Over the years we've gotten spoiled by all the advancing abilities of cameras these days. One of those abilities is ever increasing sensitivity to light, meaning higher and higher usable ISO ranges. In this comparison, we'll take a look at 3 cameras which came along at 3 different stages of advancement in sensor & processing technology.
Up first we have the Sony Ex1, the very first professional full HD camera with a sensor larger than a 1/3" for under 10 grand. a big leap forward in sensitivity and IQ. I distinctly recall being overly pleased with how little light it needed to get the job done. It helped that it was paired with a lens which held F1.9 throughout its zoom range.
Then we had the DSLRs come around, and the 5D at the head. Again, a leap, and i would constantly look at how little light the 5D needed and thinking about how much less wattage i could use in lighting. Was it noisy at iso 3200? Heck yes, but impressively clean when looking at how just a few years back, anything over iso 800 on my canon 30d stills only camera would start to look a noisy mess.
And then the Canon C100, or any of the canon C series cameras, or the Sony FS series, etc... It's a new level of light sensitivity, where i can say with a strait face that i like the iso 20,000 on the C100 more than i like the 5D at iso 3200. It's a bit unfair for the DSLRs really, especially the first generation of video dslrs, because they are photo cameras that happen to shoot video, not the other way around. You can only expect a piece of equipment to do what it was designed for, anything on top of that is icing, and icing can run thin (someone teach me metaphors, i clearly slept through english class)
The results are not surprising, each generation is a leap, but to me the biggest leap is the C100, it's just mind boggling how good it looks with absurdly little light. I need to mention again that it doesn't mean that you don't need lights, because that would mean that you're being lazy and not designing your lighting. It allows you to use vastly less power. Or in certain situations it gives you the flexibility to get more DOF. At the time of this writing i just shot a reality pilot in which i was the only camera, and the producer basically having me whip the camera this way and that to catch 5 different people's reactions. I valued every extra bit of DOF i could get, and i was playing the hyperfocal game. i averaged iso 3200-6400, and F5.6-11. Yes i know, you don't like it unless it's so narrow a DOF that only a single blade of grass is in focus, but listen here, shallow DOF has its place, it's not a storytelling device and can serve zero purpose at all if used poorly. But i'll stop myself there before full rant mode kicks in.