sentences:  The main benefit of a video magnifier over purely optical magnification is that the video magnifier allows greater magnification across a larger field of view.With optical lenses, the field of meaningful, in-focus view is reduced with increased magnification.Thus, while a "full page magnifier" based on a fresnel lens can span some 625 cm2 (A4), it typically achieves no more than 1.4x magnification (advertised as "2x" if measured by area instead of the scale factor); an aspheric segment hand magnifier can achieve a scale factor in excess of 2 (area factor in excess of 4) but typically measures no more than 10 cm x 3 cm, and higher magnification factors require conventional lenses that focus on a very small area.