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8.4: Lens Movements

  • Page ID
    124333
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    What is a Lens Movement?

    Lens movements happen when individual pieces of glass within a lens move, making objects in the image appear closer or further away. Most video cameras have zoom lenses, but if you are using a cinema camera, DSLR, or mirrorless camera, you will need to make sure the lens you are using is a zoom lens, which allows for variable focal length. You can learn more about zoom lenses in Chapter 7.10.

    Zoom

    The camera lens moves to make it look like we are getting close to a man's face.
    Figure \(\PageIndex{1}\): Zoom in to person's face. (CC BY-NC 4.0; Shelley Ho via San Francisco State University)

    A Zoom gives the appearance of moving closer or further away from the subject without moving the camera itself (See figure 8.4.1). It differs from a dolly in that instead of moving the camera itself, you are moving the glass in a lens to change the field of view. You can zoom in to get a closer detail of a subject or zoom out to reveal details of a room or a landscape, for example.

    Rack Focus

    The camera changing focus from a man closest to us to a woman behind him.
    Figure \(\PageIndex{2}\): Rack focus from one person to another. (CC BY-NC 4.0; Shelley Ho via San Francisco State University)

    Rack focus is a change in the focus of the camera. This requires the manipulation of the depth of field, which we will discuss later in this chapter. This movement is another glass movement inside of a lens, but a much smaller glass movement than a zoom. If person A is in focus and closer to the camera, person B can be placed further away from the camera and will appear out of focus. When you change the focus from person A to person B, that is a rack focus (See figure 8.4.2). After this movement, person B will be in focus while person A is out of focus. Any time you change which subjects are in focus it is called a rack focus.


    This page titled 8.4: Lens Movements is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Christopher Clemens (ASCCC Open Educational Resources Initiative (OERI)) .

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