diff --git a/examples/open_pbr_default.mtlx b/examples/open_pbr_default.mtlx
index 756eda8a..8125541a 100644
--- a/examples/open_pbr_default.mtlx
+++ b/examples/open_pbr_default.mtlx
@@ -37,7 +37,7 @@
     <input name="coat_darkening" type="float" value="1.0" />
     <input name="thin_film_weight" type="float" value="0" />
     <input name="thin_film_thickness" type="float" value="0.5" />
-    <input name="thin_film_ior" type="float" value="1.5" />
+    <input name="thin_film_ior" type="float" value="1.4" />
     <input name="emission_luminance" type="float" value="0.0" />
     <input name="emission_color" type="color3" value="1, 1, 1" />
     <input name="geometry_opacity" type="float" value="1" />
diff --git a/index.html b/index.html
index 04426758..8b6347c9 100644
--- a/index.html
+++ b/index.html
@@ -868,7 +868,7 @@
 --------------------------|-----------|----------|:---------------:|:-------------:|:--------:|----------------------------------------------
 **`thin_film_weight`**    | Weight    | `float`  | $ [0, 1]      $ |               | $ 0    $ | Coverage weight of the thin film
 **`thin_film_thickness`** | Thickness | `float`  | $ [0, \infty) $ | $ [0, 1]    $ | $ 0.5  $ | Thickness of the film in micrometers ($\mathrm{\mu m}$)
-**`thin_film_ior`**       | IOR       | `float`  | $ (0, \infty) $ | $ [1, 3]    $ | $ 1.5  $ | Refractive index of the film
+**`thin_film_ior`**       | IOR       | `float`  | $ (0, \infty) $ | $ [1, 3]    $ | $ 1.4  $ | Refractive index of the film
 
 ![](images/thin_film_0nm.png width=99%) ![](images/thin_film_300nm.png width=99%) ![](images/thin_film_600nm.png width=99%)
 <div class="shifted-caption">
diff --git a/parametrization.md.html b/parametrization.md.html
index eb37cb0e..d87d1581 100644
--- a/parametrization.md.html
+++ b/parametrization.md.html
@@ -63,7 +63,7 @@
 | **Thin-film**                                                                                                                                         |
 | `thin_film_weight`                    | Weight              | `float`   | $ [0, 1]        $ |               | $ 0                $ |                  |
 | `thin_film_thickness`                 | Thickness           | `float`   | $ [0, \infty)   $ | $ [0, 1] $    | $ 0.5              $ | $\mathrm{\mu m}$ |
-| `thin_film_ior`                       | IOR                 | `float`   | $ (0, \infty)   $ | $ [1, 3]    $ | $ 1.5              $ |                  |
+| `thin_film_ior`                       | IOR                 | `float`   | $ (0, \infty)   $ | $ [1, 3]    $ | $ 1.4              $ |                  |
 | **Geometry**                                                                                                                                          |
 | `geometry_opacity`                    | Opacity             | `float`   | $ [0, 1]        $ |               | $ 1                $ |                  |
 | `geometry_thin_walled`                | Thin walled         | `boolean` | {false, true}     |               | false                |                  |
diff --git a/reference/open_pbr_surface.mtlx b/reference/open_pbr_surface.mtlx
index d57a18a6..b74bae00 100644
--- a/reference/open_pbr_surface.mtlx
+++ b/reference/open_pbr_surface.mtlx
@@ -69,7 +69,7 @@
            doc="Coverage weight of the thin-film. Use for materials such as multi-tone car paint or soap bubbles." />
     <input name="thin_film_thickness" type="float" value="0.5" uimin="0.0" uisoftmax="1.0" uiname="Thin Film Thickness" uifolder="Thin Film" uiadvanced="true"
            doc="The thickness of the thin-film layer on the base (in micrometers)." />
-    <input name="thin_film_ior" type="float" value="1.5" uimin="0.0" uisoftmin="1.0" uisoftmax="3.0" uiname="Thin Film Index of Refraction" uifolder="Thin Film" uiadvanced="true"
+    <input name="thin_film_ior" type="float" value="1.4" uimin="0.0" uisoftmin="1.0" uisoftmax="3.0" uiname="Thin Film Index of Refraction" uifolder="Thin Film" uiadvanced="true"
            doc="The index of refraction of the thin-film." />
     <input name="emission_luminance" type="float" value="0.0" uimin="0.0" uisoftmax="1000.0" uiname="Emission Luminance" uifolder="Emission"
            doc="The amount of emitted light, as a luminance in nits." />