I'll be the first to say I am learning. I am not a shooter. I am a VFX guy.
I picked up a T2i a few months ago , went out and shot my *ss off and loved it. Never had any issues with noise or such.
I got my GH4 + Mbones Speedbooster-Nikon adapter and a nice Nikkor lens + Tokina so I am shooting roughly S35 size...etc.
It's noisy. It's noisy in the blacks in a nicely lit daylight room. The white walls dance with noise.
I'm blown away that you cannot unbox this in a nicely lit office, shoot some footage ISO200 at 0exposure and not see noise!
I have read through many, many,many threads regarding settings (millers)....comparisons, profiles and such. I have seen low light tests (MkIII kills the GH4 in Blooms...)....I have seen AMAZING noise free footage shot "out of the box" indoors! I have seen exteriors at night with noise....to be expected.
Ive shot wide open at 200ISO and gotten noise.
I've shot at 2-3 and upped the ISO to 1600 exposing to the right of zero and gotten noise.
So far, indoors...in any settings I get noise.
Outside I am OK as long as I am shooting something bright....the minute I pan past any shadows or anything slightly 'dark' it's full of noise.
Indoors, mid-day on a nice sunny day with plenty of natural light I absolutely cannot get an image I even find acceptable. And nothing close to an image that makes me say "wow".
I have posted a .MOV right from the camera...this was ISO 800 I believe, shot wide open on the Tokina 11-16. Natural light. Shutter speed at 50. Exposed at around 0 - +1