100-400 + Kenko TC's - Weird behavior ERR 01 & Others

Started Feb 27, 2014 | Discussions thread
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100-400 + Kenko TC's - Weird behavior ERR 01 & Others
Feb 27, 2014

So , I'm wondering if anyone has this combo, or another combo and has noticed this

If I mount the Kenko Pro 300 DGX 1.4 or 2x to my 100-400, on my 70D, and have IS + Ai Servo + High Speed continuous turned on, AND my shutter speed over sync (1/250) I get an ERR 01 after 2-3 frames.

If I put on low speed continuous shooting + AI Servo + IS, with shutter speed over sync I get jumpy IS and loud clunking noises

If I put on single shot + AI Servo + IS , with shutter speed over sync, I get smooth perfect quiet (for this lens anyway) IS and can hit the shutter as fast as I want with no issue

By jumpy IS I mean that every time I hit the shutter button, the frame jumps up or down a LOT, like it's significantly shifting the IS elements out of whack.  The shots still come out stabilized and sharp, but it's concerning to say the least as far as the operation of the lens goes.

I'm just wondering if anyone else has experienced this with this lens, or any other big IS lenses - it almost seems like there isn't enough bandwidth in the communication through this teleconverter to handle that many operations going to the lens at once, based on how the behavior improves steadily as I take things out of the equation (take out faster than sync speed, AI Servo, IS , or continuous shooting, and the lens starts to get back to normal operation as you take one or more pieces away from the equation)

It's not a huge deal because I can just turn off continous shutter and it works great, but it just seems odd.  I almost want to try the canon TC's with tape to get AF, but I really don't feel like spending the kind of money Canon asks for them, especially when the IQ of the Kenko's is pretty much just as good.

Canon EOS 70D
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