I have tried the 135L with Sigma EX DG 1.4x and 2x extenders, and the result was horrific. There was a glow everywhere and I would consider that unusable. I'm hoping the Canon ones would actually work better but I don't have access to one to try myself so far. It is listed as compatible with extenders. Maybe the extreme speed of this lens is too much for Sigma's offerings.
The overall AF performance with extenders is down to two parts, the body and the lens. At least the body should still retain the ability to focus using any f/2.8 sensitive points with a 1.4x extender. I don't recall noticing any difference in AF speed with the 7D when I tried it.
The overall AF performance with extenders is down to two parts, the body and the lens. At least the body should still retain the ability to focus using any f/2.8 sensitive points with a 1.4x extender. I don't recall noticing any difference in AF speed with the 7D when I tried it.
<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.