For many photographers, sharpness and clarity are important aspects of an image. This is why the popularity of super-sharp lenses has been increasing. Almost all modern lenses are now extremely capable when it comes to resolution, but sometimes, this level of ridiculous resolution can become a hindrance.
Sometimes, a super-sharp lens can produce a harsh result. I find this to be more apparent in harsh lighting conditions, like around midday. In these circumstances, diffusion filters can help take some of the edge off and produce a more pleasing look. There's also great for reducing some of the harshness in the highlights, especially in hotspots on skin.
In a recent video, Gerald Undone discusses how these diffusion filters work by demonstrating the new PolarPro Mist Edition filters. I find it quite interesting to see the impact these kinds of filters have on the resulting image. They may not be super useful for photographers; however, for videographers, they're probably quite important. Diffusion filters are used regularly by many cinematographers and filmmakers. The softer, slightly diffused results works to produce a more "cinematic" look. I know I've been considering a set of these filters for many of the videos we produce, so it's interesting to see just how they work.
Check out the full video linked above.