Sigma 400mm f/5.6 APO (manual focus) + 2x TC: my review.: Pentax SLR Talk Forum: Digital Photography Review
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Sigma / Carl Zeiss Jena (AF and MF) IF MC multic 400mm F5.6 Lens Reviews - Sigma Lenses - Pentax Lens Review Database
Sigma / Carl Zeiss Jena (AF and MF) IF MC multic 400mm F5.6 Lens Reviews - Sigma Lenses - Pentax Lens Review Database
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Amazon.com : Sigma 120-400mm f/4.5-5.6 AF APO DG OS HSM Telephoto Zoom Lens for Canon Digital SLR Cameras : Digital Slr Camera Lenses : Electronics
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