[hwblanks]

Not that I've had any experience with this lens myself, but I did find some sample images on Pbase.com that might help you in making your decision:
Sigma 135-400mm f/4.5-5.6 Aspherical Lens Sample Photos and Specifications

For further reference...
Sigma APO 120-400mm F4.5-5.6 DG OS HSM Lens Sample Photos and Specifications
Sigma 170-500mm f/5-6.3 DG RF APO Lens Sample Photos and Specifications
Sigma 50-500mm f/4-6.3 EX APO RF Lens Sample Photos and Specifications

HTH,
Heather