Screen magnifier
Encyclopedia
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 shortcut 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 controller 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.
Screen magnifiers commonly provide several other features for people with particular sight difficulties:
Assistive technology
Assistive technology or adaptive technology is an umbrella term that includes assistive, adaptive, and rehabilitative devices for people with disabilities and also includes the process used in selecting, locating, and using them...
suitable for visually impaired
Visual impairment
Visual impairment is vision loss to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive...
people with some functional vision; visually impaired people with little or no functional vision usually use a screen reader
Screen reader
A screen reader is a software application that attempts to identify and interpret what is being displayed on the screen . This interpretation is then re-presented to the user with text-to-speech, sound icons, or a Braille output device...
.
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 shortcut 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 controller 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.
Features
Ranges of 1- to 16-times magnification are common. The greater the magnification the smaller the proportion of the original screen content that can be viewed, so users will tend to use the lowest magnification they can manage.Screen magnifiers commonly provide several other features for people with particular sight difficulties:
- Color Inversion. Many people with visual impairments prefer to invert the colors, typically turning text from black-on-white to white-on-black. This can reduce screen glare and is useful for elderly people suffering from age-related macular degenerationMacular degenerationAge-related macular degeneration is a medical condition which usually affects older adults and results in a loss of vision in the center of the visual field because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness and visual impairment in older adults...
. - Smoothing Text can become blocky and harder to recognise when enlarged. Some screen magnifiers anti-alias or smooth text to compensate.
- Cursor customisation. The mouse and text cursors can often be modified in several ways, such as circling it to help the user locate it on the screen.
- Different Magnification Modes Screen magnifiers can alter how they present the enlarged portion: covering the full screen, providing a lens that is moved around the un-magnified screen, or using a fixed magnified portion.
- Screen reader. Some magnifiers come packaged with a basic screen readerScreen readerA screen reader is a software application that attempts to identify and interpret what is being displayed on the screen . This interpretation is then re-presented to the user with text-to-speech, sound icons, or a Braille output device...
, allowing whatever the user is pointing at to be read out.
Screen magnifiers bundled with the OS
- A Magnifier application has been included within the Microsoft WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
operating system since Windows 98Windows 98Windows 98 is a graphical operating system by Microsoft. It is the second major release in the Windows 9x line of operating systems. It was released to manufacturing on 15 May 1998 and to retail on 25 June 1998. Windows 98 is the successor to Windows 95. Like its predecessor, it is a hybrid...
. - On Mac OS XMac OS XMac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
, the built-in screen magnification feature can be used at any time holding the Control key and scrolling the mouse wheel to zoom in or zoom out. - Many LinuxLinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
Operating systems utilize a program called Compiz-Fusion which has a highly configurable plugin named "Enhanced Zoom Desktop" - HaikuHaiku (operating system)Haiku is a free and open source operating system compatible with BeOS. Its development began in 2001, and the operating system became self-hosting in 2008, with the first alpha release in September 2009, the second in May 2010 and the third in June 2011....
includes an application called Magnify
Screen magnifier products
- Dolphin LunarDolphin Computer AccessDolphin Computer Access is a British company that designs, creates and sells software for people who are blind or have vision and print impairments, Dyslexia and other specific learning difficulties. The company was set up in 1986 and now has offices in the UK, US and Sweden...
- Magnifier (Windows)Magnifier (Windows)Magnifier is a screen magnifier program for the visually impaired to use Microsoft Windows. When it is run, it creates a bar at the top of the screen that greatly magnifies where the mouse is. Magnifier was first included as a sample in the Active Accessibility SDK/RDK for Windows 95 and later made...
- Virtual Magnifying GlassVirtual Magnifying GlassVirtual Magnifying Glass is an open source, screen magnification tool for Microsoft Windows and Linux.Virtual Magnifying Glass is designed for the visually impaired and others who need to magnify part of the screen...
- Cross platform magnifier application - ZoomTextZoomTextZoomText is a screen magnifier for Microsoft Windows, developed by Ai Squared. The first version was released for DOS in 1988, and the first version for Windows was released in 1991...