Looking at PAD images is something we have had to get used to at Diamond, and sometimes it takes some tweaking to get a really good idea of what the images actually look like. This is a challenge if you measure the data properly with fine slicing & low dose...
One thing which really helps is to have the positive image rather than the negative i.e. white spots on a dark background. The eye is much better at picking these out. There are also tweaks which can be done within image viewers to make spots more visible for example showing the maximum rather than average of an n x n zoomed out image. ADXV white on black background + 100% scale generally works well. Summing the images using e.g. XDS merge2cbf or dials.merge_cbf can make them easier to interpret, particularly if you're used to looking at 1 degree CCD images. Within dials (http://dials.sf.net) we have an image viewer, dials.image_viewer, which also has the option to calculate local mean, variance, dispersion and so on so you can see "what the spot finding sees" - this can make a massive difference. For example: Default image http://www.ccp4.ac.uk/xia/screenshots/Screen%20Shot%202015-04-28%20at%2008.01.34.png Tweaked to "inverse" i.e. right way around, brightness turned down: http://www.ccp4.ac.uk/xia/screenshots/Screen%20Shot%202015-04-28%20at%2008.01.52.png - much better - but then the dispersion map thresholded a la spot finding: http://www.ccp4.ac.uk/xia/screenshots/Screen%20Shot%202015-04-28%20at%2008.02.06.png This really shows the images well... also allows you to tweak the spot finding settings nicely. This is a particular problem with good crystals from a good beamline as the spots can often be 1 or 2 pixels with many many counts on a background of very small (often 0) counts. A final challenge with these detectors is that they *actually count photons* i.e. the statistics are the same as counting cars going past the school* - where on a CCD if you can *see* a spot there is a spot there, as it's climbed out through the readout noise etc, on a PAD you need to look at the numbers and by and large put more faith in the processing software than your eyes, as people are great at finding patterns where no patterns are there to be found. Flip side is yes, the images are harder to interpret but these detectors do a nice job of actually recording diffraction! best wishes Graeme ------------------------------------- *other elementary examples exist. On Tue, Apr 28, 2015 at 3:08 AM Jens Kaiser <kai...@caltech.edu> wrote: > SSRL Bluice opens the image in adxv upon double click in the diffraction > window. > > HTH, > > Jens > > On Mon, 2015-04-27 at 16:57 -0700, Bernhard Rupp (Hofkristallrat a.D.) > wrote: > > Thanks - particularly great if we had these images/option available to > look > > at > > in real time during data collection, w/o first having to download the raw > > data (not > > really feasible during remote data collection). I don't think the ESRF > > online data base has the option, but other beam lines may? > > > > Thx, BR > > > > -----Original Message----- > > From: James Holton [mailto:jmhol...@lbl.gov] > > Sent: Monday, April 27, 2015 4:05 PM > > To: b...@hofkristallamt.org; CCP4BB@JISCMAIL.AC.UK > > Subject: Re: [ccp4bb] PAD images > > > > > > In the ADXV viewer: > > http://www.scripps.edu/tainer/arvai/adxv.html > > > > Go to Edit:Settings and click on the "Small Spots" radio button. This > solves > > most of the "I can't interpret the spots" problems you describe. > > > > -James Holton > > MAD Scientist > > > > On 4/27/2015 3:31 PM, Bernhard Rupp (Hofkristallrat a.D.) wrote: > > > Hi Fellows, > > > > > > I wonder whether it's just me and my eyesight failing (or excessive > > > internal lubrication).... > > > > > > It seems that the art of looking at diffraction patterns and being > > > able to tell a lot about modulation, superstructures, extinctions, > > > etc. becomes kind of useless old fart stuff when dealing with PAD > > > images. I can't for my life see interpretable patterns on frames > > > where the beamline autoprocessing delivers actual data sets. The > > > absence of a point spread function etc that gave interpretable > > > film-like images on IPs or CCDs, seems to be the reason. > > > > > > A PAD pixel with 1000000 counts looks like one with 100 when viewed > > > with the low dynamic range of the displays compared to the huge > > > dynamic range of the detector. > > > > > > Is there somewhere in the process a humanly unusable composite image > > > with a point spread that allows visual pre-processing, inspection, and > > > interpretation despite a low dynamic display range? > > > > > > Looking at the hklview or similar after processing is pointless (no > > > pun intended), because the stuff I might be interested in is already > > > processed away. > > > > > > Some humanly interpretable raw data images would be quite useful... > > > > > > Best regards, BR > > > ----------------------------------------------------------------- > > > Bernhard Rupp > > > 001 (925) 209-7429 > > > +43 (676) 571-0536 > > > b...@ruppweb.org > > > http://www.ruppweb.org/ > > > ----------------------------------------------------------------- > > > The man who follows the crowd will get no further than the crowd. > > > The man who walks alone will find himself in places where no one has > > > been before. > > > ----------------------------------------------------------------- >
