A membrane assembly for use with a three-dimensional imager to obtain a topographical plantar image of a foot is provided. The assembly includes a support structure having a front end and a rear end elevated relative to the front end, and a flexible membrane suspended from the support structure and configured to receive and support an entire plantar surface of the foot. The membrane defines and encloses an upper portion of an inflatable chamber, and includes a forefoot- and a rearfoot-receiving region respectively adjacent to the front and the rear end of the support structure. The rearfoot-receiving region is under less tension than the forefoot-receiving region. The imager is positionable under the membrane in order to acquire the plantar image when the foot is disposed on the membrane. An apparatus including a membrane assembly and a three-dimensional imager, and a method for imaging a foot are also provided.