Which object-to-image distance (OID) would result in the greatest amount of penumbra?

The amount of penumbra, which refers to the blurry or indistinct area around the edges of a radiographic image, increases with a greater object-to-image distance (OID). This phenomenon occurs due to the geometric properties of the X-ray beam.

When the OID is larger, the rays that diverge from the object being imaged must travel a greater distance before they reach the image receptor. This divergence causes less precise edge definition, resulting in a softer shadow and increased penumbra. In contrast, a smaller OID allows the X-ray beams to be more collimated, leading to sharper edges on the image and reduced penumbra.

Therefore, with a 2.0 inches OID, the penumbra is more pronounced than at smaller distances, and at a 3.0 inches OID, it becomes even more substantial. This large distance further enhances the effect, producing the greatest amount of penumbra compared to other options provided.