Screen Magnifier

A screen magnifier is software that interfaces with a computer's graphical output to present enlarged screen content. It is a type of assistive technology suitable for visually impaired people with some functional vision; visually impaired people with little or no functional vision usually use a screen reader.

The simplest form of magnification presents an enlarged portion of the original screen content, the focus, so that it covers some or all of the full screen. This enlarged portion should include the content of interest to the user and the pointer or cursor, also suitably enlarged. As the user moves the pointer or cursor the screen magnifier should track with it and show the new enlarged portion. If this tracking is jerky or flickers it is likely to disturb the user. Also, the pointer or cursor may not be the content of interest: for example, if the user presses a keyboard shortcuts that opens a menu, the magnified portion should jump to that menu. Pop-up windows and changes in system status can also trigger this rapid shifting.

Screen magnifier can be especially helpful for people suffering from low vision, for example, many elderly users. However, Hanson points out that people with low vision often also suffer from additional disabilities such as tremors. Pramudianto et al. compared different magnification techniques to use a Wii Remote as a magnifier for distant displays. They determined that users have a lower error rate for selecting small targets if using one of the tested magnification techniques.