Vario lens
Vario lenses allow the manual variation of their focal length. Colloquially, this is called "to zoom". But actually, vario lenses are not zoom lenses. If we vary their focal length, we also have to readjust their focus. The advantage of vario lenses: small, lightweight and low-priced.
The Imaging Source, a manufacturer of industrial cameras, recommends vario lenses, if the machine vision application requires a short focal length (wide angle).
Beyond their variable focal length, vario lenses are selected according to the rules that apply to "normal" C-mount lenses.
