diff --git a/gray-card.md b/gray-card.md
index 8777094b7..5cc802ea9 100644
--- a/gray-card.md
+++ b/gray-card.md
@@ -2,9 +2,11 @@
 
 - [[pull]] [[grey card]]
 - [[go]] https://en.wikipedia.org/wiki/Gray_card
+  - [[quote]] A primary use of gray cards is to provide a [[standard reference object]] for exposure determination in photography. A gray card is an (approximate) realization of a [[Lambertian]] scatterer; its apparent brightness (and exposure determination) therefore depends only on its orientation relative to the light source. 
 
 
 [//begin]: # "Autogenerated link references for markdown compatibility"
 [pull]: pull "Pull"
 [go]: go "Go"
+[quote]: quote "Quote"
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diff --git a/lambertian.md b/lambertian.md
new file mode 100644
index 000000000..6660c39cb
--- /dev/null
+++ b/lambertian.md
@@ -0,0 +1,10 @@
+# Lambertian
+
+- [[go]] https://en.wikipedia.org/wiki/Lambertian_reflectance
+  - [[quote]] Lambertian reflectance is the property that defines an [[ideal]] "[[matte]]" or diffusely reflecting surface. 
+
+
+[//begin]: # "Autogenerated link references for markdown compatibility"
+[go]: go "Go"
+[quote]: quote "Quote"
+[//end]: # "Autogenerated link references"
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