Neutral density filters are a must, especially when you leave the house on a subdued day. Those days that suddenly change to a very bright sunny day, and the film is too fast and can’t expose properly in strong sunlight. When a neutral density filter is screwed into the front of the lens, it slows down the film. In other words, you have a 400 ISO film in the camera. The neutral density filter effectively slows the ISO 400 rating to a 200 ISO rated film. This depends on the darknesses of neutral density filter you use. The darkest filters can slow a 400 ISO right down to 100 ISO depending on the extent of sunshine during the day. There is also a very light filter, included in the pack. This lighter neutral density filter is good for slowing the film ISO rating down a little. I don’t want to get too technical. Let’s say you are photographing on a windy day, there is long grass that is swaying in the wind. The slightly lighter filter slows the camera controls down. This would create movement in the grass, it is a really nice effect if you take a photo of countryside with a cottage in. The difference between some creative blurring can create mood to a photo.These neutral density filters work equally well with digital, if applied in a similar way to film.