Hi, I sense a misunderstanding:
Cell parameters are not relevant when scaling together datasets: what
matters are intensities and (depending on algorithm) directional cosines
and the like.
Cell parameters are relevant, along with the other experimental
parameters, for knowing where to pick the intensities off the images
("integrating"). What denzo & scalepack do (which I suspect you're
referring to) is to split this into separate actions: denzo integrates,
and scalepack postrefines, meaning it optimizes the integrated
intensities by simultaneously taking into account experimental
parameters over whole dataset. Only then does it scale.
Xscale and Scala trust the intensities and only scale.
Yes, the cell parameters are also an indicator that you may have
non-isomorphism, but only that; it's the *intensities* where this is
manifested. So you could have "different" cells yet still perfectly
isomorphous intensities; or "same" cells and terrible non-isomorphism.
phx.
On 25/04/2010 16:05, Peter Grey wrote:
Dear Fred and Phil,
However there is no refinement of these parameters in XSCALE so if you
need to scale together several crystals (e.g. very small crystals that
show severe radiation damage after a few degrees) you end up with a
sub-optimal combined dataset after XSCALE. I thought SCALA can take
care of that and define cell parameters that fit best all data as
scalepack does when it considers all separate frames , from all
crystals where-as the input to XSCALE is not separate frames but
complete datasets).
Peter.
On Sun, Apr 25, 2010 at 12:14 PM, Frederic VELLIEUX
<frederic.velli...@orange.fr <mailto:frederic.velli...@orange.fr>> wrote:
Hi Phil,
Indeed it does, both during integration (INTEGRATE, only if you
"ask for it" with the proper keyword) and in the post-refinement
step (CORRECT). Normally this should be quite sufficient. I
haven't seen a single case where this was not sufficient.
Fred.
> Message du 25/04/10 09:55
> De : "Phil Evans"
> A : CCP4BB@JISCMAIL.AC.UK <mailto:CCP4BB@JISCMAIL.AC.UK>
> Copie à :
> Objet : Re: [ccp4bb] SUMMARY: scala and xds data
>
>
> Just to point out that Scala does not refine cell
parameters: I believe XDS does
>
> Phil
--
Peter
