Digital media

Though many of the factors dealt with in the preceding sections apply to all types of media, there are some important differences in the production of digital media, in particular for web applications. This section deals with some of these specific features and provides useful sources for further research.

The Web Content Accessibility Guidelines (WCAG) published by the World Wide Web Consortium (W3C) are the international standard for the implementation of accessible online media and digital applications. The latest published version is WCAG 2.1. In Germany, the implementation of all public web-based applications by the Federal German authorities is governed by the Accessible Information Technology Regulations (Barrierefreie-Informationstechnik-Verordnung, BITV 2.0), which are explicitly based on WCAG. Both require that information be presentable to users in a way that is perceivable, operable, understandable and robust and take auditory, physical, speech, cognitive, language, learning and neurological as well as visual disabilities into account.

Whereas the recommendations provided on leserlich.info are primarily conceived with communication design in mind and as such concentrate on ensuring that information is perceptible, a large part of WCAG deals with technical programming requirements. This includes the core requirement that digital information be provided in a standardised form so that it can be used by as many programs and devices as possible. In contrast to printed materials, which have a fixed, physical form, the aim is to be able to adapt the form of digital information as freely as possible to the needs of the individual user. However, there are certain external factors that can hinder the individual adaptation of digital information. These include the speed of technical developments, the use of old and outdated hardware and software and a lack of technical knowhow on the part of the user. In order to meet the requirements of inclusive communication design despite these constraints, we must go beyond the requirements of WCAG and optimise the readability of digital media to the point where they are accessible to as many people as possible in their original state, i.e., before any subsequent individual adaptation takes place.

With this in mind, we have identified two key issues not dealt with in sufficient depth in the current version of WCAG.

Font size

The nature of digital media means that they display typefaces in pixels. As a result, font size is also specified in pixels. This means that the optical/metric font size is dictated by the size of pixel used, which may vary by up to 300% depending on screen resolution and device configuration. Where the same design is to be used on different devices, each with an unknown resolution, there is no choice but to use average values for the most common screen resolutions (pixel sizes).

This is currently a virtual resolution of 100 ppi (pixels per inch) for desktop and notebook screens, 150 ppi for tablets and 155 ppi for smartphones. The metric size of a pixel in millimetres is calculated by dividing the virtual resolution in ppi by 25.4.

Virtual resolution

The actual resolution of a screen is expressed as the number of real pixels per inch. However, devices only rarely use actual resolution to calculate the size of image elements to be displayed. In modern devices, for example, technologies such as retina and high-DPI displays combine a number of real pixels to form one virtual pixel. As a result, the term virtual resolution refers to the resolution used by device software to calculate display size. In general, you will not know the virtual resolution of a given device and so will have to calculate it mathematically. The device-specific average values given above were determined using the https://mydevice.io/devices/ device database. The devices with the greatest deviation were excluded from the calculation.

Responsive design

To ensure that digital applications such as websites, for example, can be displayed equally well on a range of devices, they must be able to adapt to various screen sizes and formats. Apps should be constructed to ensure that all elements are visible without being enlarged, reduced or moved horizontally. A vertical layout in which all sections can be reached simply by scrolling down is ideal.