Controlling Contrast is difficult in bright sunlit exteriors. Exposing for either highlights or shadows will leave the other severely under-or over-exposed.
Tiffen Filters 4"x4" Low Contrast filters work by spreading light from the highlights to the darker areas. Shadows are lighter, enabling you to see more detail. They also create a very slight flare or halation around hot spots which can be a useful effect. Low Contrast is the filter of choice for people who shoot video but want to achieve more of f film look.