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Old Jan 15, 2007, 2:00 PM   #1
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Panasonic, and other manufacturers, in Operating Instructions, confuse Zoom Ratio with Image Magnification. Is the confusion a deliberate sales ploy?

Zoom Ratio is the ratio between the longest and the shortest zoom focal length of the particular camera model. That X ratio can be the same for Zoom cameras that may have very different zoom focal lengths.

In Telescope and Binocular terminology, a "magnification" of 10X does appropriately indicate that on object viewed via that binocular from a particular position appears approximately the same as if viewed from 1/10th the distance, unaided (i.e., from ten times as close.)

In the now commonplace reference (35mm-format photography) the "normal" lens focal length is approximately 50 mm because that focal length produces 35 mm format images of perspective and field of view approximately like that viewed unaided (i.e., 1X magnification.) Therefore, photo magnification is properly the ratio of the lens focal length to the "normal" focal length. At a 12X ZOOM Ratio setting (e.g., 420mm 35mm equivalent) the "magnification" is properly 420/50 = 8.4X (Magnification X) -- thirty percent less than the 12X ZOOM RATIO designation.

However, conversion lens X ratings (e.g., 1.7X) -- unlike zoom ratios -- do properly reflect an additional magnification multiplier. The above 12X ZOOM with 1.7X Teleconverter should have an overall magnification of about 1.7x8.4 = 14.28X.

Many customers are being mislead by the manufacturers literature that carelessly misrepresents Zoom Ratio as Magnification.

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Old Jan 15, 2007, 5:11 PM   #2
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I have no doubt that it confuses some people.......but what would you call a 35mm to 105 mm lens? 3 X... right.
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Old Jan 16, 2007, 1:18 AM   #3
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Daedalus, I don't believe manufacturers are leading customers to confusion.It is a sales pitch, but one that not many newcomers understand fully. Some new buyers stay away from zoom cameras thinking that they don't need all that "magnification", not understanding how versatile a 12X zoom lens can be.
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Old Jan 16, 2007, 3:55 PM   #4
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Perhaps 3Z, or 3ZX, or 3 Zoom, or better, 105/35, (if such designation were really necessary) but definitely not confusing the quite different "zoom factor" with "magnification". Of course, some also do not recognize (nor care) that the the 105/35 designation is actually an arbitrary conventional 35mm-format equivalent, not the actual optical focal lengths.

"X " (i.e., times, multiplier) has long stood for magnification in optical instruments such as microscopes, telescopes, magnifying glasses, etc. Zoom ratio is surely not magnification but it is explicitly misrepresented as such by manufacturers and misunderstood by many purchasers.

Your 105/35 = 3X designation would be the same for a 75mm/25mm = 3X designation that has the same Zoom Ratio but very different "magnification".

Those who choose to photograph unavoidably distant small objects (e.g., birds or animals) are interested in magnification in cameras as well as in binoculars.

Not every amateur photographer fully appreciates the equally valuable versatility and range of as-shot composition and dramatic perspective difference that is afforded by large zoom cameras. Both composition and magnification are important characteristics but they definitely are not the same -- as the manufacturer's literature does imply. The zoom ratio, as such, usefully expresses neither magnification nor photographically significant wide/tele range.
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