In this video, I discuss the new IOR Index parameter in the Specular section of the new Principled BSDF in Blender 4.0. I also show the updated Specular Tint parameter. #blendertutorial #iorindex #indexofrefraction #blender4 #speculartint Here is the material tester file used in this tutorial which I developed for testing purposes. https://drive.google.com/file/d/1Jor8jrtZAaomN5EsxKAaLS_Pyyr9EjfE/view?usp=sharing 00:00 Introduction 00:39 Two ways to set specular 02:45 Some theory behind index of refraction 03:08 Specular highlight 03:50 The fresnel curve 05:20 About refraction, how it relates to reflections 10:00 Specularity and backward compatibility with 3.6 files 12:18 IOR Level linearizes low end reflection control 15:28 Examples of using IOR Level 13:33 Turning off specular reflections, diffuse only 19:12 Using Specular Tint