Re: [Imgcif-l] question on beam center

["Herbert J. Bernstein" <yaya@bernstein-plus-sons.com>]

As long as there is a clear and consistent definition, either will work,
i.e. either using the pixel origin for the bins or defining a new
origin for bins.  I would appreciate hearing from others on the list
as to which one would be easier for them to work with. -- Herbert


At 12:41 AM +0200 10/16/07, Jon Wright wrote:
>Dear Herbert,
>
>The fast/slow/units seems like a good solution. Is there some reason for
>this choice of definition?
>
>    ... In all cases the
>    center distances are measured from the center of the
>    first pixel, i.e. in a 2x2 binning, the measuring origin
>    is offset from the centers of the bins by one half pixel
>    towards the first pixel.
>
>Why not measure from the centre of the bins in the case of bins?
>
>Best,
>
>Jon
>
>
>
>
>
>Herbert J. Bernstein wrote:
>>  Dear Miro,
>>
>>      The problem is not what I like, but what processing programs can
>>  deal with.  In the last round of proposed dictionary changes, we
>>  suggested:
>>
>>  # _diffrn_data_frame.center_fast
>>  # _diffrn_data_frame.center_slow
>>  # _diffrn_data_frame.center_units
>>
>>  which would allow you to specify the center in mm, pixels or bins.
>>  What we need now is general agreement on this approach.
>>
>>      I am forwarding this message to the imgcif list to see if anyone
>>  objects.
>>
>>      Regards,
>>        Herbert
>>
>>
>>
>>  At 6:54 PM +0200 10/15/07, Miroslav Kobas wrote:
>>>  Dear Herbert,
>>>
>>>  I think that Andy Arvai has already contacted you concerning this
>>>  topic. It is about the fullCBF header. I have made a recent dataset
>>>  available on our webpage (<http://pilatus.web.psi.ch/datasets.htm>
>>>  http://pilatus.web.psi.ch/datasets.htm) with the miniCBF and the
>>>  fullCBF header (conversion done with convert_minicbf). After
>>>  experiencing some problems with adxv, I asked Andy, Harry Powell,
>>>  Jim Pflugrath to adapt their programs such that they take all the
>>>  necessary information from the CBFheader.
>>>
>>>  Andy had problems with the definition of coordinate systems and how
>>>  to get the beam center (units of mm) into a know coordinate system
>>>  (in units of pixels).
>>>
>>>  These are the 3 lines defining the beam center in units of mm in the
>>>  full CBF header:
>>>  _diffrn_data_frame.center_slow 225.406000
>>>  _diffrn_data_frame.center_fast -211.577200
>>>  _diffrn_data_frame.center_units mm
>>>
>>>  For our detector, they correspond to the following beam center in
>>>  units of pixels:
>>>  slow 225.406000 corresponds to y at 1310.50
>>>  fast -211.577200 corresponds to x at 1230.10
>>>
>>>  This conversion can only be done, if one understands the definition
>>>  of coordinate systems properly. I have asked several people who have
>>>  experience with CBF if they understand how the coordinate systems
>>>  are defined, but they could no give me a unified solution.
>>>
>>>  Andy has asked me to include the following lines in our header:
>>>  _diffrn_data_frame.adxv_beam_center_x 2463
>>>  _diffrn_data_frame.adxv_beam_center_y 2527
>>>
>>>  But since we really head now for the standard, full CBF-header (Eric
>>>  is implementing the full CBF-header into our dataformat), we only
>>>  want to use items, which are defined therein. Therefor I have
>>>  suggested Andy to ask you, if it would be possible to add 2 more
>>>  items in the CBF header giving the beam center in x and y. Something
>>>  like:
>>>  _diffrn_data_frame.beam_center_x 2463
>>>  _diffrn_data_frame.beam_center_y 2527
>>>
>>>  What do you think about that? The consequence would be that there
>>>  would also be changes in convert_minicbf and and in our header
>>>  structure. Eric has told me that it is not a problem for him to
>>>  include additional items in our header. But I would easily
>>>  understand that you would not like to include these items in the
>>>  full CBF header, since this information is already there in a
>  >> slightly different form.
>>>
>>>  If you want to check the above values, I have attached you one of
>>>  our recent images with the full CBF-header.
>>>
>>>  Thanks for everything and have a nice day.
>>>  kind regards
>>>  miro
>>>
>>>  --
>>>  ________________________________________
>>>  Dr. Miroslav Kobas
>>>  DECTRIS Ltd.
>>>  OSRA 007
>>>  5232 Villigen PSI
>>>  Switzerland
>>>
>>>  <mailto:miroslav.kobas@dectris.com>miroslav.kobas@dectris.com
>>>  <http://www.dectris.com>http://www.dectris.com
>>>  <http://pilatus.web.psi.ch>http://pilatus.web.psi.ch
>>>  +41 56 310 3269 phone
>>>  +41 56 310 5454 fax
>>>  ________________________________________
>>>
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>>>  filename="run2_1_FH_00001.cbf";
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>>>  X-Attachment-Id: f_f7t7fn8h
>>>
>>>  Attachment converted: Macintosh HD:run2_1_FH_00001.cbf (    / 
>>>) (001C5C25)
>>
>>
>
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-- 
=====================================================
  Herbert J. Bernstein, Professor of Computer Science
    Dowling College, Kramer Science Center, KSC 121
         Idle Hour Blvd, Oakdale, NY, 11769

                  +1-631-244-3035
                  yaya@dowling.edu
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