Improve focus distance precision for Nikon Z

Exiv2 · Aug 8, 2023 · 2a02539 · 2a02539
1 parent 6ea6e2c
commit 2a02539
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Showing 3 changed files with 17 additions and 3 deletions.
diff --git a/src/nikonmn_int.cpp b/src/nikonmn_int.cpp
@@ -1719,8 +1719,8 @@ constexpr TagInfo Nikon3MakerNote::tagInfoLd4_[] = {
      printApertureLd4},
     {60, "FocalLength2", N_("Focal Length 2"), N_("Focal length 2"), IfdId::nikonLd4Id, SectionId::makerTags,
      unsignedShort, 1, printFocalLd4},
-    {79, "FocusDistance2", N_("Focus Distance 2"), N_("Focus distance 2"), IfdId::nikonLd4Id, SectionId::makerTags,
-     unsignedByte, 1, printFocusDistance},
+    {78, "FocusDistance2", N_("Focus Distance 2"), N_("Focus distance 2"), IfdId::nikonLd4Id, SectionId::makerTags,
+     unsignedShort, 1, printFocusDistanceLd4},
     // End of list marker
     {0xffff, "(UnknownNikonLd4Tag)", "(UnknownNikonLd4Tag)", N_("Unknown Nikon Lens Data 3 Tag"), IfdId::nikonLd4Id,
      SectionId::makerTags, unsignedByte, 1, printValue},
@@ -3963,4 +3963,16 @@ std::ostream& Nikon3MakerNote::printFocalLd4(std::ostream& os, const Value& valu
   return os;
 }
 
+std::ostream& Nikon3MakerNote::printFocusDistanceLd4(std::ostream& os, const Value& value, const ExifData*) {
+  if (value.count() != 1 || value.typeId() != unsignedShort) {
+    return os << "(" << value << ")";
+  }
+  double dist = 0.01 * pow(10.0, (value.toInt64() / 256.0) / 40.0);
+  std::ostringstream oss;
+  oss.copyfmt(os);
+  os << std::fixed << std::setprecision(2) << dist << " m";
+  os.copyfmt(oss);
+  return os;
+}
+
 }  // namespace Exiv2::Internal
diff --git a/src/nikonmn_int.hpp b/src/nikonmn_int.hpp
@@ -173,6 +173,8 @@ class Nikon3MakerNote {
   static std::ostream& printLensId4ZMount(std::ostream& os, const Value& value, const ExifData*);
   //! Print focus distance
   static std::ostream& printFocusDistance(std::ostream& os, const Value& value, const ExifData*);
+  //! Print focus distance for new LensData as used for e.g. Nikon Z 6/7
+  static std::ostream& printFocusDistanceLd4(std::ostream& os, const Value& value, const ExifData*);
   //! Print lens aperture value
   static std::ostream& printAperture(std::ostream& os, const Value& value, const ExifData*);
   //! Print lens aperture value for new LensData as used for e.g. Nikon Z 6/7

diff --git a/test/data/test_reference_files/CH0_0174.exv.out b/test/data/test_reference_files/CH0_0174.exv.out
@@ -116,7 +116,7 @@ Exif.NikonLd4.LensID                         Short       1  0  0
 Exif.NikonLd4.MaxAperture                    Short       1  0  F0.5
 Exif.NikonLd4.FNumber                        Short       1  0  F0.5
 Exif.NikonLd4.FocalLength2                   Short       1  0  0 mm
-Exif.NikonLd4.FocusDistance2                 Byte        1  0  0.01 m
+Exif.NikonLd4.FocusDistance2                 Short       1  0  0.01 m
 Exif.Nikon3.RawImageCenter                   Short       2  2274 1515  2274 1515
 Exif.Nikon3.RetouchHistory                   Short      10  0 0 0 0 0 0 0 0 0 0  None
 Exif.Nikon3.ShutterCount                     Long        1  174  174