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).