For all you experienced C100 users -- what's the highest useable ISO you'd use on a shoot while still retaining what you would consider "quality" professional results? I'm using a Mark1, shooting in C-log. Trying to stick with 850 ISO as much as possible, but it'd be nice to know how much leeway I really have. I expect I'll be doing fairly heavy grading. Recording ProRes onto a Ninja2. Thanks!