brightness()

filter: brightness(1);

filter: brightness(1.75);

filter: brightness(50%);

filter: brightness(0);

<section id="default-example">
  <img
    class="transition-all"
    id="example-element"
    src="/shared-assets/images/examples/firefox-logo.svg"
    width="200" />
</section>

brightness(0%)   /* 全黑 */
brightness(0.4)  /* 40% 亮度 */
brightness(1)    /* 无效果 */
brightness(200%) /* 两倍亮度 */