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usability of type size increments

feature article d0A26 edition d1S26





for many designers today, measures of typographic size no longer depend on the measurement of mechanical type. indeed, elements of design are often developed with reference to perceptual or to proportional rather than fixed scales of measure. as design workflows have been transformed by developments of computerized typography, there are probably many design scenarios and practices that do not call for units of type to be configured in terms of pre-metric measures.

for improved usability of the selection of type size units in a software application, options for measures of type size may call for an approach that does not depend on any one particular scale of length. different users might work with different units for typography, units that might include the use of millimeter, or might include one of several other customary measures of type size such as the Postscript point.

for further reading on metric characteristics of typography, readers can refer to Metric typographic units by Marcus Kuhn (2003).

although I have recently studied the preparation of documents in terms of millimeter measures, as of this writing there remain certain gaps in software support for measures of type in terms of metric, and thus more practicably comparable, units of length.


type as dimensionless

a unit of type size that does not depend on a particular scale of length can be said to be dimensionless. one example of a dimensionless unit is the pixel, or 'picture element'. the dimensionless unit of pixel is widely used in many areas of computing and multimedia production. the size of a pixel is only set with reference to a particular resolution: for example 240 pixel per centimeter, or 72 pixel per inch.

in this article I will suggest that a dimensionless unit of type size can improve the usability of working with units of type size, especially in the context of a large number of possible metric and traditional units for type size.


usability review of app typography

toward this I will analyze typography features of some software applications for Adobe Creative Suite version 4, for which some support is provided for different units of type size. the analysis will proceed in terms of a tentative dimensionless unit of 'type increment size'. herein I will refer to such a unit as a 'typ' (compare pronunciations of first syllable of 'typical' with pronunciation of word 'tip').

the objectives of this article are to describe some principles of workspace and interface design that can accommodate improved usability of typography features. an earlier edition of this article was first published prior to my use of the version 5 software applications. this article will not compare differences in version 5 from version 4 of the software applications. as version 5.5 of the Creative Suite is very recently now available from Adobe, it bears mention that this edition of the article does not compare differences in the usability of typography features from versions 4, 5, and 5.5.


units as singular

a first matter, although minor from a user viewpoint, can serve to enhance the presentation of technical information about units.

if a particular use of unit information is tabular or technical in nature, then writers of technical information should consider writing units in singular rather than plural form. this is required for symbolic representations of a unit, such as mm for millimeter, yet can also be quite useful for long form representations of technical information. rather than writing 'millimeters' for an expression of a technical unit, simply write 'millimeter'. rather than writing 240 pixels per centimeter, write 240 pixel per centimeter. the plural form doesn't add any important information. in those cases where some units in a table might be expressed as plural while others might be expressed as singular, then the effort to write the plural may very well encompass too much information for the task.

thus in Adobe InDesign 6.04 > Preferences > Units & Increments, the 'Ruler Units' section would be revised to 'Ruler Unit'. and the items in the 'Horizontal' and 'Vertical' drop-menus would be listed more practicably as singular rather than as plural forms. for example, millimeter (mm), rather than Millimeters.


framework of type size increment

a next and more important matter concerns the presentation of type size in terms of a dimensionless unit. the section 'Point/Pica Size' would thus be renamed something like 'Type Increment Size', and could include an option to set a default type size in terms of a metric scale like the millimeter (mm).

continuing the analysis, the label 'Points/Inch:' would be renamed in terms of some term that can be used for the concept of 'type size increment'. depending on what type increment size is selected by a user, the 'typ' could be configured in terms of some multiple or submultiple of the millimeter, or it could be set to a Postscript point, or some other unit.

such a framework could make possible the selection of a type size increment by a user in terms of any of the following options:


table 01: options for type size

typ per millimeter
04 typ per mm (0.25 mm)
10 typ per mm (0.1 mm)
20 typ per mm (0.05 mm)
Postscript point (72 typ/inch)some 2.835 typ per mm
Traditional point (72.27 typ/inch)some 2.845 typ per mm
Custom(user prompt for number of typ per mm)

these options would have no effect on the definition or use of a pica when a Postscript or a Traditional point size is selected. especially if the pica is organized in terms of a gridline per designated number of typ, then a user would have an option to configure the use of a practical grid consisting of typ multiples. such a grid could consist of a pica grid of points (a Pica gridline every 12th Postscript point), yet could also consist of a metric millimeter grid of designated millimeter submultiples (a millimeter gridline with same number of subdivisions as typ per mm).

wherever a typ would be displayed in the interface, it might be simpler and clearer to display the value without a dimension. however it would also be useful for a user to have a means to view more information about type size. this information could be held in a panel or window for information about type size increments. perhaps such a feature would provide a means for a user to view a length dimension of a type size increment value on the visible portion of a collapsed panel, in addition to a means of viewing a calculation in terms of another type size increment value.

in this way the main workspace can display type size values as a number without having to repeat the information about what unit it is in every type size field, or without needing to be able to calculate any unit other than a typ.

a similar approach could also very well improve the selection of type size units in Adobe Photoshop 11.0.1 > Preferences > Units & Rulers: the section 'Point/Pica Size' could also be revised in terms of options for 'Type Increment Size'.


other comments

the above reflects features of typography that I think would be great to use with software applications. given the development of recent capabilities for the design of software interfaces, i would think that the development of features of typographic size as they are envisioned above would be feasible.

improved support for type size incrementation would enable designers to plan both the layout and the typography of documents in terms of a common practicable unit, that of the millimeter. one possible benefit is that designers might be able to estimate copyfits of type for a layout with less additional calculation. one definite benefit would be that designers could more readily prepare layouts exclusively in terms of the millimeter, a metric unit of measure.


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