biostudies-literature00470Cowtan KBiotechnology and Biological Sciences Research Council470-8https://www.ebi.ac.uk/biostudies/studies/S-EPMC2852311biostudies-literatureUnknown66(Pt 4)Classical density-modification techniques (as opposed to statistical approaches) offer a computationally cheap method for improving phase estimates in order to provide a good electron-density map for model building. The rise of statistical methods has lead to a shift in focus away from the classical approaches; as a result, some recent developments have not made their way into classical density-modification software. This paper describes the application of some recent techniques, including most importantly the use of prior phase information in the likelihood estimation of phase errors within a classical density-modification framework. The resulting software gives significantly better results than comparable classical methods, while remaining nearly two orders of magnitude faster than statistical methods.Acta crystallographica. Section D, Biological crystallographyRecent developments in classical density modification.PMC2852311BB/D522403/1Cowtan K47falseRecent developments in classical density modification.Classical density-modification techniques (as opposed to statistical approaches) offer a computationally cheap method for improving phase estimates in order to provide a good electron-density map for model building. The rise of statistical methods has lead to a shift in focus away from the classical approaches; as a result, some recent developments have not made their way into classical density-modification software. This paper describes the application of some recent techniques, including most importantly the use of prior phase information in the likelihood estimation of phase errors within a classical density-modification framework. The resulting software gives significantly better results than comparable classical methods, while remaining nearly two orders of magnitude faster than statistical methods.2010-01-01T00:00:00Z2010 Apr2021-02-20T23:56:38Z2019-03-27T00:00:46ZS-EPMC28523112038300010.1107/S090744490903947X