diff --git a/interfaces/Fingerprintd-Engine.cppm b/interfaces/Fingerprintd-Engine.cppm
index 46e3870..45e6c51 100644
--- a/interfaces/Fingerprintd-Engine.cppm
+++ b/interfaces/Fingerprintd-Engine.cppm
@@ -42,9 +42,21 @@ export namespace fingerprintd::engine {
     class Baseline {
     public:
         static constexpr std::size_t DefaultSamples = 5;
-        // A finger reads roughly 2.6x the floor; 2x separates them with margin
-        // on both measured runs.
-        static constexpr std::int32_t Multiplier = 2;
+
+        // A finger at full contact reads ~2.7x the floor (133 idle, 355-375
+        // pressed), so 2x separated them with margin. But 2x also discards the
+        // LANDING frames -- measured at 209 and 247 against a 133 floor, with
+        // the interrupt already asserted -- and those are the only frames a
+        // quick tap has to spare: a frame that detects a finger takes 400-580 ms
+        // to process (the trustlet's REPORT_EVENT is ~300 ms of it) while a tap
+        // lasts 400-600 ms, so detection one frame earlier is the difference
+        // between one image and two.
+        //
+        // 3/2 puts the threshold at 200 for a 133 floor: above the highest idle
+        // drift observed (147) and below the lowest landing frame seen (209).
+        // Expressed as a ratio because the floor is calibrated per session.
+        static constexpr std::int32_t MultiplierNum = 3;
+        static constexpr std::int32_t MultiplierDen = 2;
 
         explicit Baseline(std::size_t samples = DefaultSamples) : want_(samples) {}
 
@@ -59,7 +71,7 @@ export namespace fingerprintd::engine {
 
         bool Ready() const { return seen_ >= want_ && floor_ > 0; }
         std::int32_t Floor() const { return floor_; }
-        std::int32_t Threshold() const { return floor_ * Multiplier; }
+        std::int32_t Threshold() const { return floor_ * MultiplierNum / MultiplierDen; }
 
         // Nothing is a finger until the floor is known. An uncalibrated
         // Baseline reports false for everything rather than inventing a
diff --git a/tests/Engine/main.cpp b/tests/Engine/main.cpp
index e56b2cc..c108ebc 100644
--- a/tests/Engine/main.cpp
+++ b/tests/Engine/main.cpp
@@ -71,21 +71,28 @@ int main() {
         Check(!b.Ready(), "uncalibrated");
         Check(!b.IsFinger(1000000), "an uncalibrated baseline calls nothing a finger");
 
-        for (int i = 0; i < 5; i++) b.Observe(132);
+        for (int i = 0; i < 5; i++) b.Observe(133);
         Check(b.Ready(), "calibrated after five idle samples");
-        Check(b.Floor() == 132, "floor");
-        Check(b.Threshold() == 264, "threshold is 2x the floor");
+        Check(b.Floor() == 133, "floor");
+        Check(b.Threshold() == 199, "threshold is 1.5x the floor");
 
-        // The real measurement: idle 132-133, finger 345-366.
+        // The real measurement: idle 133 with drift to 147, landing frames
+        // 209-247, full contact 355-375. The threshold has to sit between the
+        // drift and the landing frames -- catching a landing frame is the only
+        // way a quick tap gets a second image.
         Check(!b.IsFinger(133), "an idle frame is not a finger");
-        Check(b.IsFinger(345) && b.IsFinger(366), "a pressed frame is");
+        Check(!b.IsFinger(147), "the highest observed idle drift is not a finger");
+        Check(b.IsFinger(209), "a LANDING frame is a finger (2x would have missed it)");
+        Check(b.IsFinger(247), "so is a partial-contact frame");
+        Check(b.IsFinger(355) && b.IsFinger(375), "full contact certainly is");
+        Check(133 * 2 > 247, "2x would have discarded both landing frames");
 
         // The floor is the max of the idle samples. A drifting idle must not
         // become a false finger.
         Baseline drift;
         for (std::int32_t m : {18, 20, 22, 24, 26}) drift.Observe(m);
         Check(drift.Floor() == 26, "floor takes the maximum, not the first sample");
-        Check(!drift.IsFinger(24), "drift within the idle range is not a finger");
+        Check(!drift.IsFinger(26), "drift within the idle range is not a finger");
 
         // Extra samples after calibration do not move it.
         Baseline fixed;