Daytime Exteriors

Lighting for Digital Video and Television has a similar section on outdoor lighting tips...

There are more complex difficulties when lighting outdoors simply because you can't control the sun. Clear days are too contrasty and overcast days don't provide enough contrast. The sun will act as a hard light source on clear days and will be at its worst at midday what with the inherent ugliness of direct overhead lighting. The most forgiving day you can hope for is one where there is just a little cloud to diffuse the light but not too much.

Quite often you will just have too much light in all the wrong places. Use reflectors, beadoard and white card to act as keys, fills or backlights and redirect the light. In areas where the light needs to be softened or taken down a notch, nets and diffusion fabric should be placed accordingly to absorb the rays.

On an overcast day one wants to create contrast as grey light is coming from all angles. You'll either want to add light or take it away. Adding light will of course consist of either adding an actual light such as an HMI or using more reflectors. The second option is to create negative light using a large black flag placed close to the subject off camera. This will block light from one side as well as absorbing any light coming from the other direction.