teleconverter 1.4x iii autofocus problem

[jsfarnsw]

my 100-400 ii won't autofocus with a 1.4x iii on an EOS 70D.  When I install the teleconverter, the camera automatically switches from AF Servo to M Focus.  

Solutions?

[amfoto1]

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@RobertTheFat wrote:

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@ebiggs1 wrote:

"Note: There are a few third party lenses that are f6.3 even without any TC, yet still AF... probably by similarly "fooling" the camera."

And you are correct.  The big 150-600mm Tamron and Sigam both report f5 to the camera.  Even though it is at 600mm and f6.3.  I hear rumors that Canon is testing a 600mm f6.3 prime.  It will interesting to see how they handle it.

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Does it matter? Anyone who can afford one will already have at least one of the f/8-capable cameras. Of course any extender will throw it over the limit, but who needs an extender with a 600mm lens?

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I don't know about that... We're discussing a $2200 Canon 100-400 Mk II here.

The Sigma "C" 150-600 and Tamron 150-600mm are both very affordable for such long telephotos. Under $1100 US.

Even the Sigma "S" 150-600 isn't too bad at $2000. That's pretty close to the price of the 100-400mm being discussed here, too. 

Any of those seem like bargains compared to the EF 200-400/4 with built-in, matched 1.4X ($11,000)  or an EF 600/4 Mark II ($11,500).

But I agree with you... on a crop sensor camera a 600mm lens is an extremely long focal length. Adding a 1.4X to it would be sorta nuts. Shooting through a lot of atmosphere can begin to have some effects even at 600mm. Even 400mm is a whole lot of lens on an APS-C camera.

Might be better to try to get a wee bit closer to the subject, instead.

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & EXPOSUREMANAGER 

[ebiggs1]

"Might be better to try to get a wee bit closer to the subject, instead."

Of course this is always the best solution.

"I don't know about that... We're discussing a $2200 Canon 100-400 Mk II here."

You don't know about, what?

[amfoto1]

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@ebiggs1 wrote:

"I don't know about that... We're discussing a $2200 Canon 100-400 Mk II here."

You don't know about, what?

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"Anyone who can afford one will already have at least one of the f/8-capable cameras..."

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & EXPOSUREMANAGER 

[ebiggs1]

Yeah, I guess, likely.

[jsfarnsw]

I stand as a case in point.  I own one camera, an EOS 70D, and one lens, the 100-400mm ii.  And a 1.4x iii converter. 

[RobertTheFat]

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@jsfarnsw wrote:

I stand as a case in point.  I own one camera, an EOS 70D, and one lens, the 100-400mm ii.  And a 1.4x iii converter. 

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Yeah, but you didn't pay $11,500 for that lens. If you had, I daresay the 70D wouldn't be your only camera.

[ebiggs1]

???????????

[jsfarnsw]

Okay, I've tried the tape trick.  True, it's slower and less sharp than the normal AF without the TC.  However, it gets you close enough to manual focus from there quickly.  This probably means fewer missed shots when photographing wildlife. 

I'm not convinced that there's a technological reason that the 70D can't AF down to F8.  The sensor may actually be better equipped to handle this than other "pro" cameras.  Is Canon trying to sell "pro" camera bodies by intentionally disabling more capable "amateur" bodies?

Time for a firmware update.  Shame on Canon that we have to use scotch tape to do wat they are too timid to do in firmware. 

[jrhoffman75]

There's probably some of paragraph 2 going on.

But, all the lens contact does is send the aperture value. All of what you observed in paragraph 1 would exist. That's probably not an acceptable level of performance for a autofocus camera.

The instruction manual for the 100-400 clearly states it won't autofocus with teleconverters, but gives a footnote for some cameras. You did receive the lens capability you paid for.

[ebiggs1]

"Shame on Canon that we have to use scotch tape to do wat they are too timid to do in firmware."

How can you say that when you said ...

"... it's slower and less sharp than the normal AF without the TC."

Do you really think Canon would advertize, "Our cameras focus slower but get you close to AF so you can finish in MF!"

"Plus it's almost sharp!"

You did get what you bought.  The tape is a trick to fool the camera to work under conditions it was not designed to.