Music, there's a very cool feature in the D 850 called autofocus fine-tune. It allows you to optimize your lenses while in the field, and it's really simple to do from the back of the camera. Just press the menu button and navigate to the setup menu. In the setup menu, choose autofocus fine-tune and turn on the feature. To actually fine-tune, hold the autofocus button and the movie record button on the outside of the camera. While in Live View, press both of those buttons together and follow the prompts on the camera. Once you've optimized your lenses, the camera will store the value for each lens for future use.