Video magnifier

Video magnifiers are electronic devices that use a camera and a display screen to perform digital magnification of printed materials.

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 (96.9 sq in) (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 two (area factor in excess of four) but typically measures no more than 10 cm × 3 cm (3.9 in × 1.2 in), and higher magnification factors require conventional lenses that focus on a very small area.

Very large video magnifiers are not typically portable, but they can still be used in home installations, libraries and classrooms.

Due to the high cost of dedicated-hardware video magnifiers, there has been some interest in software video magnification running on smartphones such as iPhone[1] and Android,[2] tablets such as iPad,[3] and laptops with suitably-mounted camera peripherals.