What is distortion?

Linear perspective tutorials like drawabox often mention distortion, but never define it. Wikipedia defines distortion for photography and optics and they seem related, but I want a definition specifically for drawing.

• Hi d_iv, can you cite a few references? What distortion exactly are you talking about? The visual distortion in the links you give can be applied to perspective construction, but why do you want a definition, specifically?
– Joachim
Commented Feb 9, 2022 at 6:19
• Added a link to a relevant tutorial. I want a definition because supposedly distortion is bad. Without knowing the definition I can't identify it, and if I can't identify it, I can't correct it.
– d_iv
Commented Feb 9, 2022 at 17:06
• Do you have any reason to believe there's a special definition separate from the dictionary definition? dictionary.com/browse/distort Commented Feb 9, 2022 at 17:42
• I agree with Allison C. It seems like if the author meant something different from the common definition, they would have been more explicit in defining and explaining it. When the term is used in different specialties, the meaning doesn't change, just how it commonly manifests in that application or medium. Commented Feb 9, 2022 at 19:00
• I think the word "distortion" is misleading and incorrect. In the article you linked, it's a limitation of a system we have invented to recreate apparent visual depth/volume. It's neither a distortion within that system nor of what it represents (if this is something you'd consider an answer, I can elaborate this comment as an answer).
– Joachim
Commented Feb 9, 2022 at 22:05

The distortion discussed in the Drawbox article are related to using a two point perspective in a manner that makes the object in the drawing look distorted.

Wikipedia has a nice article on the limitations of the two point perspective.

Perspective images are calculated assuming a particular vanishing point. In order for the resulting image to appear identical to the original scene, a viewer of the perspective must view the image from the exact vantage point used in the calculations relative to the image. This cancels out what would appear to be distortions in the image when viewed from a different point. These apparent distortions are more pronounced away from the center of the image as the angle between a projected ray (from the scene to the eye) becomes more acute relative to the picture plane.

The wiki article has this picture to illustrate misusing

The work shows a scene that provides many deliberate examples of confused and misplaced perspective effects. Although the individual components of the scene seem self-consistent, the scene itself can be classed as an example of an impossible object.

Partial list of "errors"

1. The man in the foreground's fishing rod's line passes behind that of the man behind him.
2. The sign is moored to two buildings, one in front of the other, with beams that show no difference in depth
3. The sign is overlapped by two distant trees.

The wiki article goes on to list many more errors in the picture - these are all examples of distortion