My Christmas present from my husband !!!
I've been playing with it for the past 20 minutes or so and I'm going to love it!
It reduces the lens's f/stop from 2.8 to 4.0 - shouldn't be a problem most of the time.
Heads up, though: It is NOT compatible with the 12-40mm PRO lens, but works very well with the 40-150mm PRO lens.
According to PC Mag it will also be compatible with the soon-to-be-released 300mm PRO lens.
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