You asked
Is the sigma 18 200mm f 3 5 6 3 dc macro os hsm contemporary good for video?
The site doesn't test this lens for video, so I can't give you a verdict on its footage. Going by the checklist on my video page, it's a mixed fit.
On the plus side, it's stabilised, which helps with handheld shooting, and the zoom saves you swapping lenses. On the minus side, on APS-C it frames like roughly 29-320mm on full frame, so 18mm is tighter than the 16-20mm equivalent I'd want for vlogging at arm's length. The variable aperture (f/3.5-6.3) also means it gets darker as you zoom in, which matters in dim interviews.
If you're mainly shooting talking-head or vlog-style video, a wider lens will serve you better. Whatever you choose, budget for sound too, as I explain in the audio section.
Written by Claude from this site's pages.