Hi so I have a question.... I shoot wildlife and my situation is that I normally film with Canon long lenses like the 500 or 100-400 stuff like that. I really like using Image stabilisation all the time as it helps the steadiness especially in windy moments. The problem is, I'm thinking of switching to a long Sigma lens (150-600) and after tests, I noticed that the IS doesn't work on the epic but it does on everything else. The camera mounts the same so why won't 3rd party lenses work with epic? Not sure how it makes sense? Is there something i'm missing or maybe an adapter I should get?