International
Tables for Crystallography Volume F Crystallography of biological macromolecules Edited by M. G. Rossmann and E. Arnold © International Union of Crystallography 2006 
International Tables for Crystallography (2006). Vol. F. ch. 18.5, p. 411
Section 18.5.7.1. Fullmatrix comparison with the diffractioncomponent precision index^{a}Chemistry Department, UMIST, Manchester M60 1QD, England 
The DPI (18.5.6.9) with R was offered as a quick and rough guide for the diffractiondataonly error for an atom with . The necessary data for the comparison with the two unrestrained fullmatrix inversions of Section 18.5.5 are given in Table 18.5.7.1. For concanavalin A with , the fullmatrix quadratic (18.5.4.2b) gives 0.033 Å for a carbon atom and the DPI gives 0.034 Å for an unspecified atom. For the immunoglobulin with , the fullmatrix quadratic (18.5.4.2a) gives for a carbon atom, while the DPI gives 0.22 Å.

For these two structures, the simple DPI formula compares surprisingly well with the unrestrained fullmatrix calculations at .
For the restrained fullmatrix calculations on concanavalin A, the quadratic (18.5.4.2c) with gives for a carbon atom, which is only 15% smaller than the unrestrained 0.033 Å. This small decrease matches the discussion of and in Section 18.5.4.1 following equation (18.5.4.1). But that discussion also indicates that for the immunoglobulin, the restrained , which was not computed, will be proportionaly much lower than the unrestrained value of , since the restraints are relatively more important in the immunoglobulin.