What is an immediate effect of a low-quality cut on a diamond?

A low-quality cut significantly impacts a diamond's ability to reflect and refract light, which is crucial for its overall brilliance and sparkle. When a diamond is cut poorly, it does not interact with light in the optimal way, resulting in reduced light performance. This means that light entering the diamond does not return to the viewer's eye effectively, leading to a less vibrant appearance. In contrast, a well-cut diamond maximizes light performance, enhancing its beauty through brightness and scintillation.

As a result, the immediate effect of a low-quality cut is evident in its diminished light performance, making this the correct answer. The alternative choices focus on aspects of clarity, color, and perceived size that are not directly influenced by the quality of the cut in the same manner as light performance is impacted.