Telescoping Zoom Lens Problems
Telescopic zoom lenses allow a photographer to carry a single lens with a variable magnification range, designed to save time by cutting down on lens changes and provide the user with a way to capture different focal lengths in less time. Due to the way telescopic zooms are constructed, there can be a number of drawbacks to their use.
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Construction
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A telephoto lens with multiple glass elements. Telescopic zoom lenses use multiple other lenses in their construction, and a good zoom lens will have at least three other lens elements. Multiple lenses are designed to bend light and maintain focus over the full focal range of the lens, but imperfections are prone when the lens bends light incorrectly. Any fringes of blue or red light on an exposure--that were not visible to the naked eye--are known as chromatic aberrations and they indicate that the lens has improperly bent light. Fixed-length lenses are less prone to this problem as they contain less elements and surfaces for light to reflect from.
Lens Flare
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Lens flare caused by the sun in the top left of this photograph. Zoom lenses are more prone to the effects of lens flare than others of a fixed focal length. A lens constructed with multiple glass elements will contain more reflective surfaces which, when exposed to bright light, will cause a lens flare effect greater than that seen in prime lenses. This can prove problematic in landscape photography where it's more common to use wide and ultra-wide angle telescopic zoom lenses. You can use a lens hood to help block out unwanted glare, which can reduce the chances of lens flare occurring.
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Speed
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A 50mm fixed length prime lens with a large aperture. A fast lens is considered one that has a large aperture, metered in f-stops, and can allow a lot of light into the camera whilst maintaining a fast enough shutter speed. Fixed-length lenses offer faster performance than zoom lenses, which often offer maximum apertures of f/4 and smaller. Larger apertures--for example f/2.8--provide the photographer with a shallow depth of field and more light, ideal for portraiture or photography where the subject is moving.
Storage
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A camera bag designed to store a digital SLR and one zoom lens. Multiple glass elements add to the weight and size of telescopic zooms, and some larger focal lengths (200 to 400mm) can weight more than 6 lbs. and cover 12 inches or greater in length. Housing multiple zoom lenses requires a large camera bag, which can soon become heavy. Individual fixed-length lenses are often smaller and lighter, though this is not always the case with more expensive, faster telephoto lenses with full metal construction.
Price
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A digital SLR with attached telephoto zoom lens. Due to the complex nature of their construction, telescopic zoom lenses can be expensive. Less expensive lenses are more prone to chromatic aberrations due to lower quality, whereas quality lenses with larger apertures, vibration reduction features and better clarity cost considerably more. For beginners and amateurs, this will not be a problem, but for those looking to upgrade existing equipment it can be an important consideration when deciding on a zoom or fixed-length lens.
Considerations
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A small fixed length lens (left) and a larger zoom (right). Zoom lenses offer clear benefits and disadvantages to their use. Decide whether a carefully thought-out set of fixed-length lenses is the better purchase, providing higher quality images and portability than telescopic zoom solutions. If a zoom is suitable, then buy a lens hood to minimize lens flare and ensure storage equipment is up to the task of transporting and protecting a large addition.
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References
Resources
- Photo Credit inside the lens image by Digimist523 from Fotolia.com micro lens image by jimcox40 from Fotolia.com White Lilacs in the sun image by chuck melino from Fotolia.com camera lens image by dinostock from Fotolia.com camera image by Mikhail Olykainen from Fotolia.com DIGITAL CAMERA image by Gary from Fotolia.com lenses and photo filters image by FrankU from Fotolia.com
