Actually i have the same question. Let’s say I have a slider on home page and my pictures on slider are wide pictures (800x300 width>weight). It works well on desktop view, but it will then go messy when I switch it to mobile view. Since mobile view is different (width < height), the pictures are not really scaled to a smaller size, but instead showing only a small portion of the pictures…
I am not sure what to do for this kind of situation, maybe for mobile view we just have to sacrifice certain content of the image. If you make it scale with view port, the picture will become too small to see?