The contrast rendering factor CRF is used to label reflected glare on horizontal, glossy surfaces (q.v. chapter 1.2 section "Reflected glare on horizontal visual tasks"). Measurements can be executed using a specialised measuring instrument or image resolution devices. The measuring field corresponds to the particular position and the usual viewing direction of the observer relating to that surface.
CRF measurement
![](https://www.trilux.com/en/lighting-practice/fileadmin/user_upload/Abb_CRF_en.pdf.png)
Figure 3.76: Viewing angle and reference field for CRF measurement