An increase in object-to-image distance (OID) will lead to which two effects?

An increase in object-to-image distance (OID) primarily results in decreased spatial resolution. This occurs because as the distance between the object and the image receptor increases, the image detail becomes less sharp due to the divergence of the x-ray beam. The more the x-rays spread out, the more the distinct edges of the object blur, ultimately leading to a lower quality image with less clarity.

Additionally, an increase in OID also leads to increased penumbra. The penumbra is the zone around the edges of a radiographic image where the image transitions from black to white; it represents the blurring that occurs at the edges of the object being imaged. As OID increases, the edges of the object produce a larger penumbra, further contributing to a loss of image sharpness.

In summary, increased OID results in decreased spatial resolution and increased penumbra, reflecting the inherent trade-off between distance and image quality in radiographic imaging.