Hi I'd agree with Kay here - since the edge of the detector is at ~2.8Å. It is almost always worthwhile integrating to a higher resolution than you can see spots on the images - for what I would call "normal" datasets, I would always integrate to ~0.2Å higher (as a first estimate), then after examining scaling statistics (e.g. correlation coefficients!) decide if you can actually integrate even higher. For "modern" extra fine phi slicing, it's usually worthwhile integrating to an even higher resolution before making any decisions about the "true" resolution, especially if you have non-negligible background on the images.
There are a couple of issues with integrating to *much* higher resolution than you actually have - one is due to the crystal & detector refinements becoming less stable if you include too many reflections with insignificant !/sig(I) - i.e. "refining against noise", and the other is in optimising the profiles & measurement boxes (again, using "noise" to determine these will not lead to optimal values). BTW, unless you have a *really* good reason for scaling with SCALA, I would seriously consider updating your CCP4 installation and using Aimless instead. Phil Evans is no longer developing SCALA, and doesn't seem to have updated the SCALA release notes since 2010, so I suspect that any newer versions (most recent is 3.3.21) only contain minor bug fixes (but I could be wrong). On 23 Jul 2013, at 08:11, Kay Diederichs wrote: > Hi Stefan, > > you write > "The diffraction pattern looks great, the 3.4A reflections are visible by eye > and the edge of the detector is about 2.8A." > and for the 3.4A data Mean((I)/sd(I)) in the highest shell is 2.3 . > > I'm tempted to ask: what prevents you from using higher resolution data to, > say, 3.2 or 3.0 A - what do you gain by throwing reflections away? Using > higher resolution _will_ reduce overfitting, and should improve the model. > > In the presence of NCS, Rfree will be biased towards Rwork. In your case of > high-order NCS, you might consider choosing the free reflections in thin > shells in reciprocal space. > > HTH, > > Kay >> >> >> The diffraction pattern looks great, the 3.4A reflections are visible by eye >> and the edge of the detector is about 2.8A. The crystals were 10x20x50 um in >> size and spacegroup is P6522. >> >> Harry -- ** note change of address ** Dr Harry Powell, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH Chairman of European Crystallographic Association SIG9 (Crystallographic Computing)
