A Focus on Focus (page 2)
Getting Creative
Rack-focus can be quick or slow. An obvious example of a slow shift would have the camera go in and out of focus to show the character getting drunk or driving tired. Another way would be to have the scene slowly go completely out of focus to show the character passing out, perhaps from injuries. This can be done as a point of view shot (POV) or not, but the audience will understand what is going on if it is well done.
The same sort of trick can function as a transition. You can have the scene go totally out of focus and then cut (or even better, use a quick dissolve) to a new scene that starts out of focus and slowly sharpens. For instance, you could do this to show the hero waking up in a strange location.
Using focus thoughtfully to lead your audience's attention can be subtler than a pan or a zoom. Focus can be an almost invisible curtain that strikingly reveals your story. You can control where they look and what they see, but they are rarely aware of how you do it. Suddenly, what was right before our eyes all along becomes obvious and the impact can be magical.
Gene Bjerke is a freelance scriptwriter and author of Writing for Video.
Sidebar: Depth of Field
Most lenses do not render everything in front of them sharply, which is why we need to focus. There is a zone of maximum sharpness and objects in front of or behind this zone are softer. The range of acceptable sharpness is the depth of field.
In general, the area of acceptable sharpness extends twice as far behind the focus point as it does in front. Besides that, there are three factors that determine the total extent of the depth of field.
- Focal length - Longer lenses have less depth of field than shorter lenses. Thus, when you zoom in, your depth of field gets shallower.
- Aperture - Any given lens will have greater depth of field as the aperture gets larger and the f/stops get smaller. Thus if you can adjust your f/stop, you can change your depth of field. Unfortunately, small cameras have inherently small apertures, so there is only so much you can do to get that artistically narrow depth of field, especially in low-light conditions.
- Distance - The closer the camera is to the subject, the shallower the depth of field. Thus to get a shallow depth of field, place your subject close to the camera.
Sidebar: Focus Controls
It is a rare camcorder that allows you to focus by manually turning a lens element directly. In many cases, you might press a button or dial a wheel to focus. Even if you can adjust the focus using a ring on the barrel of the lens, it usually only transmits an electrical impulse that runs the motors that control the focus. A true mechanical focus is best. Usually you can tell what you have by the feel, by the fact that the focus ring has a limited range (i.e. it doesn't go around and around in the same direction) and by the distance markings on the barrel. These markings allow professionals to rack focus almost instantly without even looking in the viewfinder. Using the focus motors on most cameras does not allow such lightning and accurate adjustments. Unfortunately, manual lenses are expensive, and therefore rare, in sub-$5,000 camcorders.
