A foot for optical or photographic supports includes a telescopic rod having several telescopic members and, for each pair of adjacent telescopic members, an expanding stop mechanism mounted on one telescopic member of the pair and acting on the other telescopic member of the pair in order to block their relative sliding motion. The stop mechanism includes a radially expandable ring and an expander body for the ring for pressing the elements of the ring radially against an inner shell of the other telescopic member. The ring includes a plurality of barrel rollers having an outer shell with a curvature coinciding substantially with the curvature of the inner shell of the other telescopic member.