 Sivakumar Paramjothi |
Macro Lens/Telephoto Lens Hi, I am planning to buy a telephoto and a macro lens. When I searched different sites, I came across few lens which are listed as telephoto macro, wide angle macro. I was of the impression that macro lens can only be used for close up shots and got confused when term 'macro' its used with telephoto & wide angle. Can any one please clarify? Also please suggest any good canon telephoto, macro lens of nominal cost. Thanks in advance!
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Bob Cammarata |
True macro lenses are generally fixed focal length and range between 55 and 200 mm. This Link will describe these versitile tools in detail. The Canon EF 100mm f2.8 Macro USM has gotten great reviews. Bob
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Alan N. Marcus |
HiSivakumar, A Macro Lens is a general term for a design that favors close-up photography. All lenses suffer from imaging errors known as aberrations. There are many types of lens errors so the modern lens is designed with multiple elements (individual lens) and groups of elements (elements cemented together). The idea of such a design is to reduce aberrations to a tolerable level. The typical camera lens is designed for best performance when focused on infinity (as far as the eye can see). When so focused, the lens to chip/film distance is about equal to the focal length. When the camera is caused to focus on objects closer than infinity, the lens must move forward away from the film/chip. At Unity (life-size) the lens to chip distance is twice the focal length. At this extended distance a standard lens performs slightly sub-standard. Additionally at this extended distance the image at the film/chip is larger (more magnification), this results in a reduction of light energy reaching the film/chip. The decrease in light Unity is four time (4x). This translates to a 2 f/stop error. Under-exposure often results plus the marks for the f/numbers engraved on the lens barrel are wrong. Compensation for this error is known as “Bellow Factor”. Note that modern cameras compensate automatically for BF as they measure using a meter that reads through-the-lens. Macro lens to the rescue: This design features best performance at Unity (life-size). When focused on infinity this lens is slightly sub-standard. Additionally as the micro is caused to move forward to close focus, a mechanical linkage causes the iris to widen compensating for light loss due to BF. Thanks for reading, Alan Marcus
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Sivakumar Paramjothi |
Thanks Alan, Bob!
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