diff --git a/.gitignore b/.gitignore
index f041276..1404b35 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 [bB]uild/
+.DS_Store
 
 # CMake files
 CMakeFiles/
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 314d42c..d0eaf98 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -44,7 +44,7 @@
 # IMPLEMENTATION, OR APPLICATIONS THEREOF, HELD BY PARTIES OTHER THAN 
 # A.M.P.A.S., WHETHER DISCLOSED OR UNDISCLOSED.
 
-cmake_minimum_required (VERSION 2.6)
+cmake_minimum_required (VERSION 3.1)
 project (AcesContainer)
 
 include (GenerateExportHeader)
@@ -66,7 +66,7 @@ if( WIN32 AND NOT CYGWIN )
   set(DEF_INSTALL_CMAKE_DIR CMake)
   set ( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W0" )
 else()
-  set(DEF_INSTALL_CMAKE_DIR lib/CMake/AcesContainer)
+  set(DEF_INSTALL_CMAKE_DIR lib/cmake/AcesContainer)
 endif()
 set(INSTALL_CMAKE_DIR ${DEF_INSTALL_CMAKE_DIR} CACHE PATH "Install directory for project CMake files" )
 
@@ -135,14 +135,7 @@ include_directories(
 # Add all targets to the build-tree export set
 export(TARGETS AcesContainer
   FILE "${PROJECT_BINARY_DIR}/AcesContainerTargets.cmake")
-# export(TARGETS AcesContainer_lib
-#  FILE "${PROJECT_BINARY_DIR}/AcesContainerTargets.cmake")
  
-# Export the package for use from the build-tree
-# (this registers the build-tree with a global CMake-registry)
-export(PACKAGE AcesContainer)
-# export(PACKAGE AcesContainer_lib)
-
 # Create the FooBarConfig.cmake and FooBarConfigVersion files
 file(RELATIVE_PATH REL_INCLUDE_DIR "${INSTALL_CMAKE_DIR}"
    "${INSTALL_INCLUDE_DIR}")
@@ -154,7 +147,7 @@ configure_file(config/AcesContainerConfig.cmake.in
   "${PROJECT_BINARY_DIR}/AcesContainerConfig.cmake" @ONLY)
 
 # ... for the install tree
-set(CONF_INCLUDE_DIRS "\${AcesContainer_CMAKE_DIR}/${REL_INCLUDE_DIR}" "\${AcesContainer_CMAKE_DIR}/${REL_INCLUDE_DIR}/aces")
+set(CONF_INCLUDE_DIRS "${INSTALL_INCLUDE_DIR}")
 set(CONF_LIB_DIRS "${INSTALL_LIB_DIR}")
 configure_file(config/AcesContainerConfig.cmake.in
   "${PROJECT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/AcesContainerConfig.cmake" @ONLY)
diff --git a/aces_attributestructs.cpp b/aces_attributestructs.cpp
index 24c02e4..9179d4e 100644
--- a/aces_attributestructs.cpp
+++ b/aces_attributestructs.cpp
@@ -228,7 +228,6 @@ acesImageContainerFlag	( 1 ),
 pixelAspectRatio	( 1.0f ),
 screenWindowWidth	( 1.0f ),
 
-
 //	initialize optional attributes to "ignored" values
 altitude			( 0.0f ),
 aperture			( 0.0f ), 
@@ -248,7 +247,6 @@ orientation			( 0 ),
 originalImageFlag	( -1 ), 
 timecodeRate		( 0 ), 
 utcOffset			( 0.0f )
-
 {	
 	//	initialize required attributes to required values
 	Chromaticities			=	ChromaticitiesForACES;
diff --git a/aces_attributestructs.h b/aces_attributestructs.h
index f28981f..e61db1c 100644
--- a/aces_attributestructs.h
+++ b/aces_attributestructs.h
@@ -305,7 +305,6 @@ struct acesHeaderInfo  {
 	timecode		timeCode;				//						TIFF tag 51043
 	string			uuid;					//						TIFF tag 42016 ImageUniqueID
 	
-	
 	//	sample custom (TIFF/EP) attributes not defined in the ACES spec
 	string			artist;					//						TIFF tag 315	artist
 	string			copyright;				//						TIFF tag 33432	copyright
diff --git a/aces_writeattributes.cpp b/aces_writeattributes.cpp
index 0e08ebd..92345b5 100755
--- a/aces_writeattributes.cpp
+++ b/aces_writeattributes.cpp
@@ -107,6 +107,31 @@
 
