A couple of extra comments on top of Bob's rather comprehensive recommendations, based purely on actually looking at Pilatus data (I mean *looking*)
When you are inspecting the images looking at them at 100% size is important: spots are small relative to pixels and the point spread is essentially zero. I also find it helpful to look at white spots on a black background rather than the reverse. The DECTRIS folks have an image viewer named ALBULA which works well, however ADXV also works fine (IMHO) if you tweak the settings as above. It is remarkable how big a difference it makes. The other big difference in terms of viewing the images is that (if you have low counts) you are actually at the mercy of real Poisson statistics. For example, if you have a "spot" (pixel) with 8 counts in against a background of 0 - 3 counts (say) it looks nice and clear - certainly based on experience of CCD images. And the spot is say four times the background so it must be good right? However the variance on a spot with 8 counts is 8, the variance from background subtraction may be about 3 so your spot has a maximum I/sigma of ~ 8 / sqrt(11) so about 2 and a bit. On the flip side, data from a decent crystal taken with a low dose can look almost blank at first glance (esp. with black spots on white; zoomed out) but process very nicely. Take some time to get used to the instrument. A couple of final comments: The machine has no read-out noise so fine phi slicing (and dose slicing) can only help - recording twice as many degrees with half as much dose increases the chance of getting a complete and relatively undamaged data set. All it does is take up lots of disk space. There is really no risk in doing this, unlike with a CCD where you are at war with the read-out noise. The machine also behaves completely differently to a CCD: this takes some getting used to. Take narrow oscillations as this will give better measurements of strong reflections (which I think is detailed in the papers Bob recommended.) Also *take your time* - one of the great things about these detectors is that they allow you to do continuous exposures, which can essentially double the throughput or more of data collection. Take back some of that time to use a lower dose rate and spread your photons out more evenly across reciprocal space. You can always measure more data if your sample is undamaged. Best wishes, Graeme On 7 May 2013 02:00, Robert Sweet <rsw...@bnl.gov> wrote: > The seminal paper on actually how to collect data from detectors like this > and others with negligible read-out time is this one, which I strongly > recommend: > > Optimal Fine phi-slicing for Single-Photon-Counting Pixel Detectors Marcus > Mueller, Meitian Wang, and Clemens Schulze-Briese, Acta Cryst.(2012) D68, > 42-56 > > And you can pick up a copy of the paper from the RapiData web site: > http://www.px.nsls.bnl.gov/courses/papers/Mueller_ACD68_2012.pdf > > > The classic paper on data-collection strategies is this: > > Data-Collection Stragegies, Dauter, Z. Acta Cryst. (1999). D55, 1703-1717. > > Also available from the RapiData site: > > http://www.px.nsls.bnl.gov/courses/papers/dauter_strategy.pdf > > > Then there are multiple papers on damage and its impact on your data. I > suggest this one: > > Radiation damage in macromolecular crystallography: what is it and why > should we care?, E.Garman, Acta Cryst. D66, 339-351(2010). > > which you can find here: > > http://www.px.nsls.bnl.gov/courses/papers/actad-garman-2010.pdf > > With this under your belt you'll be able to decide how to collect your > phasing data. The bottom line is probably that you should go for SAD data. > Employ multiple crystals and average them together in a judicious way, > keeping only the sweeps from barely damaged x-tals. > > Good luck, > > Bob Sweet > > ========================================================================= > Robert M. Sweet E-Dress: sw...@bnl.gov > Group Leader, PXRR: Macromolecular ^ (that's L > Crystallography Research Resource at NSLS not 1) > http://px.nsls.bnl.gov/ > Photon Sciences and Biosciences Dept > Office and mail, Bldg 745, a.k.a. LOB-5 > Brookhaven Nat'l Lab. Phones: > Upton, NY 11973 631 344 3401 (Office) > U.S.A. 631 344 2741 (Facsimile) > ========================================================================= > > > On Mon, 6 May 2013, Theresa Hsu wrote: > >> Dear crystallographers >> >> Is there a good source/review/software to obtain tips for good data >> collection strategy using PILATUS detectors at synchrotron? Do we need to >> collect sweeps of high and low resolution data separately? For anomalous >> phasing (MAD), does the order of wavelengths used affect structure solution >> or limit radiation damage? >> >> Thank you. >> >> Theresa >> >
