Work at this level shows little understanding of the basics of film-making. It may for example have unsteady photography or problems with exposure, obvious distortions of sound or unattractive abrupt changes. It may lack understanding of the conventions of editing. The film may typically lack effective story or structure and fail to engage the viewer.

Clearly each rating will inevitably cover a range of attainment levels, and will be subjective to some degree; film is a work of art not science.
Please also be aware that the general standard of films drifts over time.