To my review coverage on the Sigma 120-300mm f/2.8 DG OS HSM S is added a 300mm full aperture series from f/2.8 through f/16.
I explore the lens performance, which is very much function of many things. Useful perspective for anyone using any brand super telephoto lens.
Sigma 120-300mm f/2.8 is available at B&H Photo for about $3599 for Canon and about $3599 for Nikon. Caution as there are older versions (different design) for $2499.
White Mountains Research Center environs, White Mountains of California
Canon 5D Mark III + Sigma 120-300mm f/2.8 DG OS HSM @ f/2.8, 300mm