When selecting the cameras for a video production project, the ability to use different lenses can be vital. As an example, if you were to use B roll lenses, they are fixed lenses, so wouldn’t be able to use a 22x, or a wide angle lens.
Because lens selection is so important, people have gone to the large sensor interchangeable lenses of cameras such the Sony FS7M II or FX9, or the FX6 because it gives them flexibility in the field.
Modern cameras shoot 4K because it gives the editors more flexibility in post production, i.e. resizing, framing, or zooming in for a closeup.
Smaller cameras are used for quick shoots, where quick maneuvering is necessary, i.e. in crowded situations, B roll at a conference, or demonstrations. Its important to note that smaller cameras such as the Panasonic AGDVX200 and the Sony Z 280 can work for webcasting live events.
More information: Cameras