Considering Sigma 300mm f/2.8 + TCs for action shooting - Nikon (D300)

I think the performance & accuracy is great with a 2xII converter attached.  Granted it's a little slower, but it is very acceptable.

7D, 120-300mm, 2xII @600mm, f6.3, 1/400s, ISO 800.

Cheers

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