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authorThomas White <taw@physics.org>2014-11-27 15:12:31 +0100
committerThomas White <taw@physics.org>2014-11-27 15:12:31 +0100
commitb7a7008b8236a2035241935d1276e7113d1fc82c (patch)
treef21a80b3332c9956c8de1ae8e4abe297351bcd5d
parent53296b684bf2b3b37b2bb4b92e805445a0428179 (diff)
Fix pre-merging Poisson error calculation for low photon counts
-rw-r--r--libcrystfel/src/integration.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/libcrystfel/src/integration.c b/libcrystfel/src/integration.c
index 4edc0c56..edc6e7eb 100644
--- a/libcrystfel/src/integration.c
+++ b/libcrystfel/src/integration.c
@@ -1633,9 +1633,10 @@ static void integrate_rings_once(Reflection *refl, struct image *image,
sig2_poisson = aduph * intensity;
/* If intensity is within one photon of nothing, set the Poisson
- * error to be one photon */
+ * error to be one photon. Pretend I = 1 photon = 1*aduph,
+ * then sig2_posson = aduph*intensity = aduph^2. */
if ( fabs(intensity / aduph) < 1.0 ) {
- sig2_poisson = aduph;
+ sig2_poisson = aduph * aduph;
}
/* If intensity is negative by more than one photon, assume that