diff --git a/rtengine/imagedata.cc b/rtengine/imagedata.cc
index f3516e5a8..640eee96e 100644
--- a/rtengine/imagedata.cc
+++ b/rtengine/imagedata.cc
@@ -474,14 +474,14 @@ FrameData::FrameData (rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
 
 
     uint16 bitspersample = 0, samplesperpixel = 0, sampleformat = 0, photometric = 0, compression = 0;
-    rtexif::Tag* bps = frameRootDir->findTag("BitsPerSample");
-    rtexif::Tag* spp = frameRootDir->findTag("SamplesPerPixel");
-    rtexif::Tag* sf = frameRootDir->findTag("SampleFormat");
-    rtexif::Tag* pi = frameRootDir->findTag("PhotometricInterpretation");
-    rtexif::Tag* c = frameRootDir->findTag("Compression");
+    const rtexif::Tag* const bps = frameRootDir->findTag("BitsPerSample");
+    const rtexif::Tag* const spp = frameRootDir->findTag("SamplesPerPixel");
+    const rtexif::Tag* const sf = frameRootDir->findTag("SampleFormat");
+    const rtexif::Tag* const pi = frameRootDir->findTag("PhotometricInterpretation");
+    const rtexif::Tag* const c = frameRootDir->findTag("Compression");
 
     if (mnote && (!make.compare (0, 6, "PENTAX") || (!make.compare (0, 5, "RICOH") && !model.compare (0, 6, "PENTAX")))) {
-        rtexif::Tag* hdr = mnote->findTag("HDR");
+        const rtexif::Tag* const hdr = mnote->findTag("HDR");
         if (hdr) {
             if (hdr->toInt() > 0 && hdr->toInt(2) > 0) {
                 isHDR = true;
@@ -490,7 +490,7 @@ FrameData::FrameData (rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
 #endif
             }
         } else {
-            rtexif::Tag* dm = mnote->findTag("DriveMode");
+            const rtexif::Tag* const dm = mnote->findTag("DriveMode");
             if (dm) {
                 char buffer[60];
                 dm->toString(buffer, 3);
@@ -505,7 +505,7 @@ FrameData::FrameData (rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
         }
 
         if (!isHDR) {
-            rtexif::Tag* q = mnote->findTag("Quality");
+            const rtexif::Tag* const q = mnote->findTag("Quality");
             if (q && q->toInt() == 7) {
                 isPixelShift = true;
 #if PRINT_HDR_PS_DETECTION
@@ -530,7 +530,11 @@ FrameData::FrameData (rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
         sampleformat = sf->toInt();
     }
 
-    if ((!bps & !spp) || !pi) {
+    if (
+        !bps
+        || !spp
+        || !pi
+    ) {
         return;
     }
 
diff --git a/rtexif/rtexif.cc b/rtexif/rtexif.cc
index b6b5b55fe..a90ec18b5 100644
--- a/rtexif/rtexif.cc
+++ b/rtexif/rtexif.cc
@@ -1572,7 +1572,7 @@ double Tag::toDouble (int ofs) const
 /**
  * @brief Create an array of the elements
  */
-double *Tag::toDoubleArray (int ofs)
+double* Tag::toDoubleArray (int ofs) const
 {
     double *values = new double[count];
 
@@ -1583,7 +1583,7 @@ double *Tag::toDoubleArray (int ofs)
     return values;
 }
 
-void Tag::toRational (int& num, int& denom, int ofs)
+void Tag::toRational (int& num, int& denom, int ofs) const
 {
 
     switch (type) {
@@ -1632,7 +1632,7 @@ void Tag::toRational (int& num, int& denom, int ofs)
     }
 }
 
-void Tag::toString (char* buffer, int ofs)
+void Tag::toString (char* buffer, int ofs) const
 {
 
     if (type == UNDEFINED && !directory) {
diff --git a/rtexif/rtexif.h b/rtexif/rtexif.h
index 937945aac..822407389 100644
--- a/rtexif/rtexif.h
+++ b/rtexif/rtexif.h
@@ -282,9 +282,9 @@ public:
     int     toInt         (int ofs = 0, TagType astype = INVALID) const;
     void    fromInt       (int v);
     double  toDouble      (int ofs = 0) const;
-    double *toDoubleArray (int ofs = 0);
-    void    toRational    (int& num, int& denom, int ofs = 0);
-    void    toString      (char* buffer, int ofs = 0);
+    double* toDoubleArray (int ofs = 0) const;
+    void    toRational    (int& num, int& denom, int ofs = 0) const;
+    void    toString      (char* buffer, int ofs = 0) const;
     void    fromString    (const char* v, int size = -1);
     void    setInt        (int v, int ofs = 0, TagType astype = LONG);