International
Tables for Crystallography Volume B Reciprocal space Edited by U. Shmueli © International Union of Crystallography 2010 
International Tables for Crystallography (2010). Vol. B, ch. 2.5, p. 305
Figure 2.5.2.3
J. M. Cowley^{a}


Figure 2.5.2.3
The functions , the phase factor for the transfer function of a lens given by equation (2.5.2.33), and for the Scherzer optimum defocus condition, relevant for weak phase objects, for which the minimum value of is . 