Update simulation details

1 files changed, 3 insertions, 1 deletions

diff --git a/src/pattern_sim.c b/src/pattern_sim.c
index d076eb7f..9a00b5d7 100644
--- a/src/pattern_sim.c
+++ b/src/pattern_sim.c
@@ -99,7 +99,9 @@ static void show_details()
 " S = solid angle of corresponding pixel\n"
 "\n"
 "Poisson counts are generated from the expected intensities using Knuth's\n"
-"algorithm.\n"
+"algorithm.  When the intensity is sufficiently high that Knuth's algorithm\n"
+"would result in machine precision problems, a normal distribution with\n"
+"standard deviation sqrt(I) is used instead.\n"
 "\n"
 "Bloom of the CCD is included.  Any excess intensity in a particular pixel\n"
 "is divided between the neighbouring pixels.  Diagonal neighbours receive\n"