Originally posted by cajuncutter The flare is that bad?
Here's an example of the issue with a K-3 and the HSM II (minus the hood adapter), circa 2014:
It's normally only a noticeable issue if you have a strong light source (eg a stadium or stage light) coming into the lens directly.
Flare and ghosting is sometimes made more prominent when you use a FF lens on APS-C because the stock FF lens hood as supplied is not optimized for the narrower field of view of APS-C. So by extending the lens hood out a bit, it restricts stray light coming into the lens more effectively.
Sigma have different models of 'lens hood adapters' for full-frame lenses like their 105 & 150mm macros for people who want to use those lenses on APS-C, so it's not something they only offer for their 70-200's.