LED lighting in a linear form factor can provide valuable accent lighting and vertical illumination in architectural cove and graze applications. Ideally, linear lights provide a smooth gradient of light onto a surface without disturbances along their length. However, socket shadows between discrete fixtures and multiple LEDs per fixture can lead to visible nonuniformities, often worse near the light source but mixed to uniformity further away. Perceived mixing distances in the illumination patterns of a variety of linear light sources were assessed visually, and objective metrics based on illumination measurements were developed. Accurate predictions of mixing distances are shown based on trends in CIE DE2000 color errors computed between the measured light pattern and analogous Gaussian-weighted local neighborhood regions. Effects of variations in parameters of DE threshold and neighborhood size and shape are discussed.