Histograms have become an invaluable tool when assessing exposure. Combined with the ability to pick at a photo you just took, they have replaced the use of a light meter for many photographers. This is true for video as well as stills.
Photographer and videographer Cédric Hauteville started a new web series and his first episode deals with Histograms For Video. He covers the obvious like what a histogram is and how to use it, but also some more advanced topics like the importance of looking at a histogram along with the photo, and how to use histograms to judge the white balance settings.
My two big takeaways from the clip is that clipping is not always bad
and that Magic lantern can add a live video histogram (similar to external monitors) to a Canon camera.
[Histograms – Scopes under the lens | Cédric Hauteville]