John explains how to use depth of field to your advantage.
Controlling depth of field is a vital technique for any videographer. Defined as the distance both in front of and behind the subject that’s in acceptable focus, by controlling the depth of field you can add an entirely new emotional dimension to your video.
Depth of field is a technique that’s used more often in film that video. Due to physics, the large image plane of a 35-millimeter film makes it a lot easier to control depth of field as opposed to the very small CCD sizes of your camcorder. However, there are certain techniques that you can use even with a small format camcorder that’ll allow you to manipulate depth of field in a pleasing way.
There are two types of depth of field, shallow focus and deep focus, and deep focus is when everything in the picture, from the foreground to the background, is nice and sharp. Videographers often use this style to show great distance and to add dimension and complexity to the frame. For example, if we had a character lost in the woods we could use deep focus to accentuate the vastness of the forest.
Shallow focus is when your subject is in focus but you allow the foreground or the background to get blurry. Now generally this is a technique that’s used to draw attention to a certain character or a specific part of the frame. For example, if our character who’s still lost in the woods is suffering from dehydration, you can use a shallow depth of field to emphasize the importance of that first drink of water.
Here’s what to do if you want shallow focus. Distance yourself far enough from your subject where you have to zoom in all the way for your desired composition. Try to open up your iris as wide as possible by adjusting the shutter speed and using the neutral density filter. The smaller the F number, the shallower the focus. Doing this isolates your subject as being the only plane in focus. A telephoto lens is the easiest way to achieve a shallow depth of focus. Another piece of equipment you can use to get shallow focus is a 35-millimeter film adapter, and essentially this allows you to use a 35-millimeter lens with its very shallow depth of field on your camcorder.
To get a deep focus, use the widest angle possible by zooming out all the way. If you have a wide angle lens adapter this further exaggerates the effect. You want to use the physical placement of the camera to compose your shots and not the zoom lens. If you want a close-up, bring the camera close to your subject while staying zoomed out all the way wide.
If depth of field is a way to show emphasis, rack focus is a way to change that emphasis, and essentially what it is is shifting the field of focus from one subject to another in the same frame. For more information, be sure to check our recent article, Depth of Field Demystified, at VideoMaker.com.
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