International
Tables for
Crystallography
Volume B
Reciprocal space
Edited by U. Shmueli

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

Figure 2.5.7.2 

P. A. Penczekg
[Figure 2.5.7.2]
Figure 2.5.7.2

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.