try this one.

_layouts/gallery_page.html

@@ -36,8 +36,7 @@
         width="{{ image[1] | divided_by: site.gallery.thumbnail_size.retina }}"
         height="{{ site.gallery.thumbnail_size.y | divided_by: site.gallery.thumbnail_size.retina }}" />
     </a>
-    {% assign image_root = "/usr/local/jekyll/sites/photos.kameronkenny.com/_site/photos/san_francisco/" %}
+    {% assign image_path = "{page.path.split('/index.html')[0]}/#{image[0]}" %}
-    {% assign image_path = image_root.concat(image[0]) %}
     {% capture has_exif %}{{ image_path | exif: "exif?" }}{% endcapture %}
     {% if has_exif %}
       Camera: {{ image_path | exif: 'model' }}