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Old Jan 25, 2007, 9:38 AM   #1
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Join Date: Dec 2006
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I have a KM 5D body, with myMaxxum 50mm 1.7, 35-70, and 70-210 f4 lenses that came with my old 7000. A friend is getting rid of some of his gear and has a teleconverter for his old 7000i he wants to sell me. Does the teleconverter just double your focus range of a lens? (IE: the 70-210 becomes a 140-420)

Also, do you lose any performance usingone, such as the 50mm no longer having f1.7 capability, losing auto focus, etc. Thanks!
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Old Jan 25, 2007, 6:16 PM   #2
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Join Date: May 2005
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Teleconverters increase the magnification of any lens they're mounted to. On SLR's they fit between the body and the lens and many TC's are chipped to allow for correct communication between the body and lens. TC's do lose light, typically between 1 and 2 stops, depending on their magnification. ( a 1.4x would lose 1 stop, a 2x would lose 2 stops) Most bright lenses will autofocus when a TC is mounted, but below about f5.6 don't count on autofocus. It may hunt a lot or just be unable to lock. There is also a sharpness penalty as TC's ad glass between your subject and the sensor, which always degrades quality, some more than others.

I bought a 2x TC, and have only mounted it once. I didn't like the image quality. (but it was a cheapie)
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