diff --git a/app/views/publications/_viewer.html.erb b/app/views/publications/_viewer.html.erb
index f4f31d3..f000224 100644
--- a/app/views/publications/_viewer.html.erb
+++ b/app/views/publications/_viewer.html.erb
@@ -847,7 +847,7 @@
         enableXfa: ENABLE_XFA,
         disableFontFace: true
     });
-    var pdfDoc = null, scale = 2.5;
+    var pdfDoc = null, scale = window.devicePixelRatio || 1;
     const container = flipbook[0];
     flipbook.bind('zoom-min', function(){
         flipbook_container.find('.cmdZoomOut').addClass('disabled');
@@ -889,6 +889,7 @@
         var viewport = page.getViewport({ scale: scale });
         // Support HiDPI-screens.
         var outputScale = (window.devicePixelRatio || 1) / 4;
+        outputScale = outputScale / viewport.width * flipbook.width();
         canvas.width = Math.floor(viewport.width * outputScale);
         canvas.height = Math.floor(viewport.height * outputScale);
         canvas.style.width = "100%";
@@ -1082,7 +1083,7 @@
                 var viewport = page.getViewport({ scale: scale });
                 // Support HiDPI-screens.
                 var outputScale = window.devicePixelRatio || 1;
-
+                outputScale = outputScale / viewport.width * flipbook.width();
                 canvas.width = Math.floor(viewport.width * outputScale);
                 canvas.height = Math.floor(viewport.height * outputScale);
                 canvas.style.width = "100%";