diff --git a/topics/01_cameras/index.md b/topics/01_cameras/index.md
index 14ead8c381a4552a31b0f6adc4b6db5b9447df69..9f43a33a2b8b7aec2cad2a09fe0ad58863d283d5 100644
--- a/topics/01_cameras/index.md
+++ b/topics/01_cameras/index.md
@@ -135,6 +135,8 @@ It is common to choose the $z$ axis to point **toward** the scene, and the $y$ a
 
 We'll focus on the two main families of digital sensors: CCD and CMOS. In both families, the actual light sensing is based on the electron-hole pair generation in MOS photodiodes. The main difference is how this charge is converted to a signal, offering tradeoffs over complexity, signal-to-noise ratio and readout speed.
 
+The **ISO** of a sensor is a metric characterizing its sensitivity to light. The same metric is used for both analog and digital sensors. The ISO of a film is a function of its chemistry, while the ISO of a digital sensor is a function of its digital gain. Standard ISO values follow a logarithmic scale: 100, 200, 400, 800, 1600, 3200, etc.
+
 ### CCD
 
 ![](img/ccd.png)