To increase icon sizes relative to their container, use the fa-xs, fa-sm, fa-lg (33% increase), fa-2x, fa-3x, fa-4x, fa-5x, fa-6x, fa-7x, fa-8x, fa-9x, fa-10x classes.
<i class="fas fa-camera fa-xs"></i>
<i class="fas fa-camera fa-sm"></i>
<i class="fas fa-camera fa-lg"></i>
<i class="fas fa-camera fa-2x"></i>
<i class="fas fa-camera fa-3x"></i>
<i class="fas fa-camera fa-4x"></i>
<i class="fas fa-camera fa-5x"></i>
<i class="fas fa-camera fa-6x"></i>
<i class="fas fa-camera fa-7x"></i>
<i class="fas fa-camera fa-8x"></i>
<i class="fas fa-camera fa-9x"></i>
<i class="fas fa-camera fa-10x"></i>