.jumbotron{
    background: url("image-url") no-repeat center center;
    -webkit-background-size: 100% 100%;
    -moz-background-size: 100% 100%;
    -o-background-size: 100% 100%;
    background-size: 100% 100%;
    background-size: cover;
    height: 78vh;
    filter: brightness(50%);
}