Tables for
Volume B
Reciprocal space
Edited by U. Shmueli

International Tables for Crystallography (2010). Vol. B, ch. 2.5, p. 380


P. A. Penczekg

The geometrical constraints of the 2D alignment problem. (a) The reference 2D particle is placed within a square image frame n × n pixels and its size is such that it can be bounded by a circle with a radius r no larger than 0.9n. (b) The particle projection, the size of which is bounded by the same radius as the reference view, can be located within a circle centred on discrete locations within the image frame, such that the maximum translation is k = (n/2) − r. The number of possible translations is (2k + 1)2. Reprinted from Joyeux & Penczek (2002)[link] with permission from Elsevier.