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Old Feb 17, 2007, 11:20 PM   #1
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I have the 30D and am using the 70-200L IS USM...which extender is the best for this gear. I am using a vivitar series 1 now and it's probably not the best extender out there. I have to manually focus my shots using this converter...would that be the same situation for the canon converters...Thanks, Donna
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Old Feb 18, 2007, 8:49 AM   #2
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Is that an 70-200L IS USM f/4?
-> in which case @ f/8 any 2x teleconvertr will have problem focusing...
(You need an f/2.8 for a 2x to become f/5.6 to still be able to AF)

A 1.4x of any brand should work juste fine :idea:
i.e. an f/4 will become f/5.6 with with the lost of 1-stop...
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Old Feb 18, 2007, 8:50 AM   #3
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Yes F/4...
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Old Feb 18, 2007, 8:55 AM   #4
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D.Ann wrote:
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Yes F/4...
The other option is to upgrade the camera to a 1 series :lol: :-) :G
-> They'll focus to F/8 - Just kidding you but that's true... (my 500 f/4 focuses fine with a 2x on a 1D Mrk II @ f/8 )
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Old Feb 18, 2007, 10:33 AM   #5
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WEll, that lens is not in my future for now... I have spent a ton on my "hobby" as it is...but thanks. Donna
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Old Feb 19, 2007, 10:41 AM   #6
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is the vivtar TC a 2X or 1.4X? As NHL saidif it's a 2X it won't autofocus with your lens. if it's a 1.4X then it may be a problem with either camera or lens if it doesn't autifocus. somef/2.8 lenseswill not autofocus with a 2x TC even though they are only f/5.6 with the TC. The sigma 150mm macro is one of those lenses.

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Old Feb 19, 2007, 12:51 PM   #7
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It is a 2x. I am thinking of buying the 1.4x from canon. Donna
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Old Feb 19, 2007, 2:03 PM   #8
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Donna, that's what I figured but wasn't mentioned.

NHL, this a bit of a sidebar but, I want a 1 series Canon. I tried stacking a sigma 2X & 1.4X on my 500mm, I taped the 3 pins on the 2X TC but the camera still saw it and recorded f/8 so no autofocus. Maybe I taped the wrong 3 pins?

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Old Feb 19, 2007, 11:28 PM   #9
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djb wrote:
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NHL, this a bit of a sidebar but, I want a 1 series Canon. I tried stacking a sigma 2X & 1.4X on my 500mm, I taped the 3 pins on the 2X TC but the camera still saw it and recorded f/8 so no autofocus. Maybe I taped the wrong 3 pins?
2x plus 1.4x is f/11 which do not carry enough differential data from the subject for the phase detector in the camera to work from - I also notice stacking two TC do not produce the exact aperture and the combo does not AF on my 1D mrkII either
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Old Feb 19, 2007, 11:37 PM   #10
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something strange with my 5D. I stacked the 2x over th 1.4x and the camera read only 5.6(lens used ins 120-300). I was expecting it to stop down three stops. But it stopped to 5.6 and the camera auto focussed well.

And i can see the lens getting even closer with the combination so the effective focul length is around 720.

Not sure why. The 2x is a DG version while the 1x is the previous version.

Am i reading it wrong. the exif shows 600mm only though
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