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A Cautionary Tale, Canon 300mm f2.8 IS II USM

Feb 8, 2012
Indialantic, Fl
Real Name
I recently purchased the above mentioned lens after having great results with a Canon 200mm f2.0.
Both have been attached with a Metabones adapter and the 200 could handle "medium" continuous
focus quite well. The 300 II on the other hand only focuses (in CF) at low speeds. Even then it is hit
or miss.
For single shot the lens is amazing and I am a bokeh junkie. So now I am entertaining the idea of
going back to a Canon body for this lens. My guess is that I could have purchased an EOS 300mm
IS USM for less money and had better results.

Meanwhile.... single shot on the A7RIII.......




Dan Euritt

TalkEmount Veteran
Jan 11, 2014
A7-series bodies will be limited to about 3fps af-c with Canon brand glass, you'd have to step up to the a9 to get 10fps af-c in that situation. Maybe try renting an a9 and mc-11, see how it all compares with that lens?

It works like that because most adapters emulate the laea3 a-mount adapter, which puts artificial limits on a7-series af-c performance.

The only caveat I can think of is that there are two different modes on the Metabones adapter, if one mode makes the camera think that it's a native e-mount lens, it shouldn't have any limits. I don't own one tho, so I've never tried it: https://www.metabones.com/article/of/green-power-save-mode
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