Fidelity

An expression of how accurately a representation reproduces its source. A photograph is a high-fidelity visual representation of a scene but loses depth, sound, and smell. In accessibility and content adaptation, fidelity is a critical concern: when content is transformed from one design space to another — for example, a complex data visualisation converted to a text description — the fidelity of the adaptation determines how much information is preserved or lost. Alt text for an image is a low-fidelity representation that captures meaning but not visual detail. A long description may increase fidelity. The concept helps frame accessibility decisions as trade-offs: what level of fidelity is achievable and acceptable when adapting content for a different modality or capability?