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Old Feb 7, 2009, 12:19 PM   #1
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You'd think this lens couldn't do anything this tight in with any kind of sharpness when a 1.4 TC is attached. Not so my friends. Also the Bigma with the APO Teleconverter will go down to 58mm and not just to 100mm as some would think...well here is the photo proof of the above...also the F/stop is as tight as the lens would allow too...so the theory that you can't focus above f/8 or so is not true with this combination. I don't believe any of these are below f/22. Those flower and bug photos are obtainable with out a lot of lens changing when on a walkabout with this combo.

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Old Feb 7, 2009, 12:20 PM   #2
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Old Feb 7, 2009, 12:20 PM   #3
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Old Feb 7, 2009, 12:21 PM   #4
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Old Feb 7, 2009, 12:21 PM   #5
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Old Feb 8, 2009, 6:32 AM   #6
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Good to know, although I'll probably never own a Bigma

Details are there, I'd like to see a ISO200 (or even better, a ISO 100) shot. Also the bokeh isn't to distracting.

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Th.
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Old Feb 8, 2009, 8:13 AM   #7
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Thanks TH.

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Old Feb 8, 2009, 10:17 AM   #8
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bigdawg wrote:
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...also the F/stop is as tight as the lens would allow too...so the theory that you can't focus above f/8 or so is not true with this combination.
The autofocus system uses the lens at its maximum aperture to determine the proper focus. Since the Bigma has a maximum aperture of f/4.0 to f/6.3, that is all under the f/8.0 needed by the autofocus system. And since a 1.4X TC only adds one f-stop to the maximum aperture, that would decrease the maximum aperture of the Bigma to f/5.6-f/9.0. So at its shorter focal lengths, it's still larger than the f/8.0 minimum . And since the Sigma 1.4X TC doesn't correct the lens' focal length and aperture, the camera doesn't knowthat, at longer focal lengths, the maximum aperture is f/9.0, so it doesn't know enough not to try.

The apertures used in your shots are just the settings used by the autoexposure system to obtain a proper exposure, which happensafter the autofocus system has already focused the lens.


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