Mark J. van Raaij wrote:
On a related note, how to refine a structure with only 5000
reflections, which could happen when you have a small a.u. and modest
resolution? Could, exceptionally, a lower absolute amount of
reflections be used for Rfree, say 500?
Eleanor (mostly) answered my identical question a few years ago: the
answer was, what matters (mostly) is that the sigmaA estimation (which
uses the free reflections) is well conditioned, and the program authors
have gone to some lengths to make it so for as few as 100 reflections.
For those dodgy cases, that is; in general, you do want more (1000-1500).
It's when the program starts complaining that you know you're in trouble.
....
At least, that's how I remember the answer. I cannot tell exactly,
because I cannot find the archive posting. In fact, after googling,
ccp4bb-archiving, and generally poking, I'm still very much not sure
whether a comprehensive ccp4 archive exists anywhere. Please say it
ain't so....? *whimper*
