Lighting/Lens Tips for DSLR Noisy Video
An APC-C sensor size has a diagonal that's 1.6x smaller than FF35 (such as EOS 5d), which means that for a given field of view it behaves as if there's about 1.5 stops more depth of field.  Or, seen another way, if you are shooting indoors, you might use a 35mm lens on a FF35 camera and a 22mm lens on an APS-C camera, in which case the 22mm lens has about the same depth of field as if you stopped down the 35mm lens an additional 1.5 stops.  So your 18mm f3.5 gives you the depth of field similar to a 28mm shooting at f5.6 (which is pretty deep) and a 55mm shooting at 5.6 has a similar depth of field as an 85mm shooting at f9 (which is still pretty deep).  If you rack focus between the back of the room and an object 8" in front of the camera, you will see the rack focus effect, but if you rack focus between 6' and 8', the effect will be minimal.

Cameras such as the SONY A7 are low-light wizards, but nothing else does low-light like that.  And shooting with ambient lighting is a recipe for boring, flat-looking video footage that looks amateur.  Do study and learn 3-point lighting.  First and foremost it will bring your subjects to life.  Second, even the most basic cameras and lenses can capture good video of a well-lit scene.