topic Re: Auto-Focus at f8 with 2x Teleconverter in EOS DSLR & Mirrorless Cameras

Auto-Focus at f8 with 2x Teleconverter

BillS719 — Wed, 04 Jul 2018 08:08:17 GMT

All,

Would I be able to get auto-focussing with a Sigma 100-400 f5-6.3 DG OG HSM lens plus a Sigma TC 2001 2x teleconverter at maximum zoom (ie 800 mm effectively) if this combinateion were mounted on a EOS 80d. If not, is there any EOS camera that would provide it.

Grateful for your advice.

Bill

Re: Auto-Focus at f8 with 2x Teleconverter

RobertTheFat — Wed, 04 Jul 2018 13:37:49 GMT

@BillS719 wrote:
All,

Would I be able to get auto-focussing with a Sigma 100-400 f5-6.3 DG OG HSM lens plus a Sigma TC 2001 2x teleconverter at maximum zoom (ie 800 mm effectively) if this combinateion were mounted on a EOS 80d. If not, is there any EOS camera that would provide it.

Grateful for your advice.
Bill

A 2X converter costs you two stops. If my recollection of the days of manual aperture setting is correct, that takes you to f/12.7 at the long end. I believe that's beyond the capability of any EOS camera.

Re: Auto-Focus at f8 with 2x Teleconverter

BillS719 — Wed, 04 Jul 2018 13:37:17 GMT

I have got the combination of the 100-400 zoom and a 1.4x converter to work on a EOS 100d (ie effective max aperture of about f9) by putting a small piece of tape over three of the contacts on the converter and the EOS 100d does not support AF at f8. Not surprisingly, it works best in good light but it does work.

I was wondering how a EOS body that did support Af at f8 would deal with the 2x converter?

Bill

Re: Auto-Focus at f8 with 2x Teleconverter

RobertTheFat — Wed, 04 Jul 2018 13:48:41 GMT

@BillS719 wrote:
I have got the combination of the 100-400 zoom and a 1.4x converter to work on a EOS 100d (ie effective max aperture of about f9) by putting a small piece of tape over three of the contacts on the converter and the EOS 100d does not support AF at f8. Not surprisingly, it works best in good light but it does work.

I was wondering how a EOS body that did support Af at f8 would deal with the 2x converter?
Bill

It would behave as though the conditions were 1½ stops out of spec. I suppose you'd have to tape the contacts and take your chances.

Re: Auto-Focus at f8 with 2x Teleconverter

ebiggs1 — Wed, 04 Jul 2018 14:00:21 GMT

Bill,

"I was wondering how a EOS body that did support Af at f8 would deal with the 2x converter?"

A 1DX abd 1DX Mk II can focus with f8 lenses. I might add "certain" f8 lenses. I am not sure if it works with all f8 lenses because I am not interested in doing it. The update also allows the central AF point to act as a cross-type point when working with lens/teleconverter combinations that give a maximum aperture of f8.

Re: Auto-Focus at f8 with 2x Teleconverter

ebiggs1 — Wed, 04 Jul 2018 14:06:18 GMT

Bill,

Please don't take this wrong but, IMHO, the Sigma 100-400 f5-6.3 DG OG HSM lens is not a worthy candidate for a 1Dx Mk II.

I mean it doesn't make sense to buy a $6000 dollar camera to get a $600 dollar lens combo to work. If you can get the taped contacts to work, I know several guys that do, that is how I would go at it. Some have been pretty successful at it.

Re: Auto-Focus at f8 with 2x Teleconverter

TTMartin — Wed, 04 Jul 2018 16:01:02 GMT

@BillS719 wrote:
All,

Would I be able to get auto-focussing with a Sigma 100-400 f5-6.3 DG OG HSM lens plus a Sigma TC 2001 2x teleconverter at maximum zoom (ie 800 mm effectively) if this combinateion were mounted on a EOS 80d. If not, is there any EOS camera that would provide it.

Grateful for your advice.
Bill

A 2X teleconverter with an f/6.3 lens will give you a maximum aperture of f/13 not f/8.