EXPOSURE
When talking about exposure in photography, film and video, we often refer to the 'exposure triangle'
ISO – is the measure of the film/ camera sensor’s sensitivity to light
Aperture – is the size of the opening in the lens
Shutter Speed – is the amount of time that the shutter is open
Each of these effect how much the image is exposed, under or over. They also effects the image in other ways.
We can also use ND Filters to control exposure, these are built into many video camera's (inc. Canon C100 and Sony Z7), they can also be applied as a filter screwed onto the end of the lens
The video tutorial below gives a good overview of the three basics of Exposure in Photography
You can use various tools such as Wave Form Monitor in the camera to make sure your exposure is right, see this video below as an explanation on how it works.
Another tool that can be useful is Zebra. You can use Peaking to help with focus.
These guides and video tutorials for the C100 are useful.