The images shown represent keystone distortion, which occurs when a projector is not aligned perpendicularly to the screen. This misalignment results in a trapezoidal image rather than a rectangular one.
According to the AVIXA CTS Exam Guide, keystone distortion is covered under the Display Systems section, which states:
“Keystone distortion happens when the projector lens is not perpendicular to the screen plane, often due to improper vertical or horizontal positioning. The image appears wider at one end and narrower at the opposite, forming a shape like a keystone — hence the name.”
This distortion is not related to contrast (A), which refers to the difference between light and dark elements in an image, nor chromatic (B), which pertains to color distortion or aberration. While the shapes resemble trapezoids, trapezoid (D) is a description of the resulting shape, not the distortion type. The technical term for this specific distortion is keystone.
[Reference:, AVIXA CTS Exam Guide, 5th Edition – Chapter 7: Display Systems, page 145-147., CTS-D Body of Knowledge: Image Display and Projection Techniques, Keystone Correction section., , , , ]
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