A Two-Week In-the-Wild Study of Screen Filters and Camera Sliders for Smartphone Privacy in Public Spaces

TL;DR

This study investigates tangible smartphone privacy tools in public using a two-week in-the-wild, mixed-method design (N=22). It evaluates a privacy screen filter and a camera slider within the Contextual Integrity framework to understand effects on privacy perception, behavioral adaptation, usability, and social dynamics. Quantitative results show the screen filter reduces discomfort and unwanted screen exposure, enabling broader use of sensitive apps, while qualitative analysis highlights social and usability barriers for the camera slider. The work informs design implications for context-aware, hybrid tangible privacy solutions that balance usability, perceived privacy, and social norms in public smartphone use.

Abstract

Smartphone usage in public spaces can raise privacy concerns, in terms of shoulder surfing and unintended camera capture. In real-world public space settings, we investigated the impact of tangible privacy-enhancing tools (here: screen filter and camera slider) on smartphone users' reported privacy perception, behavioral adaptations, usability and social dynamics. We conducted a mixed-method, in-the-wild study ($N = 22$) using off-the-shelf smartphone privacy tools. We investigated subjective behavioral transition by combining questionnaires with semi-structured interviews. Participants used the screen filter and the camera slider for two weeks; they reported changes in attitude and behavior after using a screen filter including screen visibility and comfort when using phones publicly. They explained decreased privacy-protective behaviors, such as actively covering their screens, suggesting a shift in perceived risk. Qualitative findings about the camera slider suggested underlying psychological mechanisms, including privacy awareness and concerns about social perception, while also offering insights regarding the tools' effectiveness.

Figures (5)

• Figure 1: Everyday privacy challenges smartphone users face in public spaces, from physical intrusions like shoulder surfing (left) to invisible risks like unauthorized camera access and online data sharing (right). In addressing such challenges, we studied two tangible privacy tools; privacy screen filter (left) and camera slider (right).
• Figure 2: The three phases for our study; pre-intervention, intervention, and post-intervention.
• Figure 3: Tangible privacy tools provided to the participants of our study.
• Figure 4: Privacy Perception - Behavioral Adaptation *: $p < 0.05$, **: $p < 0.01$. Original questionnaires were 10-Likert scale and we cut above 7 point of graph for readability.
• Figure 5: Percentage differences per app avoidance usage reported in pre (blue) and post (red) interventions.