Final answer:
The opening shot from darkness in an expanding circle of light, often found in silent films, is called an Iris shot. This cinematographic technique focuses attention and gracefully transitions in or out of a scene.
Step-by-step explanation:
The shot described in the question is known as an Iris shot. This technique was commonly used in the era of silent films. An Iris shot features an expanding circle that transitions from darkness to light, revealing the scene. It is similar to the opening of an eye, which is where the name 'iris' comes from. The Iris shot was often utilized to focus the viewer's attention to a particular part of the scene or to transition in or out of a scene gracefully.