This modification of the CMF phone 2 pro cover has a built-in slider that can be used to adjust the flash light of the phone. The color of the filament for the slider determines the light. With white filament, the flash light should be somewhat more diffuse, which can contribute to more beautiful pictures.

Unfortunately I don't have a CMF phone, so I couldn't test the function on the smartphone, but The slider works but might need some slides to be moving more smooth.