Dear JPK,
if I understand you correctly, you understand wrongly.
Integration programs for macromolecular data make use of profile fitting,
although you can switch this off, if you like.
The types of profile depend on the software. XDS fits 3D Gaussians after the
detector surface is projeced into reciprocal space. Wolfgang Kabsch stated in
one of his 1980s papers, that the profiles are more uniform after projection.
This observation has recently been "re-invented" by a group at the SNS in Oak
Ridge working on integration programs for they neutron instrument.
mosflm uses arbitrary profiles on the detector surface, created from strong
spots.
If you want to go very fancy, you can also use evalccd. As far as I
understand, the profiles are estimated from a ray tracing approach.
Best,
Tim
On Wednesday, February 10, 2016 02:24:25 PM Keller, Jacob wrote:
> Dear Crystallographers,
>
> As I understand it, all integration software uses measured intensities
> rather than fits thereof. Wouldn't it be better in the case of (very) fine
> phi slicing to start using 3D gaussian fits to the spots, perhaps even with
> outlier rejection? I would think a fit to, say, 10 samples of a Gaussian
> would be more precise than summing the intensities.
>
> Perhaps a lot of datasets have non-Gaussian distribution?
>
> JPK
>
> *******************************************
> Jacob Pearson Keller, PhD
> Looger Lab/HHMI Janelia Research Campus
> 19700 Helix Dr, Ashburn, VA 20147
> email: [log in to unmask]
> *******************************************
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