diff --git a/src/advanced_dialog.cpp b/src/advanced_dialog.cpp
index 34878fba1..2e2c54d96 100644
--- a/src/advanced_dialog.cpp
+++ b/src/advanced_dialog.cpp
@@ -592,6 +592,20 @@ double AdvancedDialog::DetermineGuideSpeed()
     }
     return sidRate;
 }
+
+// Floating point equality comparisons can be a problem due to rounding and trivial inequalities.
+// PercentChange can be used to see if a change is worth reacting to
+double AdvancedDialog::PercentChange(double oldVal, double newVal)
+{
+    double chg;
+    if (fabs(oldVal) < 0.0001)
+    {
+        return 100. * newVal; // not meaningful, but avoids divide by zero
+    }
+    else
+        return 100. * fabs(1. - newVal / oldVal);
+}
+
 // Reacts to param changes in the AD that change the image scale.  Calibration step-size is recalculated, calibration is
 // cleared, MinMoves are set to defaults based on new image scale
 void AdvancedDialog::MakeImageScaleAdjustments()
diff --git a/src/advanced_dialog.h b/src/advanced_dialog.h
index 18fae66eb..2affbfaa1 100644
--- a/src/advanced_dialog.h
+++ b/src/advanced_dialog.h
@@ -103,6 +103,7 @@ class AdvancedDialog : public wxDialog
 
     bool Validate() override;
     void ShowInvalid(wxWindow *ctrl, const wxString& message);
+    double PercentChange(double oldVal, double newVal);
     void FlagImageScaleChange()
     {
         m_imageScaleChanged = true;
diff --git a/src/camera.cpp b/src/camera.cpp
index 16061c4f5..5948df1da 100644
--- a/src/camera.cpp
+++ b/src/camera.cpp
@@ -1247,7 +1247,10 @@ void CameraConfigDialogCtrlSet::UnloadValues()
 
     double oldPxSz = m_pCamera->GetCameraPixelSize();
     double newPxSz = m_pPixelSize->GetValue();
-    if (oldPxSz != newPxSz)
+    if (oldPxSz != newPxSz &&
+        pFrame->pAdvancedDialog->PercentChange(oldPxSz, newPxSz) >
+            5.0) // Avoid rounding problems with floating point equality test; don't clear
+                 // calibration for inconsequential changes
         pFrame->pAdvancedDialog->FlagImageScaleChange();
     m_pCamera->SetCameraPixelSize(m_pPixelSize->GetValue());
 
diff --git a/src/myframe.cpp b/src/myframe.cpp
index e926e5fd0..955dc2af5 100644
--- a/src/myframe.cpp
+++ b/src/myframe.cpp
@@ -3327,8 +3327,9 @@ void MyFrameConfigDialogCtrlSet::UnloadValues()
                                        m_varExpDelayLong->GetValue() * 1000);
         int oldFL = m_pFrame->GetFocalLength();
         int newFL = GetFocalLength(); // From UI control
-        if (oldFL != newFL) // Validator insures fl is generally reasonable and non-zero
-            m_pFrame->pAdvancedDialog->FlagImageScaleChange();
+        if (oldFL != newFL) // Validator insures fl is generally reasonable and non-zero; don't react to trivial changes
+            if (m_pFrame->pAdvancedDialog->PercentChange(oldFL, newFL) > 5.0)
+                m_pFrame->pAdvancedDialog->FlagImageScaleChange();
         m_pFrame->SetFocalLength(GetFocalLength());
 
         int idx = m_pLanguage->GetSelection();