Okay, you've got your dialogue scene all set up and you're about to shoot an over-the-shoulder shot. Perfect! Classic! But damn it, if the actor whose shoulder you're shooting over even moves a couple inches forward, your other actor's face will be totally blocked from the camera. Perfect! Classic! Since asking your actors to sit completely still would result in some weirdly robotic performances, you can always shoot the scene handheld in order to adjust your camera placement with the movements of your actors, but if you're not keen on that, you can try a method Rubidium Wu of Crimson Engine describes in his latest video.
Sliders are great, versatile tools that can do way more than give you a nice, smooth lateral movement for b-roll shots. As Wu points out in the video, sliders give you a way to adjust your camera placement without 1.) being forced to go handheld, and 2.) having to shoulder the weight of your camera rig.
It's not the most revolutionary technique for capturing over-the-shoulder shots, but it does work and it's not a very obvious choice for many new filmmakers. So, the next time you're shooting a scene with dialogue, consider busting out your slider. It'll not only free up your back and arms but it will free up your actors to give a more natural performance.
Source: Crimson Engine