This disclosure provides systems, methods and apparatus for providing illumination by using a light guide to distribute light and for determining spacing between light turning features in the light guide. In one aspect, a light intensity profile along a first axis is determined and the pitch of light turning features along that first axis is varied based upon this profile, while the pitch along a second crossing axis (for example, an orthogonal axis) and the sizes of the light turning features remain unchanged. In some implementations, an apparatus includes a light guide having an array of light turning features configured to turn light from at least one light emitter. The light turning features can be non-uniformly spaced apart along a first axis such that pitches vary non-monotonically and, along a second axis that crosses the first axis, the light turning features are spaced apart with substantially the same progression.