Collection - Add a hover effect to product images on your collection pages

[Pun]

Hello gurus,

may i know why my hover image is not centralised?

.reveal {
  position: absolute;
  top: 0;
  margin-left:auto;
  margin-right:auto;
  width: 100%;
  height: 100%;
}

.reveal .hidden {
  position: absolute;
  z-index: -1;
  top: 0;
  margin-left: auto;
  margin-right: auto;
  width: 100%;
  max-height: 345px;
  opacity: 0;
  -webkit-transition: opacity 0.15s ease-in-out;
  -moz-transition: opacity 0.15s ease-in-out;
  -o-transition: opacity 0.15s ease-in-out;
  transition: opacity 0.15s ease-in-out;
}