Distance from Fixture to Task
Contrary to intuition, the distance of a fixture from the task has no effect on task lighting efficiency, if the light distribution pattern of the fixture can be shaped properly. Light is not absorbed in the space between the fixture and the task. However, fixtures with poor control of the light distribution pattern must be mounted close to the task to minimize light loss outside the task area.
The distance between the fixture and the task matters primarily because it affects the ratio of the fixture surface area to the distance from the task. (To review, we want this ratio to be large to prevent excessive shadowing and to reduce surface brightness.) For example, if the distance of a fixture from the task is doubled, the surface area of the fixture must be increased by a factor of four to maintain the same ratio. Larger fixtures are more expensive, more difficult to install, and more difficult to make attractive. So, try to keep task lighting fixtures reasonably close to the activities. The limitation on getting the fixture close to the task is maintaining sufficiently uniform illumination