Assertion: overhead projector | /r/HasProperty | manual focusing mechanism
Facets:
value: normally
type: DEGREE
Source sentences:
text: Overhead projectors normally include a manual focusing mechanism which raises and lowers the position of the focusing lens (including the folding mirror) in order to adjust the object distance (optical distance between the slide and the lens) to focus at the chosen image distance (distance to the projection screen) given the fixed focal length of the focusing lens.