Smash cut to add suspense.
Sci-fi movies, thrillers, and horror films often cut from the middle of a scene at the moment of greatest tension to start a new scene. “They change the vibe. A scene looks like it’s going in one direction, but the smash cut goes to something completely different,” says Cann.
Smash cut to avoid.
A smash cut can go straight from a murder about to happen to the police detective at the murder scene, standing over the dead body. Or, if the characters in your love story are about to have twins, you can smash cut to a close-up of the kids years later, once they're old enough to have adventures of their own. If the actor just can’t perform a convincing combination of emotions that you need, you can try screenwriting around it. Smash cut to a later moment when the character has had a chance to process events.
A smash cut can help you use your audience’s emotions to amplify the scene. Sometimes a viewer’s imagination can conjure up something more terrifying or beautiful or fantastic than you can possibly put on film. Avoid expensive special effects that may come off as cheesy, and leave the gruesome violence, awesome spaceship, or godlike presence to the viewer’s imagination with a smash cut at a crucial moment.