# 100-400 II with 1.4x Extender 6D Liveview Autofocus



## m8547 (Feb 12, 2016)

Can anyone confirm that the 100-400 II with a 1.4x extender will still autofocus in Live View on a 6D at f/8? Is it much slower than live view autofocus with a brighter lens?


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## J.R. (Feb 13, 2016)

m8547 said:


> Can anyone confirm that the 100-400 II with a 1.4x extender will still autofocus in Live View on a 6D at f/8? Is it much slower than live view autofocus with a brighter lens?



Yes it does autofocus. The focusing is slow but you can improve it by (a) using the focus limited; and (b) focusing manually to arrive at close to correct focus and then engaging the autofocus. Also, choosing a high contrast zone will help tremendously. 

Be sure that if the lens starts to hunt for focus you'll have to wait for some time to achieve correct AF.


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## degies (Mar 22, 2016)

I have a 100-400 ii and use my 2xiii extender on it and it works just fine although autofocus speed does take a hit. IQ is just fine, but at that length image blur is an issue so handholding is out. I find even tripods with gimbals is just not enough. I try and find a spot to rest the lens using a sandbag.
I have been thinking to get the 1.4 purely because of this. However I see they list it as a extender or a teleconverter.I do not quite understand the technical difference ?


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## Mikehit (Mar 23, 2016)

degies said:


> I have a 100-400 ii and use my 2xiii extender on it and it works just fine although autofocus speed does take a hit. IQ is just fine, but at that length image blur is an issue so handholding is out. I find even tripods with gimbals is just not enough. I try and find a spot to rest the lens using a sandbag.
> I have been thinking to get the 1.4 purely because of this. However I see they list it as a extender or a teleconverter.I do not quite understand the technical difference ?


I am very surprised that AF works with the 2x on the 100-400 especially at 400mm. That would take the aperture from f5.6 to f11 which is beyond the AF limit of any Canon body. Do you tape the contacts? 

Usually, the advice has been that with the image degradation of the 2xtc, it is better to use the 1.4x and crop; but when the mkiii came out quite a few reviews suggested it is the one to break that mould. 

There is no different between 'teleconverter' and (in Canon-speak) 'extender', they are the same thing.


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## nc0b (Mar 24, 2016)

As soon as my 5DS R arrives I will try my 1.4X TC III with my 100-400mm II with normal AF. I have never used live view as I shoot virtually everything handheld. I sold my 2X TC III which I briefly use with my 70-200mm f/2.8 IS II after I purchased the 400mm f/5.6. For static shots I was happy enouht with the 2X TC, but for BIF the AF was unacceptably slow.


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## [email protected] (Mar 25, 2016)

I find that the 2x + 100-400II does have a slight IQ benefit over the bare lens or over the 1.4x combination under the following conditions:
1) Still subject
2) Locked down on a stable platform
3) Using full frame body

The benefit is slight, but noticeable if all the conditions are met. Autofocus isn't terribly useful at f/11, so you'll be using liveview with magnification to manually focus in (no sweat, since you have a still subject here). The focus accuracy doing this can be exquisitely accurate due to the magnification capabilities of liveview. This is a great thing, especially in dark environments. Have been shooting woodcock in the evenings, and I can focus quite decently with liveview showing me the image at my actual ISO, effectively boosting the light versus the bare eye.

If you have a crop sensor, or moving target, or unstable platform, you'll be much, much better off with 1.4x, as the image quality degradation from those factors will exceed the IQ benefit of the one stop of magnification - at least if your experience mirrors my own tests. And, using f/8 is just so much more convenient, if for nothing other than regaining autofocus. 

I encourage you to ignore my advice and try both methods yourself, though. Please report any contradictions or confirmations.

Picture below is of a mating pair of woodcock from a couple nights ago that simply wouldn't have been acquirable without liveview manual focus with magnification, using a high ISO setting to boost visibility. This was basically night. Used 70-200 f/2.8 II and 7D2.


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## mnclayshooter (Aug 4, 2016)

degies said:


> I have a 100-400 ii and use my 2xiii extender on it and it works just fine although autofocus speed does take a hit. IQ is just fine, but at that length image blur is an issue so handholding is out. I find even tripods with gimbals is just not enough. I try and find a spot to rest the lens using a sandbag.
> I have been thinking to get the 1.4 purely because of this. However I see they list it as a extender or a teleconverter.I do not quite understand the technical difference ?



Seems like I'm the champ of reviving old threads this week, but I wanted to chime in that I have the same experience. 6D+2x or 1.4x and 100-400 (in my case its the Mk 1). 
I came to this forum looking for advice a long time ago, so I thought I would pass along any and all I can possibly give back. I found this thread by searching to see if the mk 2 lens performed notably any better. My Mk1 is pretty sharp, so from what I've gathered, I won't see much of an improvement in that regard, maybe focusing is faster and the IS is better... the corners might even be marginally sharper, but for $2k, I'll keep saving for the 300 f2.8. 

My technique to make this combo more successful (and with many other long lenses actually): manually focus to approximately the right amount to get a sharp image, then intentionally back focus it (for newcomers, what I'm describing is to de-focus the lens by focusing slightly behind whatever your subject is), then using back button focus (search google or this forum for more info), the live view will lock focus just fine in decent daylight. In a pinch, it makes for a decent 750mm-ish lens (it's not actually 400mm on the long end if you're new to the 100-400). IQ is good enough to see the veins in leaves or the subtle edges of flowers from at least 25ft or more away (the length of my side yard) and I'm not seeing any crazy fringing etc -certainly not to any extent that couldn't be corrected in post processing. Is it going to nab a bird in flight, probably not unless you're very lucky, or have tremendous manual focusing skill and steady hand holding ability. The live view screen view will take a major brightness hit if you try to shoot into the shade though, just FYI. at f11, not much light is coming through. On the 6D, the camera body compensates and brightens the image for you when you press the back-button for focus start which can aid in getting alignment/framing right. Not sure about functionality on other body models as my other one is out of commission. 

Does it work as noted above though, absolutely, it does. Is it as crisp and fast to focus as a 600mm prime - no way... is it terrible, not at all - especially if hiking or backcountry is a possibility for you. 

I think it's useful info to have on this site besides the foaming at the mouth over this or that... Some of us might actually attempt to use something like this if we know it might work and threads like this are helpful to identify specific combinations of equipment that are working for people. 

I will try to remember to post some sample photos showing the IQ achieved with my setup later tonight (provided we don't get any more severe weather today - this year has been a real crazy one for us in MN).


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