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teleconverter 1.4x iii autofocus problem

jsfarnsw
Contributor

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?

2 ACCEPTED SOLUTIONS


@jsfarnsw wrote:

Thanks everyone.  I did not realize the AF systems required that much light to work properly. 


AF needs adequate light to work reasonably fast and reliably.

 

Do an internet search about teleconverters and taping up some of the contacts. This "fools" the camera into not realizing the converter is there, so that it will still try to AF the lens. Just don't expect focus to perform very well. It will be slower and in lower light situations or with low contrast subjects it may hunt a lot and even fail to achieve focus. There's a reason Canon sets a limit and turns it off, when a lens/teleconverter combo exceeds the rated AF capabilities.

 

You'll have to find a website where someone illustrates which pins to tape up. I haven't done the tape trick myself... I simpy don't bother with TCs on lenses where it would exceed the light levels, or in a few cases I just manually focus (500/4 with a 2X on it, for example).

 

7D Mark II (not the original one), 5D Mark III (not the II or original), all 1-series (film and digital) and the EOS-3 film cameras are "f8 capable", meaning that they can still AF (mostly with one center AF point only... 5DIII can use a small group of points in the center I believe) when a lens + TC makes for an f8 or larger aperture. All other Canon cameras, including 70D are "f5.6 capable".

 

The 100-400mm is f4.5-5.6 already... so adding even a weaker 1.4X, makes for an f6.3-f8 combo that exceeds your camera's design capabilities. But some folks manage to make it work to a limited extent with a few small, carefully placed pieces of Scotch tape!

 

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.

 

***********


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 

View solution in original post

What a surprise to get notifications that someone was resurrecting this zombie thread!

 

The fix for me was to sell my EOS 70D and purchased an 80D, which will autofocus at f/8.  I have since added a 90D to my kit and I've replaced the EF 100-400mm with a 400mm f/4 DO. The only thing I kept from those days was the 1.4x teleconverter. Amazing how equipment upgrades can solve an autofocus problem. 

View solution in original post

35 REPLIES 35


@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. 


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

Bob
Philadelphia, Pennsylvania USA

???????????

EB
EOS 1DX and 1D Mk IV and less lenses then before!

jrhoffman75
Legend
Legend
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.
John Hoffman
Conway, NH

1D X Mark III, Many lenses, Pixma PRO-100, Pixma TR8620a, LR Classic

jrhoffman75
Legend
Legend
The Dual Pixel technology works in Live View only. There is no aperture limit in Live View.
John Hoffman
Conway, NH

1D X Mark III, Many lenses, Pixma PRO-100, Pixma TR8620a, LR Classic

Thebellanger
Apprentice
Hey folks how is everyone? I recently purchased an older Canon 500 mm f 4.5 zoom lens. I tried the 1.4 converter mk 3 and it did not autofocus on my 70D or my 5 D3 very disappointing any suggestions?

See this

 

IMG_0737.PNG

 

Do do your cameras have an f/5.6 autofocus limit. 

John Hoffman
Conway, NH

1D X Mark III, Many lenses, Pixma PRO-100, Pixma TR8620a, LR Classic


@Thebellanger wrote:
Hey folks how is everyone? I recently purchased an older Canon 500 mm f 4.5 zoom lens. I tried the 1.4 converter mk 3 and it did not autofocus on my 70D or my 5 D3 very disappointing any suggestions?

You say it's a zoom lens, but you don't specify its focal range. Is it a lens that's 500mm at the long end, but f/4.5 at the wide end? If so, and if it isn't a "constant aperture" lens (i.e., one whose maximum aperture is the same throughout its zoom range), it will be slower than f/4.5 anywhere but at the wide end. But a 1.4 teleconverter subtracts a full stop from a lens's maximum aperture throughout its zoom range. IOW, it turns f/4.5 into f/6.3, and only a few high-end cameras can autofocus at above f/6.3. Which means that at best your 70D will autofocus only at the wide end of the lens's range. Your 5D3 can do a bit better; but unless your lens is f/5.6 or better at the long end, even it won't be able to autofocus over the full range. So you're probably going to be limited to manual focusing most of the time.

Bob
Philadelphia, Pennsylvania USA

Yet another reason why t-cons are a bad idea at best.

EB
EOS 1DX and 1D Mk IV and less lenses then before!

"Yet another reason why t-cons are a bad idea at best."

 

Not true - they can serve a useful purpose. One just needs to read the appropriate documentation and be aware of any limitations.

John Hoffman
Conway, NH

1D X Mark III, Many lenses, Pixma PRO-100, Pixma TR8620a, LR Classic

Ultimately, I sold my 70d and purchased an EOS 80d.  Problem solved. 


@Thebellanger wrote:
Hey folks how is everyone? I recently purchased an older Canon 500 mm f 4.5 zoom lens. I tried the 1.4 converter mk 3 and it did not autofocus on my 70D or my 5 D3 very disappointing any suggestions?

 

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