You know those shots where a camera is pointing at an out of focus object and then it slowly goes into focus. Sometimes this is done by focus racking (or focus pulling) but sometimes it’s done by actually moving the camera until the object gets inside the depth of field.
The secret to doing it right with camera movement is to get the movement really (REALLY!) smooth. You can probably do it with a table dolly, but to get a really smooth movement you need to use something with bearings. Luckily, there is another industry that uses sliders with bearings – the furniture industry.
Photographer Romero Dominguez shares a pretty nice hack on how to build a slider with a couple of drawers sliding guide rails and a few scraps of metal. Depending on your needed length, those starts as little as $15.