.mediagrid-item img {
    background: black;
    opacity: 0;
    /*transition: 0.3s ease opacity;*/
    -webkit-transition: opacity 1s ease-in-out;
    -moz-transition: opacity 1s ease-in-out;
    -o-transition: opacity 1s ease-in-out;
    transition: opacity 1s ease-in-out;
}