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11-21-2007, 04:42 PM   #1
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f/2.8 + TC1.4x =

Survey says?

11-21-2007, 05:05 PM   #2
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=f4. .
11-22-2007, 05:54 PM   #3
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from what i HEAR, with a 1.4x factor, f4.
11-23-2007, 12:21 AM   #4
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2.8•1.4=3.92. Pretty close to 4, eh?
The long answer is that you've increased the focal length by 1.4•, but not the entrance pupil, and that translates to a one stop loss of light at the film plane. Teleconvertors are typically either 1.4• or 2• so the result is easily calculated- one stop or two.
I've yet to use a good TC, usually you'd be better off cropping it seems. I've used Pentax branded A-series ones only, but doubt 3rd party ones would be better.

11-23-2007, 12:31 AM   #5
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2.8*1.4=3.92
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