What happens when an object is behind the focal trough?

• A. Image appears narrower
• B. Image appears wider mesially-distally
• C. No distortion
• D. Image appears upright

Answer: (B)

In panoramic imaging, the focal trough is the zone where structures are imaged sharply. Objects that lie outside this zone are projected with magnification and blur because the divergent beam and curved geometry pull their image away from the ideal focal plane. When something sits behind the focal trough, its projection is stretched along the arch, so it appears wider in the mesiodistal (width) direction. It won’t look narrower, perfectly distortion-free, or upright—the off-trough position primarily causes horizontal magnification and blur.