Statement issued on ‘metrics for crystallographic diffraction- and fit-data: a review of existing ones and the need for new ones’ from Julian Henn

In his preceding review ‘Metrics for crystallographic diffractionand fit-data: a review of existing ones and the need for new ones’ Julian Henn (JH) calls for the need to address problems with σ (Io)s. To corroborate this need he refers in chapter 6 mainly back to two of our examples published recently. He presents them not as the intended bench-mark investigation to avoid overfitting in charge density models but as failed case studies [ref 18 in JH’s review]. Clearly we agree with JH that there are problems with σ (Io)s. As much as we appreciate his overarching aim to improve X-ray structure analyses, we nevertheless feel the need to respond to some of the accuses.