What happens when the beam is not properly centered on a grid?

When the beam is not properly centered on a grid, one of the primary consequences is the phenomenon known as "grid cutoff." This occurs because grids are designed to absorb scatter radiation while allowing primary radiation to pass through. If the x-ray beam is misaligned or not centered on the grid, some of the primary beam can be absorbed by the grid instead of reaching the film or detector, leading to a reduction in exposure in specific areas. This can result in areas of the image appearing overexposed or very light, while other areas may remain properly exposed, creating a significant contrast that can degrade overall image quality.

The other outcomes listed are not associated with improper beam alignment on a grid. Increased film clarity is generally a result of optimal dose and alignment, while uniform exposure requires proper centering to achieve even distribution of the beam across the entire field. Decreased radiation dose is not applicable here, as improper centering often leads to increased necessary exposure to compensate for loss of information in areas due to the cutoff.