We present a study focusing on the usability of a wayfinding and localization system for persons with visual impairment. This system uses special color markers, placed at key locations in the environment, that can be detected by a regular camera phone. Three blind participants tested the system in various indoor locations and under different system settings. Quantitative performance results are reported. Categories and Subject Descriptors I.5.4 [Pattern Recognition]: Applications: Computer Vision. General Terms Algorithms, Performance, Experimentation, Human Factors. Keywords Wayfinding, Mobility, Orientation, Guidance, Recognition.