Canon 70-200 2.8L II IS: less sharp when stopped down at 200mm?

Started Feb 9, 2011 | Discussions thread
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buddhananda
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Canon 70-200 2.8L II IS: less sharp when stopped down at 200mm?
Feb 9, 2011

I am evaluating a Canon 70-200 f/2.8L II IS Zoomlens alongside a 100mm f/2.8L IS Macro and a 50mm f/1.2L.

I did newsprint shots from wide open to f/10 or f/11 on these and other lenses and stumbled into some surprises. I'm not sure what to make of these results (or whether to return the lenses). Insights appreciated.

The 70-200 was sharp at all tested apertures at 70mm and 140mm. However at 200mm it was sharp at 2.8 and then got less sharp as it was stopped down. Is this characteristic of this lens? It doesn't quite make sense, unless 200mm performance has been somehow optimized at f/2.8 in a way that leads to a tradeoff at smaller apertures.

Surprisingly, the 70-200 was sharper than the 100mm Macro. That makes me worry that the 100mm is a subpar copy, as I had read that it was sharper than the 70-200.

Despite being a new serial number series version, the 50mm 1.2L seemed unreliable in terms of focus and not very sharp compared to my 50mm 1.8 II at the same apertures. The nifty-fifty earns its name.

Any insights on the surprises (200mm losing sharpness when moving from 2.8 towards f/10; 100mm 2.8L macro being less sharp than the zoom) would be appreciated.

Thank you,
-Ananda

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