Let your reader know where to start reading, and where to continue reading. Headings, subheadings, initial capitals, and even numbered paragraphs, can act as important signposts through the text. Visual cues must be consistent throughout your document.
Long, grey "slabs" of type are like a long, boring speech -- people tend to tune out. Break up your document with short headings. These help the reader to easily find the section they want. You can also break up your document with small graphics, as long as it doesn't look messy.
White space is an important aid to legibility. Use wide margins and plenty of room at the top and bottom of your page.
Typefaces with a serif (small strokes at the end of characters) are generally easier to read than sans-serif typefaces:
However, some popular sans-serif typefaces have been carefully designed for maximum legibility:
A typeface's "x-height" is another important factor in readability. The x-height is the height of letters such as x, a and e, which have no ascenders (like h) or descenders (like y), compared with capital letters or letters with ascenders. Typefaces with a larger x-height are easier to read than typefaces with a smaller x-height.
Choose clear typefaces for your main text. Quirky or unusual typefaces can add character to covers and headings, but when used for text they will make your document much harder to read.
Avoid overusing bold or italics.
And never set a whole sentence or paragraph in CAPITAL LETTERS.
Black type on a white background is always the easiest to read. Type on a shaded background has an important role in forms design, and headings or highlighted quotes can be effective on a coloured background. But black on white is by far the best option for your main text.
For interest or design reasons, you may want to use dark coloured type on white, or black type on a pale coloured background or coloured paper -- but every step away from black on white will decrease legibility.
The least legible colour scheme is white or coloured type on a black background.
Four interrelated factors affect the legibility of body text:
- the line length
- the type size
- the space (or "leading") between lines of type
- the alignment of the right-hand side.
There's a limit to the number of words that readers can comfortably follow in a line of type. If the lines are too long, readers tend to lose track. But if the lines are too short, the reading flow is interrupted too often.
Generous space between lines increases legibility. The extra white space helps readers stay on the line. If the lines of type are too close, readers may accidentally read the same line twice, or skip a line.
There's an intimate relationship between line length, type size and space between lines. If you increase the length, you should also increase both the type size and the leading.
Setting text "flush left, ragged right" (so that the left-hand side of the page or column of type is straight, while the right-hand side is uneven) increases legibility. This is because the space between words stays even, and the eye "knows" immediately when it has come to the end of a line.
Conversely, "justifying" the type (where both sides of the column or page of type are straight) creates uneven gaps between words and sentences. These gaps interrupt the reading flow.
5 February 2004