Contrast threshold IMX 636

Contrast threshold IMX 636

Hello, 

I've been watching this video (Metavision Training Videos | Introduction to Event-Based Vision Sensor) to understand the definition of contrast threshold. They mentioned that IMX 636 sensor uses a log definition of contrast but I haven't found any documentation about this. I would like to understand a little bit more, can you please write down the log equation and explain what is the difference with the temporal contrast?

Thank you.