Character-related factors
Type width
Type widths, defined as the interior distance between the two stems of the letter »n«, range from condensed to extended. A normal type width is approximately 50% of x-height.
The smaller counters and apertures found in condensed typefaces make reading more difficult. Extended typefaces take up more space horizontally, reducing the number of letters that can be recognised in one fixation during the reading process, and so create additional difficulties for people with a restricted field of vision. Standard type widths are therefore recommended.
Fixation
When reading quickly, our eyes move in small jumps, the saccades. It is only in the centre of vision, at the fixation point, that we see characters clearly. People with a restricted visual field, those learning to read and inexperienced readers will recognise fewer letters per fixation. The wider the letters are, the fewer characters can be recognised within a fixation.
We recognise ten to twelve letters per saccade – three or four to the left of our centre of vision and seven to nine to the right. The characters can only be seen clearly in the centre of vision, the fixation.
Summarized Recommendations
Type width
- Use standard type widths
- Avoid condensed and extended typefaces