speed.rst: Add a note about static detector geometry

1 files changed, 10 insertions, 0 deletions

diff --git a/doc/articles/speed.rst b/doc/articles/speed.rst
index f4c4808d..5b3a8fbd 100644
--- a/doc/articles/speed.rst
+++ b/doc/articles/speed.rst
@@ -127,3 +127,13 @@ you limit the resolution at the integration stage, the number of reflections to
 be integrated will be much smaller, which can lead to a significant speed
 improvement.  However, the ``--push-res`` value that you use for merging must
 be smaller than the value used for integration.
+
+
+Use a static detector geometry
+==============================
+
+CrystFEL geometry files allow some aspects of the geometry to come from the
+data files, such as the panel z-positions ("clen"/camera length) and overall
+detector shifts.  If you can instead give fixed numerical values for
+everything, then some parts of CrystFEL can prepare calculations in advance.
+In some cases, this can make a significant speed improvement.