Measuring type size and line space

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4. Considerations


There are at least six considerations that question the value of the measurements of x-heights of information on packaging and in package leaflets.


A. Understanding and reading

Although it is possible to determine the dimensions of printed texts accurately, it has little to do with ‘clear and comprehensible’ or ‘enabling people to act appropriately’. Texts can be smaller and still be easily legible, and they can be larger and be very hard to read. There is no relation between ‘understanding’ and ‘type size’, nor between ‘minimal type size’ and ‘easy to read’.


The only way to find out if a text can really be used (find information, read information, understand information, consider information, apply information) is to ask people to read it. Observing people while they read and asking questions afterwards to see how information is interpreted are essential. Asking people to apply the information in a particular situation gives some insights if a text could be effective.


B. Dimensions in the Readability guideline.

It is surprising that there is a difference between the typesize of texts in a package leaflet and the typesize of texts on labelling. The difference between ‘as measured in Times new roman 9 pt’ and ‘an x-height of 1.4 mm’ turns out to be 0,022 mm. This is too small to notice with an unaided eye. A motivation for this difference in the Readability guideline is missing.


Furthermore, there is hardly any research that indicates that 1,4 mm would be a suitable minimal dimension. Only two articles have been published that indicate this. [Please contact me if there are more.] These articles are:

  1. Legge GE, Bigelow CA. 2011. Does Print Size Matter for Reading? A Review of Findings from Vision Science and Typography. Journal of vision 2011; 11(5). doi:10.1167/11.5.8.

  2. Waarde, K. van der 1999. Typographic dimensions and conventional wisdom: a discrepancy? Technical Communication. First Quarter. February. pp 67-74


C. Body sizes in points and x-height in millimetres

There is no straightforward relation between point sizes and millimetres. It is not possible to convert one into the other. This has a historical reason. ‘Body’ and ‘leading’ indicate the vertical dimension of a pieces of metal. In metal type, there is always a bit of space above and below each character on the body. The dimensions of this space are determined by the type designer and can vary. Furthermore, the dimensions of the x-height on a body can vary too. That is why some typefaces have a larger or smaller x-height on the same bodysize.


After a text has been printed, it is not possible to determine these dimensions of the body or the leading anymore. However, it is possible to measure the dimensions of printed characters: x-height and linespace.



















D. Calculating the x-height for Times New Roman.

Digital type is designed on a coordinate grid of 1000 by 1000 units per em (upm) in Postscript and OpenType, or 2048 by 2048 upm in Truetype. Software uses the coordinates of this grid to calculate the dimensions of type for printers and on screens. These standards make it possible to calculate the x-height.


The x-height of Times New Roman is 0.448. That means that the height of the lower case x is 44,8%. One typographical point is 0.35278 mm. The height of nine points is 3.175 mm. The x-height of nine points TImes New Roman is therefor 44.8% of 3.175 mm: 1,422 mm.


E. There is not ‘one’ Times new roman: there are several variations.

There are different companies (foundries) who sell ‘Times New Roman’. The original is by Monotype, but there are specific versions by companies such as Microsoft and Adobe/Linotype. Although these typefaces might look very similar, there are small differences.


F. There is not ‘one’ point size: there are several variations.

There are several different types of ‘points’ (Andrew Boag, Typographic measurement: a chronology, Typography papers, I, Reading, 1996, p. 105-122.).


There is the traditional European Didot-point, which is approximately 0.38 mm. The traditional Anglo-American point is slightly smaller. In that system type and lines are measured in points and picas. One pica-point is equal to 0.35146 mm. Both these traditional points have largely been replaced by the PostScript point. The digital PostScript point is 1/72 inch (approximately 0.35278 mm.).

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