diff --git a/tools/jfjoch_process.cpp b/tools/jfjoch_process.cpp
index 54660d95..6b0dea09 100644
--- a/tools/jfjoch_process.cpp
+++ b/tools/jfjoch_process.cpp
@@ -21,6 +21,10 @@
 // Default rot3d per-frame scale-G smoothing range (XDS DELPHI-like), in degrees of rotation.
 constexpr double SMOOTH_G_DEFAULT_DEG = 5.0;
 
+// Default rot3d per-observation merge outlier rejection (sigma from the per-reflection median, XDS-like).
+// Neutral-or-better across the test crystals; pass --reject-outliers 0 to disable.
+constexpr double REJECT_OUTLIERS_DEFAULT_NSIGMA = 6.0;
+
 void print_usage() {
     std::cout << "Usage jfjoch_process {<options>} <input.h5>" << std::endl;
     std::cout << "Options:" << std::endl;
@@ -66,7 +70,7 @@ void print_usage() {
     std::cout << "   --min-partiality <num>          Minimum partiality to accept reflection (default: 0.02)" << std::endl;
     std::cout << "   --capture-uncertainty <num>     rot3d: systematic sigma ~num*(1-captured_fraction)*I on under-captured fulls (default: 1.0 for rot3d, 0 otherwise)" << std::endl;
     std::cout << "   --mosaicity <num>               Diagnostic: fix the scaling mosaicity (deg) instead of the per-image seed" << std::endl;
-    std::cout << "   --reject-outliers <num>         Per-observation merge outlier rejection, N sigma from the per-reflection median (default: off; e.g. 6, XDS/DIALS-style)" << std::endl;
+    std::cout << "   --reject-outliers <num>         Per-observation merge outlier rejection, N sigma from the per-reflection median (default: 6 for rot3d, XDS/DIALS-style; 0 = off)" << std::endl;
     std::cout << "   --reject-delta-cchalf <num>     Per-crystal CC1/2-delta rejection: drop images with deltaCChalf below mean - N*stddev (default: off; e.g. 2.5)" << std::endl;
     std::cout << "   --min-image-cc <num>            Per-image CC limit in percent (default: no limit)" << std::endl;
     std::cout << "   --scaling-iterations <num>      Number of scaling iterations with no reference data (default: 3)" << std::endl;
@@ -785,8 +789,8 @@ int main(int argc, char **argv) {
     scaling_settings.CaptureUncertaintyCoeff(capture_uncertainty_arg.value_or(combine_3d ? 1.0 : 0.0));
     scaling_settings.ForcedMosaicity(forced_mosaicity_arg);
     scaling_settings.MinCCForImage(min_image_cc / 100.0);   // --min-image-cc is in percent; the setting is a fraction
-    if (outlier_reject_nsigma)
-        scaling_settings.OutlierRejectNsigma(*outlier_reject_nsigma);
+    scaling_settings.OutlierRejectNsigma(
+        outlier_reject_nsigma.value_or(combine_3d ? REJECT_OUTLIERS_DEFAULT_NSIGMA : 0.0));
     scaling_settings.FileFormat(intensity_format);
 
     experiment.ImportScalingSettings(scaling_settings);