Via canonrumors
https://www.lensrentals.com/blog/2017/05/yet-another-post-about-my-issues-with-uv-filters/ (https://www.lensrentals.com/blog/2017/05/yet-another-post-about-my-issues-with-uv-filters/)
et
https://www.lensrentals.com/blog/2016/12/front-element-lens-protection-revisited/ (https://www.lensrentals.com/blog/2016/12/front-element-lens-protection-revisited/)