## 4 Results
### User Study  
Usability tests are a common method to gain subjective opinions and insights into what users think about a specific application. How much users actually benefit from applications and interfaces depends on the usability, suitability, and efficiency of technological solutions. Assessment and feedback by user groups is used to adapt applications and interfaces. User studies help to (a) collect information needs and requests of the user groups, (b) filter out the challenges that user groups have when using the tool, (c) identify usability weaknesses and (d) adapt the application to the user's needs. Different formats like workshops, surveys, and demo sessions were used to assess the 4D browser application depending on the available time and audience. The idea of the 4D browser is directly connected to research questions from art and architectural history. Scholars in these fields use images as the main source for analysis and argumentation and therefore turn to (online) digital image repositories. Common requirements of the users of digital heritage collections include ease of understanding the data and tools for accurate search and analysis, as well as an intuitive navigation and interfaces. Previous research has showed that 3D navigation can trouble users who are not used to 3D environments [322]. To evaluate the application, users were involved from the beginning of the development of the 4D browser. A workshop held at the Digital Humanities in the German-speaking Area (DHd 2018) conference in February 2018 involved 25 potential users, who were asked to reflect on their own experiences when using image repositories. Among a variety of mentioned issues and requirements were a dissatisfaction with insufficient filter options for existing platforms, requests for a faceted search functionality, to be able to label buildings within the 3D model, and for a feature to compare images. Since the topics and tools of the 4D browser application are very specific, it needed to be tested with relevant user scenarios and use cases. Potential users to consider and explicit tasks to solve are particularly useful when a prototype must be tested for initial reactions to the functions and interface. The real user group must be brought in later to ensure that their quality criteria have been met. The initial study was part of a workshop and contained different realistic tasks connected to the 4D browser [323]. The tasks help users to focus on and assess certain functions. They contain scenarios and problems that correspond to the knowledge and skills of an assigned persona that is part of the actual user group of the application. It is very important to properly have heterogeneous groups of test study participants. The persona approach seemed suitable for this as it helps participants from other academic fields who may not be able to fully envision the genuine intentions of the functions on the spot. Furthermore, thinking aloud was chosen to learn more about user needs and interactions. Instructions on how to approach the assignments as well as consecutive steps helped to guide the participants through the tasks. However, the instructions did not always name the specific tools and functionalities the participants should use. This allowed participants to observe whether they were named and placed in an intuitive manner. The data for the study were collected during a workshop offered by the research group at the DHd 2019 conference in Mainz, Germany. The topic of the workshop was usability testing for software tools in the digital humanities using the example of image repositories. Audio recordings of the participants were transcribed and coded using thematic analysis. This helped to evaluate how well the usability testing and the framework itself worked, revealing how participants dealt with personas and thinking aloud. The International Committee of Architectural Photogrammetry (CIPA) Conference in 2019 and 2023 also offered opportunities to gather feedback during demo sessions.