I finally brought the Sigma 150-500. And took it whale watching within 30 minutes of purchasing the lens, not a good idea. Firstly, a great lens. The problem, holding this lens and body and standing on the observation deck with minimal swirls of 1 metre or 3.5 feet. Majority of pictures were soft or missed the whale while trying my best not to fall on my ass or over the rail. Plan is to take this lens out to the park this week with a tripod.