09-11-2015 01:59 PM
I was taught the same thing, but that was before image stabilization came to lenses. My real life testing was done to quantify the best combination of speed, aperture, and ISO for the 100-400 Mark II lens on a 70D camera both with and without the 2x extender. The new II lens has amazing image stabilization which will allow you to shoot at the slower speeds required for f11 and lower ISOs.
Focus for both the old and new 100-400 lens with the extender will work only in "live view" using a 70D camera, but it works well. If you like to view through the lens when you take photos, focus in live view first, switch to manual focus, turn live view off and then compose through the viewfinder. Just remember not to touch the focus ring.
I haven't has any problems with normal focus at f8. It dose have a narrow depth of field so if you focus but holding the shutter halfway down and then wait until the subject is closer you could have a problem. There are some AI focus settings that could help.
I can't speak to how this works on a 6D, I only have the 70D
12-03-2015 12:10 AM
Yes, Live View focusing with the 70d is pretty unique. I have the 7d MkII and go to the 70d to do moon photos or super distant shots with a 300mm f4 L and the 2x. I'll have to try the 100-400mm MkII soon as I just sold the 300mm to move to the new 100-400mm. I rented it about six months ago but didn't try any teleconverter on it then.
01-04-2016 01:37 PM
Man I glad I read this, I have a Canon 70D I was using with a new 1 to 400 mm EF lens along with a EF 2X loll extender, the Canon tech told me I would have to manually focus with it, so I have been with some real good results most of the time, I tried your suggestion in live mode & the auto focus worked great! This will be a valuable option when I need it, I bought a new 6 D full frame to use wit the lens, extender combo recently as well, works well but I wish it would auto focus like my 70 D does as I use it all the time for wildlife, the auto focus would come in handy, though I'm getting a lot better manually focusing & you can get good results if a person gets used to using the setup, Many Thanks for the valuable info. Jesse.
10-13-2017 02:41 PM
I have a Canon 7D MkII that I cannot set up to allow AF with the 100-400 + 2x extender. I have tried all the setings mentioned in several articles. I realize there a very few applications for this , but want to be able to access the AF with the extender. Any better ideas other than what I have tried? (menu 4- select AF area, tried with no luck at all modes)
10-13-2017 02:53 PM
The most you should be able to use with that camera (with ANY camera, actually) is a 1.4x extender.
This has to do with how phase-detect auto-focus systems work. They need light coming to the focus sensor from different angles (normally not a problem with a wide-open aperture) but as you narrow the aperture, the opening is no longer large enough for the light to arrive from angles far enough apart to work.
Most DSLRs can only have working auto-focus on lenses of f/5.6 or less ... but Canon's newer cameras (such as your 7D Mark II) offer support for f/8.
When you use an extender, you must multiply BOTH the focal LENGTH and the focal RATIO by the extender multiplier (e.g. either 1.4 or 2.0).
So the 100-400 f/4-5/6L becomes a 200-800 f/8-11 (and it's only f/8 at the 200 end ... the moment you zoom in even a tiny bit the aperture is too narrow.
You can still manually focus ... you just can't use auto-focus.
If you used a 1.4x extender then the 100-400 f/4-5.6 becomes a 140-560mm f/5.6-8 lens and that WILL work becuase the wide-open apertures are f/8 or lower for every focal length available.
The 2x extender must not be used with any with a focal ratio higher than f/4.
Also note that there is a slow-down in the speed of AF (always) whenever you use an extender. This is intentional (normal).
10-13-2017 02:59 PM
10-13-2017 03:20 PM
The AF works on my 70D in live mode with the 2Xextender, otherwise its manual focus only, the edges are soft when you have the zoom wide open, bad in low light situations, not a great combination in my view.
10-13-2017 03:22 PM
Thank you for explaining that so I can understand it. What you say makes sense. But according to some users and distributors
this camera can work with the extender and lens in autofocus, but ZI am unable to make it happen. I'll still use it on occasion anyway, but am frustrated that I can not acquire AF no matter how I set it.?
It can work with a 1.4x extender (which would take that lens to f/8 at the long end of the zoom range) ... just not with the 2x extender (which takes it to f/11 at the long end of the zoom range.)
BTW, there are even limits when using f/8... you can't just use any AF point -- it supports the center point. I think it can "borrow" the immediately adjacent points when using AF point expansion mode ... but that's it.