Apply the legibility principles to screen reading

Question

How to apply the legibility principles to screen reading? What is important point for it?

What is the difference between the "legibility" and "readability"?

Answer 1

If you look at the dictionary definitions, it doesn't seem like a lot of distinction between the two:

• Legibility - Also called visibility. Typography. the quality of type that affects the perceptibility of a word, line, or paragraph of printed matter.
• Readability - Typography . the property of type that affects the ease with which printed matter can be read for a sustained period.

Practically speaking, legibility has to do with being able to recognize the characters on the screen. Readability has to do with the long term effects of using the font/background/etc. Assuming the font is legible (you can make sense of the letters), a reader may experience eye fatigue reading the font for an extended period of time.

You don't want to base the main content of a web site with a font that has low readability. However, using a splash of fonts with lower readability for your titles can give your design freshness. You just don't want to overdo it.

Consider these example problems:

• The font is too small - even with anti-aliasing when a font gets too small you are no longer able to distinguish between some of the characters. This is a legibility problem.
• Horizontal gradient background - The reader's eyes have to adjust to the difference in contrast between background and text. When the reader starts the next line, they have to sharply readjust their eyes to the new contrast. With prolonged reading this causes eye fatigue and headaches. It is a readability problem.