*UPDATE 2*
Another suggestion from a man who knows everything about lenses. He thinks it's a “28-300 with filter barrel removed”.
*UPDATE*
It seems most people think it's the Sony 70-200, though the body does look like a Canon.
I'm not sure
Below is an image posted on the Google Plus account of Peter Norvig. In the low resolution image, a lens that I don't recognize is being used. I have compared it to the 28-300L, 100-400L and 70-200L and it doesn't match up with any of them.
Says Peter
“For Canon fans, you might find this exciting. A photographer was using this lens. I assert that the black stripes of the focus and zoom rings are the wrong width and placement to be either the 70-200 or the 100-400; therefore I speculate this is a prototype of the long-rumored 100-400 II.”
What do you guys and gals think?
Source: Peter Norvig G+ thanks to John
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