Explanation of Optical Zoom
Optical zoom--not to be confused with digital zoom--employs optics allowing a camera to magnify a distant subject without moving closer. Although most often advertised as a selling point with "point and shoot" cameras, the concept of optical zoom also applies to lenses available for use with a single-lens reflex (SLR) cameras.
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Optical vs. digital
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An optical zoom is infinitely more valuable than a digital zoom. Do not confuse optical zoom with digital zoom. While optical zoom brings an object closer, Kodak notes that, "digital zoom crops your image and magnifies the result of the cropping." The action of cropping an image results in a loss of photo resolution and image quality. Optical zoom is infinitely more valuable to a photographer and, consequently, more expensive.
Mechanics
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A zoom lens uses optics to magnify a photographic subject. A zoom lens is composed of numerous glass elements and moving parts. Image magnification is accomplished by changing the distance of the lens center from the camera's sensor.
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Zoom
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An optical zoom has a variable focal length. Camera lenses are either prime or zoom. Whereas a prime lens has a fixed focal length (as in 100mm), an optical zoom lens has a variable focal length (as in 70-200mm). The variable focal length of the optical zoom offers greater flexibility for the photographer.
Optical power
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An optical zoom is measured in a power of X. Optical zoom is often measured in a power of X, as in 10X. What does that actually mean to the layperson? If you are using a 28-280mm lens, that's equivalent to a 10X optical zoom. According to Digital Photography Review, "This means that the size of a subject projected on the film or sensor surface will be 10 times larger at maximum tele (280mm) than at maximum wide angle (28mm)."
Applications
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An optical zoom is perfect for capturing distant wildlife. Applications for using an optical zoom include portrait work, sporting events and wildlife shots. Optical zooms can also be used to capture close objects. When an optical zoom is extended to its maximum telephoto capabilities, the photographer can take advantage of a shallow depth of field. Depth of field defines what is in sharp focus; with a shallow depth of field, only a small portion of the photograph is in sharp focus. The advantage of this is that it's easy to blur out a distracting background or foreground.
Lens quality
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Your budget will dictate the range of your optical zoom. Optical zoom lenses come in a variety of focal lengths, speeds (indicated by the largest aperture or lens opening), and optical quality. Both your planned use for the lens and your budget will dictate your purchase.
Practice
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Extensive use will help you master your optical zoom. An optical zoom will broaden your photographic horizons exponentially. As with any new piece of equipment, practice is essential. Giving yourself photo assignments is a recommended method to familiarize yourself with the lens and perfect your technique.
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References
Resources
- Photo Credit film-camera on camera-bag image by Andrii Oleksiienko from Fotolia.com heron image by karamba from Fotolia.com zoom lens image by leafy from Fotolia.com photographe ancien image by bacalao from Fotolia.com lens image by Vasiliy Koval from Fotolia.com bald eagle image by MAXFX from Fotolia.com winter shoot image by Alexey Klementiev from Fotolia.com the photographer image by Harvey Hudson from Fotolia.com
