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Old Feb 24, 2009, 2:04 PM   #1
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I own a Casio EX-F1 (12x optical zoom, f=7.3-87.6mm 1:2.7-4.6 diameter: 62mm) that i fit with a Raynox DCR-2025PRO 2.2x teleconverter lens. How big is my final zoom from walkaround human view ? 14.2x or 26.4x?

Same question for a Panasonic DVC cam with 30x optical zoom (f=1.9-57.0 mm) fitted with a 30.5mm teleconversion lens. Does it amount to 31.4x optical zoom or 42x optical zoom?

Thanks for explanations

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Old Feb 24, 2009, 4:16 PM   #2
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The 'X' is the ratio of the smallest focal length to the longest focal length. Your Casio EX-F1 has a lens with a zoom range from 7.3mm to 87.6mm. That gives a zoom ratio of 87.6/7.3, or 12.

When you mount the 2.2X teleconverter, you're lengthening the focal length of the lens by 2.2 times. The result is a lens with a zoom range from 16mm to 192.7mm. That gives a zoom ratio of 192.7/16, or 12. It's still 12 because the teleconverter multiplied both the shortest and the longest focal lengths by the same 2.2, so the ratio of the shortest to the longest is unchanged.

But if what you're looking for is a way to state the potential coverage of your photographic system, with and without the teleconverter, that would be 192.7/7.3, or 26.4.
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