section, footer {
    padding: 20px 0;
}
.parallax-container {
    height: 20%;
}
.parallax img {
    filter: grayscale(1);
    opacity: 0.5;
}

.clients img {
    max-width: 150px;
    filter: drop-shadow(1px 1px 1px rgba(0,0,0,0));
}