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Dear Theresa In response to your first question, one way to do this is to look closely at the image (eg changing the contrast level) with the predicted pattern superimposed after indexing, or alternatively just integrate the image and look at the reported mean I/sigmaI as a function of resolution. Both of these are trivially easy to do with iMosflm. You need to remember that any number of issues (eg zingers, hot pixels, ice diffraction) can give rise to what are apparently significant intensity spots, so to distinguish between "real diffraction" and artifacts you need to look carefully at the spot size and shape as well as its intensity (and whether it is predicted). The other point to bear in mind is that generally there is no problem integrating the images to a resolution a bit beyond where spots are visible, eg to 3.0-3.2Å when spots are only visible to ~3.4-3.5Å and then using the merging or refinement statistics to decide the "true" resolution of the data. Best wishes, Andrew Leslie On 8 Oct 2012, at 23:36, Theresa Hsu wrote: > Dear all > > I took some images from test crystal and tried to index them to get > cell parameters, not enough for structure solution. I can see spots > at 3.5 A with ADXV but when I indexed, XDS reports up to 3.0 A in > INCLUDE_RESOLUTION_RANGE in XDS_ASCII.HKL. > > Questions: > > 1. How do I know that the spot at 3.0 is not background noise? > 2. What is the function of FRAME.cbf file? > > Thank you. > > Theresa