Expanding the Expressive Potential of Tactile Photography for People with Visual Impairments through a Depth- and Luminance-Based 2.5D Relief

Abstract

Photographs are powerful tools for storytelling, preserving memories, and self-expression. However, people with visual impairments (PVI) face significant challenges in accessing photographic content. Recently, generative AI tools such as Be My AI have made it easier to obtain verbal image descriptions, yet language alone cannot fully convey the rich visual information that photographs contain. Tactile representation offers an alternative means of access, but traditional tactile graphics?typically based on 2D contours?are limited in expressiveness. To address this limitation, we propose a novel method for generating 2.5D reliefs from photographs by integrating depth estimation and luminance information. This approach allows continuous representation of depth while reproducing luminance-based features such as text and patterns as tactile variations, thereby achieving richer tactile expression. We conducted a user study with 12 participants with visual impairments (six who are blind and six with low vision), comparing three types of tactile models: ?2D tactile photographs, ?depth-based 2.5D reliefs, and ?depth?luminance-based 2.5D reliefs. To analyze user preferences, we applied the Analytic Hierarchy Process (AHP) based on five evaluation criteria. The results demonstrated the effectiveness of integrating depth and luminance information, and further provided insights into how users' motivation and prior experience influence their tactile exploration and understanding of photographs.

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