1.4 TC

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4 Nov 2012 - 1:35 AM

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StrayCat (e2 Member)

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4 Nov 2012 - 1:41 AM

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Better confirm it, but I think the MK II and III require newer, very expensive lenses to be of any additional benefit. Also, I don't think you will get auto-focus with TC on that lens. I could be wrong, so check into it thoroughly.

Denny

colin beeley (e2 Member)

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4 Nov 2012 - 9:09 AM

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it will give you f/8.0, & i think you will not have auto focus on a 7D.you would on a 1D camera though.

tomcat (e2 Member)

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4 Nov 2012 - 11:06 AM

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Quote: it will give you f/8.0, & i think you will not have auto focus on a 7D.you would on a 1D camera though.

I use a Sigma 1.4x occasionally with my 400mm 5.6 and 1d Mk III and as Colin states you have f/8

ringyneck (e2 Member)

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4 Nov 2012 - 12:38 PM

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Thanks again everyone....Blimey I cannot believe how kind people are....Thanks louise for the offer...If we meet up again and you have it I wouldn't mind - just to see what effect it would have.Mind you I think the man focus would be a pain ...old eyes you know...

I find it amazing that own brand TC's loose AF on lenses that are far from the budget range.....
Keith

chris.maddock

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4 Nov 2012 - 4:56 PM

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Quote: I find it amazing that own brand TC's loose AF on lenses that are far from the budget range.....


It's not the lens that counts - it's the minimum aperture in the camera's specification, f8 on 1D/1DS cameras, f5.6 on the others. The TC disables the AF because the combination of TC and lens takes it outside the camera spec so Canon cannot guarantee reliable AF.

The reason your Bigma didn't lose AF is that Sigma lenses "lie" to the camera, only reporting f5.6 to the AF system.

That said, depending on the lens, it can be possible to fool the camera by taping over some contacts on the extender as per the first tip below;
http://www.fredmiranda.com/TipsPage/

I say "depending on the lens" because the contacts concerned appear to do different things with different lenses - for example, it works a treat with a 1.4x extender on the 100-400/f5.6 L but was absolutely useless on my 70-200/f4 (original version). It may also only work with Canon extenders or, maybe, only Mk1 Canon extenders.

chris.maddock

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4 Nov 2012 - 5:25 PM

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Quote: Blimey it's more of a minefield than i thought it would be...thanks for all the info.


Afraid so.

What you could try would be to apply tape to the back of your 400/f5.6 (reversing the view in the link I posted) and try it and your 7D with a 1.4x extender (either from someone you know who has one or a local shop) to see if it works. If it does you have your answer - well, actually you'd also have it if it doesn't

NeilS (e2 Member)

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5 Nov 2012 - 5:41 PM

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Can't speak for the 400l, but Kenko DGX converters also relay incorrect info back allowing AF at f8 and beyond, I have the 70-300L and that will physically only take a Kenko and it autofocuses with a 50D even with a 2x

If you google kenko 1.4 DGX and 400 L you should find the answer, although I would pay some attention to the performace achieved by others with a 7D body, as both AF speed/accuracy and IQ can take a hit

Basically a 5.6 min aperture moves to F8 with a 1.4 tc ie one stop, and two stops to F11 with a 2x tc

I was so disappointed with my Canon 2x mark 2 that I sold it, after aquiring a Kenko and I still use the Kenko DGX 2x on my three long lenses