Story is important blah blah blah. Yeah, everything these people are saying is true. BUT I hate asking a question and people basically refuse to answer you because they want to teach you a lesson. Ugh.
If you're not really interested in slow motion, the Blackmagic Pocket cam is the best deal out there in that price bracket. The image is incredible out of that little guy. BUT, you will also end up spending more than $500 to get it working. You will need a better battery solution; don't bother with the ones that go in the camera; they die so fast they're almost useless. My friend on a budget just uses some Anker portable phone batteries and an adapter to plug into the DC port on the black magic camera. Powers the thing for hours--only issue is using it with a Glidecam; then you do need the dumb little internal batteries... Anyway, you'll also need some hefty, fast SD cards--they're pretty cheap, but still. AND you'll need a lens adapter for your lenses. I recommend a Speedbooster; it will help you save on glass, allowing you to use the lenses you have. All together (if you use phone batteries to power the camera), you're looking at $1100 to get the camera running?
Totally worth it though!
Nah, I doubt this camera will rent. Definitely more aimed at owner-ops. Anyone that has budgets to rent cameras could easily get an Epic for cheap enough.
Sorry, but I have to disagree again. The Samyangs are terrible. I meant to say that earlier, but I forgot. Please don't get Samyangs. The contrast is terrible, which is why they always look so soft. And the build quality is equally as bad.
Ignore what Alex says about Crop Mode. Yes, it does raise the noise floor, but I found I could still shoot up to ISO 12,800 with useable results. One stop less than FF mode (which I only found to be useable up to 25,600). When I had that camera, I shot almost everything in crop mode, since it dramatically reduced the rolling shutter.
I would personally stay away from Canon's zooms. I don't consider any of them to be worth the price for video. The Tamron is definitely better value, and it might work as a stand-alone lens, but it also has a backward focus ring--not a big deal if it's your only lens, but as your collection expands, you will find yourself hating it (or hating all your newer lenses!).
My personal recommendation is a Contax Zeiss 35-70mm f3.4 for $300-400. I used it for a little while on the A7s, and it's awesome. It gives you a nice wide in FF mode, but you can get in pretty tight in APS-C mode as well. And the coatings on that lens are beautiful! Plus, at the 35mm end, you can use it in macro mode. It really has everything you could need. Yes, it is a little slow (only f3.4), but you can always boost the ISO on your camera a bit to compensate.
The only thing you'll be missing out on is a wide aperture for those really shallow depth of field shots. f3.4 gets you there most of the time, but sometimes you just need it to be shallower. That's why I recommend getting a Contax Zeiss 50mm 1.4 for $300. Incredible all-around lens.
Those lenses are Contax/Yashica mount; you can get a C/Y to E-mount metabones adapter for $100 (don't go for a cheap brand!). So, for about $800, you're getting a great zoom and a great prime, with the nice Zeiss coatings, that covers you from 35mm in full frame to the equivalent of 105mm in crop frame (70mm x 1.6).
Really, I can't recommend Contax Zeiss lenses enough.
I buy from eBay all the time. You can get some killer deals on there that you won't find elsewhere. Guy's advice is spot on. Also, I beware of buying internationally because if there is a problem with the gear, it's much more costly/difficult to return overseas.
Forgot to mention, I don't think that 4K is enough to tip the scales in favor of the A7s II. It will still be just as frustrating to operate. I would much rather have ease of use than 4K. You would be surprised the difference it makes under the pressure of shooting.