Data Projectors - Zoom Ratio and Lens Focal Length

Zoom ratio is a measure of the difference between a lenses widest angle of projection, and its narrowest "telephoto" setting. A high zoom ratio is necessary to allow flexibility of positioning. Unfortunately most mid-price projectors have the same zoom ratio - somewhere in the region of 1:1.3 - this does not allow great scope in finding a suitable location where the projector will fill the screen. Focal length determines the "throw ratio" of a projector, i.e. the ratio of projected image size to projection distance. Again, there is little variation unless specialist projectors with interchangeable lenses are considered.

> Contrast Ratio