 #include <cassert>
 
+#define check_wrtAttr(condition, attribute, value) \
+    if (condition) wrtAttr(attribute, value)
+
+#define check_multiview(value) ((value).size() > 0)
+
+#define check_keycode(value)  ((value).filmMfcCode > 0 || \
+                               (value).filmType > 0 || \
+                               (value).prefix > 0 || \
+                               (value).count > 0 || \
+                               (value).perfOffset > 0 || \
+                               (value).perfsPerFrame > 0 || \
+                               (value).perfsPerCount > 0)
+
+#define check_timecode(value) ((value).timeAndFlags > 0 || \
+                               (value).userData > 0)
+
+#define check_v3f(value)      ((value).x != 0.0 || \
+                               (value).y != 0.0 || \
+                               (value).z != 0.0)
+
+#define check_float(value)     (value != 0.0f)
+#define check_int32(value)     (value != 0)
+#define check_string(value)   ((value).size())
+#define check_srational(value) (value.d != 0.0)
+
 using namespace std;
 
 //	=====================================================================
@@ -616,17 +641,73 @@ void aces_writeattributes:: writeHeader ( acesHeaderInfo & hi,
 	writeMagicNumberAndVersion ();
 	
 	// required aces attributes
-	wrtAttr	(	"acesImageContainerFlag",	hi.acesImageContainerFlag );
-	wrtAttr	(	"channels",					hi.channels );
-	wrtAttr	(	"chromaticities",			hi.Chromaticities );
-	wrtAttr	(	"compression",				hi.Compression );
-	wrtAttr	(	"dataWindow",				hi.dataWindow );
-	wrtAttr	(	"displayWindow",			hi.displayWindow );
-	wrtAttr	(	"lineOrder",				hi.LineOrder );
-	wrtAttr	(	"pixelAspectRatio",			hi.pixelAspectRatio );
-	wrtAttr	(	"screenWindowCenter",		hi.screenWindowCenter );
-	wrtAttr	(	"screenWindowWidth",		hi.screenWindowWidth );
-		
+	wrtAttr	(	"acesImageContainerFlag",	                hi.acesImageContainerFlag );
+	wrtAttr	(	"channels",					                hi.channels );
+	wrtAttr	(	"chromaticities",			                hi.Chromaticities );
+	wrtAttr	(	"compression",				                hi.Compression );
+	wrtAttr	(	"dataWindow",				                hi.dataWindow );
+	wrtAttr	(	"displayWindow",			                hi.displayWindow );
+	wrtAttr	(	"lineOrder",				                hi.LineOrder );
+	wrtAttr	(	"pixelAspectRatio",			                hi.pixelAspectRatio );
+	wrtAttr	(	"screenWindowCenter",		                hi.screenWindowCenter );
+	wrtAttr	(	"screenWindowWidth",		                hi.screenWindowWidth );
+
+    // aces conditional attributes
+    check_wrtAttr(check_float(hi.altitude),                 "altitude",                 hi.altitude);
+    check_wrtAttr(check_float(hi.aperture),                 "aperture",                 hi.aperture);
+    check_wrtAttr(check_string(hi.cameraFirmwareVersion),   "cameraFirmwareVersion",    hi.cameraFirmwareVersion);
+    check_wrtAttr(check_string(hi.cameraIdentifier),        "cameraIdentifier",         hi.cameraIdentifier);
+    check_wrtAttr(check_string(hi.cameraLabel),             "cameraLabel",              hi.cameraLabel);
+    check_wrtAttr(check_string(hi.cameraMake),              "cameraMake",               hi.cameraMake);
+    check_wrtAttr(check_string(hi.cameraModel),             "cameraModel",              hi.cameraModel);
+    check_wrtAttr(check_v3f(hi.cameraUpDirection),          "cameraUpDirection",        hi.cameraUpDirection);
+    check_wrtAttr(check_v3f(hi.cameraViewingDirection),     "cameraUpDirection",        hi.cameraUpDirection);
+    check_wrtAttr(check_v3f(hi.cameraPosition),             "cameraUpDirection",        hi.cameraUpDirection);
+    check_wrtAttr(check_string(hi.cameraSerialNumber),      "cameraUpDirection",        hi.cameraUpDirection);
+	check_wrtAttr(check_srational(hi.captureRate),          "captureRate",              hi.captureRate);
+	check_wrtAttr(check_float(hi.convergenceDistance),      "convergenceDistance",      hi.convergenceDistance);
