussianBlur2">
    <feGaussianBlur stdDeviation="5" />
  </filter>
  <filter id="gaussianBlur3" x="-30%" y="-30%" width="160%" height="160%">
    <feGaussianBlur stdDeviation="10" />
  </filter>

  <circle cx="100" cy="100" r="50" filter="url(#gaussianBlur1)" />
  <circle cx="240" cy="100" r="50" filter="url(#gaussianBlur2)" />
  <circle cx="380" cy="100" r="50" filter="url(#gaussianBlur3)" />
</svg>