Re: [ccp4bb] Effects of Multiplicity and Fine Phi with Equivalent Count Numbers

[Boaz Shaanan]

Hi Jacob, I may have missed completely your point but as far as my memory goes, the main argument in favour of fine slicing has always been reduction of the noise arising from incoherent scattering, which in the old days arose from the capillary, solvent, air, you name it. The noise reduction in fine slicing is achieved by shortening the exposure time per frame. This argument still holds today although the sources of incoherent scattering could be different. Of course, there are other reasons to go for fine slicing such as long axes and others. In any case it's the recommended method these days, and for good reasons, isn't it?   Best regards,                    Boaz   Boaz Shaanan, Ph.D.                                         Dept. of Life Sciences                                      Ben-Gurion University of the Negev                          Beer-Sheva 84105                                            Israel                                                                                                                  E-mail: bshaa...@bgu.ac.il Phone: 972-8-647-2220  Skype: boaz.shaanan                  Fax:   972-8-647-2992 or 972-8-646-1710                          From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Keller, Jacob [kell...@janelia.hhmi.org] Sent: Wednesday, November 30, 2016 11:37 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Effects of Multiplicity and Fine Phi with Equivalent Count Numbers Dear Crystallographers,   I am curious whether the observed effects of fine phi slicing might in part or in toto be due to simply higher “pseudo-multiplicity.” In other words, under normal experimental conditions, does simply increasing the number of measurements increase the signal and improve precision, even with the same number of total counts in the dataset?   As such, I am looking for a paper which, like Pflugrath’s 1999 paper, compares two data sets with equivalent total counts but, in this case, different multiplicities. For example, is a single sweep with 0.5 degree 60s exposures empirically, in real practice, equivalent statistically to six passes with 0.5 degree 10s frames? Better? Worse? Our home source has been donated away to Connecticut, so I can’t do this experiment myself anymore.   All the best,   Jacob Keller     ******************************************* Jacob Pearson Keller, PhD Research Scientist HHMI Janelia Research Campus / Looger lab Phone: (571)209-4000 x3159 Email: kell...@janelia.hhmi.org *******************************************