A screen magnifier is software that enlarges the image on the computer screen. It is useful for students with vision impairment with some functional vision; students with little or no vision usually use a screen reader.
The screen magnifier enlarges the cursor, and a focal point of the original screen content so that it covers the entire screen. The enlarged section is the main point of interest to the user, and as the user moves the cursor, the screen magnifier tracks it to show the new enlarged portion. Sometimes this is jerky and flickers, and this can be uncomfortable for the user, and pop-up windows and changes in system status can also cause problems.
Magnifiers range from 2x to 32x magnification – the greater the magnification, the smaller the proportion of the original screen content viewed at a time. Some products include screen readers that "read" the text on screen using synthesised voice.
Screen magnifiers often provide other features for people with vision impairment:
- colour inversion - screen glare can be reduced by inverting text from black-on-white to white-on-black
- “smoothing” text compensates for the blocky, hard-to-read effect of some enlarged text
- modification of mouse and text cursor (such as circling it to help the user locate it on the screen)
- different magnification modes to alter how the enlarged portion is presented according to the user’s needs.
Possible difficulties include:
- stylised fonts that are difficult to read
- inadequate contrast, especially if text is over graphics
- important information that is missed because it is over to the far right or down below the screen image
- small text or images that require increased magnification
- mouse-dependent commands (while some people do use the mouse, others find that combined with magnification, using a mouse creates too much movement around the screen).