EFL camera refers to a camera system where the key characteristic is its Effective Focal Length (EFL). The Effective Focal Length is a critical parameter defining the camera's field of view and magnification.
Here's a breakdown:
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Effective Focal Length (EFL): This is the distance between the lens's rear principal plane and the image sensor (or film plane) when the lens is focused at infinity. It determines how much the lens magnifies the scene and how wide the field of view is. A shorter EFL results in a wider field of view (more of the scene captured), while a longer EFL results in a narrower field of view (more magnification).
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EFL and Field of View: The EFL directly influences the field of view. A small EFL (e.g., 16mm) provides a wide-angle view, capturing a large portion of the scene. A large EFL (e.g., 200mm) provides a telephoto view, magnifying distant objects and capturing a smaller portion of the scene.
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EFL vs. Back Focal Length (BFL): It's important not to confuse EFL with Back Focal Length (BFL). BFL is the distance between the rear surface of the lens and the image sensor when the lens is focused at infinity. BFL is crucial for ensuring a lens can physically focus on a particular camera body and that there is enough space for any internal components like mirrors in DSLR cameras. The EFL determines the image's size and the field of view.
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EFL in Practical Terms: When choosing a lens, the EFL is a primary consideration based on the desired composition and subject. For example:
- Landscape photography: Often utilizes lenses with shorter EFLs (wide-angle lenses) to capture expansive vistas.
- Wildlife photography: Often utilizes lenses with longer EFLs (telephoto lenses) to magnify distant animals.
- Portrait photography: Lenses with a moderate EFL (around 50mm to 85mm) are often preferred for their natural perspective and flattering rendering of faces.
In summary, understanding the Effective Focal Length is crucial for selecting the right lens for a given photographic purpose, as it directly dictates the field of view and magnification of the resulting image.
