I think I'm having issue with my Canon 70D in low light situation.
Comparing to other people who have done low light comparison on 70D on youtube. Some of them have ISO set to as high as 1600 in low light, and it seems reasonably fine.
I shot my video with 50mm lens at 1080p 30fps, f1.8 and ISO 250
I am having significantly and noticeable noise in my test video. And even some ugly 'lines' in the top right part of the video.
Why is my footage like that even when my ISO is relatively very low comparing to others using 1600 and still be fine.
The video might be compressed and may be hard to see, but it looks pretty bad original.
Frankly, I'm not seeing any issues with the video. I don't see any lines. The image is really underexposed, though. Even low-light tests still require enough light to use the camera and lens the way they're supposed to be. Even the Zacuto low-light tests had a lot more light than they were letting on (in a professionally-lit environment I'll add). I think you are trying to use no-light (or as little as possible) which isn't a good way to test your camera. For one, even with a f1.8 50mm, you want to have it in the f4 range and, ideally, starting in the f8 range (if you can't see anything, add light) since f8-11 is the range most lenses are designed (wide open is a last resort). Consider a cine lens - you can rent from places like Borrowlenses for very little $. I've seen a lot of complaints about the Canon 70D and it's lowlight, but in nearly every case, the environment is at almost NO light (no camera works well in no light). Despite this, every camera that captures video needs lots of light to work correctly and even more to work well. You aren't doing your camera any good with a minimal exposure - you aren't testing anything at that point because the camera has no range on the low end - you're just looking for the lowest limit not a range. If you want a good lowlight performer for video, consider a video camera instead of a DSLR.