What effect does increasing the source-to-object distance have on magnification in paralleling?

• A. Increases Magnification
• B. No Effect on Magnification
• C. Variable with Receptor Angle
• D. Decreases Magnification

Answer: (D)

Magnification in radiography is driven by the ratio SID/SOD. Increasing the distance from the X-ray source to the object lowers this ratio, so the image size on the receptor becomes closer to the true object size and magnification decreases. In other words, the farther the object is from the source, the less magnified the image will be (while keeping the receptor setup aligned). If, instead, you increased the object-to-receptor distance, magnification would increase. Thus, increasing the source-to-object distance reduces magnification.