05-13-2016, 07:59 PM
This is very much a macro lens first, and a general purpose prime second. Most macro users don't care much about using the lens wide open as lack of depth of field is often a problem. DSLR macro lenses tended to be f/2.8 as that was needed to maintain phase AF, as they were effective f/5.6 at 1x magnification (not sure how the 180mm f/3.5L gets around that). Contrast AF wouldn't have that limitation, although the possible hit to any phase AF on sensor might result in slower AF.
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.