+	check_wrtAttr(check_float(hi.expTime),                  "expTime",                  hi.expTime);
+	check_wrtAttr(check_float(hi.focalLength),              "focalLength",              hi.focalLength);
+    check_wrtAttr(check_float(hi.focus),                    "focus",                    hi.focus);
+    check_wrtAttr(check_srational(hi.framesPerSecond),      "framesPerSecond",          hi.framesPerSecond);
+    check_wrtAttr(check_string(hi.free),                    "free",                     hi.free);
+    check_wrtAttr(check_string(hi.headerChecksum),          "headerChecksum",           hi.headerChecksum);
+    check_wrtAttr(check_string(hi.imageChecksum),           "imageChecksum",            hi.imageChecksum);
+    check_wrtAttr(check_float(hi.imageRotation),            "imageRotation",            hi.imageRotation);
+    check_wrtAttr(check_float(hi.interocularDistance),      "interocularDistance",      hi.interocularDistance);
+    check_wrtAttr(check_float(hi.isoSpeed),                 "isoSpeed",                 hi.isoSpeed);
+    check_wrtAttr(check_float(hi.latitude),                 "latitude",                 hi.latitude);
+    check_wrtAttr(check_string(hi.lensAttributes),          "lensAttributes",           hi.lensAttributes);
+    check_wrtAttr(check_string(hi.lensMake),                "lensMake",                 hi.lensMake);
+    check_wrtAttr(check_string(hi.lensModel),               "lensModel",                hi.lensModel);
+    check_wrtAttr(check_string(hi.lensSerialNumber),        "lensSerialNumber",         hi.lensSerialNumber);
+    check_wrtAttr(check_float(hi.longitude),                "longitude",                hi.longitude);
+    check_wrtAttr(check_multiview(hi.multiView),            "multiView",                hi.multiView);
+    check_wrtAttr(check_int32(hi.originalImageFlag),        "originalImageFlag",        hi.originalImageFlag);
+    check_wrtAttr(check_string(hi.owner),                   "owner",                    hi.owner);
+    check_wrtAttr(check_string(hi.recorderFirmwareVersion), "recorderFirmwareVersion",  hi.recorderFirmwareVersion);
+    check_wrtAttr(check_string(hi.recorderMake),            "recorderMake",             hi.recorderMake);
+    check_wrtAttr(check_string(hi.recorderModel),           "recorderModel",            hi.recorderModel);
+    check_wrtAttr(check_string(hi.recorderSerialNumber),    "recorderSerialNumber",     hi.recorderSerialNumber);
+    check_wrtAttr(check_string(hi.reelName),                "reelName",                 hi.reelName);
+    check_wrtAttr(check_string(hi.storageMediaSerialNumber),"storageMediaSerialNumber", hi.storageMediaSerialNumber);
+    check_wrtAttr(check_int32(hi.timecodeRate),             "timecodeRate",             hi.timecodeRate);
+    check_wrtAttr(check_float(hi.utcOffset),                "utcOffset",                hi.utcOffset);
+    
+    // aces conditional dynamic attributes
+    check_wrtAttr(check_string(hi.capDate),                 "capDate",                 hi.capDate);
+    check_wrtAttr(check_int32(hi.imageCounter),             "imageCounter",            hi.imageCounter);
+    check_wrtAttr(check_keycode(hi.keyCode),                "keyCode",                 hi.keyCode);
+    check_wrtAttr(check_timecode(hi.timeCode),              "timeCode",                hi.timeCode);
+    check_wrtAttr(check_string(hi.uuid),                    "lensAttributes",          hi.lensAttributes);
+    
+    // aces conditional custom (TIFF/EP) attributes
+    check_wrtAttr(check_string(hi.artist),                  "artist",                  hi.artist);
+    check_wrtAttr(check_string(hi.copyright),               "copyright",               hi.copyright);
+    check_wrtAttr(check_string(hi.dateTime),                "dateTime",                hi.dateTime);
+    check_wrtAttr(check_int32(hi.orientation),              "orientation",             hi.orientation);
+    check_wrtAttr(check_string(hi.software),                "software",                hi.software);
+    
 	// terminator
 	writeChar ( 0 );