diff --git a/common/Reflection.h b/common/Reflection.h
index 03517ee1..7d5b009c 100644
--- a/common/Reflection.h
+++ b/common/Reflection.h
@@ -13,7 +13,7 @@ struct Reflection {
     int64_t k;
     int64_t l;
     float image_number; // Can be in-between for 3D integration
-    float angle_deg; // phi angle from XDS
+    float delta_phi; // phi angle from XDS - difference from middle of current frame (NOT an absolute angle)
     float predicted_x;
     float predicted_y;
     float d;
diff --git a/frame_serialize/CBORStream2Deserializer.cpp b/frame_serialize/CBORStream2Deserializer.cpp
index 7285d712..52748861 100644
--- a/frame_serialize/CBORStream2Deserializer.cpp
+++ b/frame_serialize/CBORStream2Deserializer.cpp
@@ -449,6 +449,8 @@ namespace {
                 r.k = GetCBORInt(map_value);
             else if (key == "l")
                 r.l = GetCBORInt(map_value);
+            else if (key == "phi")
+                r.delta_phi = GetCBORFloat(map_value);
             else if (key == "x")
                 r.predicted_x = GetCBORFloat(map_value);
             else if (key == "y")
diff --git a/frame_serialize/CBORStream2Serializer.cpp b/frame_serialize/CBORStream2Serializer.cpp
index e3c47f89..b07b5879 100644
--- a/frame_serialize/CBORStream2Serializer.cpp
+++ b/frame_serialize/CBORStream2Serializer.cpp
@@ -235,6 +235,7 @@ inline void CBOR_ENC(CborEncoder &encoder, const Reflection& r) {
     CBOR_ENC(mapEncoder, "h", r.h);
     CBOR_ENC(mapEncoder, "k", r.k);
     CBOR_ENC(mapEncoder, "l", r.l);
+    CBOR_ENC(mapEncoder, "phi", r.delta_phi);
     CBOR_ENC(mapEncoder, "x", r.predicted_x);
     CBOR_ENC(mapEncoder, "y", r.predicted_y);
     CBOR_ENC(mapEncoder, "d", r.d);
diff --git a/image_analysis/bragg_prediction/BraggPredictionRot.cpp b/image_analysis/bragg_prediction/BraggPredictionRot.cpp
index 6f142cb3..453e4844 100644
--- a/image_analysis/bragg_prediction/BraggPredictionRot.cpp
+++ b/image_analysis/bragg_prediction/BraggPredictionRot.cpp
@@ -135,6 +135,7 @@ int BraggPredictionRot::Calc(const DiffractionExperiment &experiment, const Crys
                         .h = h,
                         .k = k,
                         .l = l,
+                        .delta_phi = phi * 180.0f / static_cast<float>(M_PI),
                         .predicted_x = x,
                         .predicted_y = y,
                         .d = d,
diff --git a/image_analysis/bragg_prediction/BraggPredictionRotGPU.cu b/image_analysis/bragg_prediction/BraggPredictionRotGPU.cu
index 8363d780..8af6bb47 100644
--- a/image_analysis/bragg_prediction/BraggPredictionRotGPU.cu
+++ b/image_analysis/bragg_prediction/BraggPredictionRotGPU.cu
@@ -150,6 +150,7 @@ namespace {
             out[count].h = h;
             out[count].k = k;
             out[count].l = l;
+            out[count].delta_phi = phi;
             out[count].predicted_x = x;
             out[count].predicted_y = y;
             out[count].d = 1.0f / sqrtf(p0_sq);
diff --git a/tools/jfjoch_extract_hkl.cpp b/tools/jfjoch_extract_hkl.cpp
index f12412e7..951be721 100644
--- a/tools/jfjoch_extract_hkl.cpp
+++ b/tools/jfjoch_extract_hkl.cpp
@@ -157,7 +157,7 @@ int main(int argc, char **argv) {
                     if (dist < max_dist_ewald_sphere)
                         f << r.l << " " << r.k << " " << r.h << " "
                                 << r.I << " " << r.sigma << " " << dist << " "
-                                << r.predicted_x << " " << r.predicted_y << " " << r.angle_deg
+                                << r.predicted_x << " " << r.predicted_y << " " << r.delta_phi
                                 << std::endl;
                 }
             }
diff --git a/writer/HDF5DataFilePluginReflection.cpp b/writer/HDF5DataFilePluginReflection.cpp
index 8f826b29..53c3545e 100644
--- a/writer/HDF5DataFilePluginReflection.cpp
+++ b/writer/HDF5DataFilePluginReflection.cpp
@@ -17,7 +17,7 @@ void HDF5DataFilePluginReflection::Write(const DataMessage &msg, uint64_t image_
 
     std::vector<int32_t> h, k, l;
     std::vector<float> I, sigma, d, lp;
-    std::vector<float> image, pred_x, pred_y, bkg, partiality;
+    std::vector<float> image, phi, pred_x, pred_y, bkg, partiality;
 
     for (const auto &refl : msg.reflections) {
         image.emplace_back(refl.image_number);
@@ -32,6 +32,7 @@ void HDF5DataFilePluginReflection::Write(const DataMessage &msg, uint64_t image_
         bkg.emplace_back(refl.bkg);
         lp.emplace_back(1.0/refl.rlp);
         partiality.emplace_back(refl.partiality);
+        phi.emplace_back(refl.delta_phi);
     }
 
     std::string image_group_name = fmt::format("image_{:06d}", image_number);
@@ -41,6 +42,7 @@ void HDF5DataFilePluginReflection::Write(const DataMessage &msg, uint64_t image_
     image_group.SaveVector("k", k);
     image_group.SaveVector("l", l);
     image_group.SaveVector("d", d)->Units("Angstrom");
+    image_group.SaveVector("delta_phi", phi);
     image_group.SaveVector("predicted_x", pred_x);
     image_group.SaveVector("predicted_y", pred_y);
     image_group.SaveVector("int_sum", I);