Why does a lens automatically produce perspective?

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    Lens Perspective
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Discussion Overview

The discussion revolves around the concept of perspective as it relates to lenses and cameras, exploring how these devices reproduce three-dimensional scenes onto a two-dimensional plane. Participants examine whether this phenomenon can be explained through ray tracing and delve into the implications of depth perspective and geometric distortions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question what is meant by "creates perspective," suggesting it may be an intrinsic result of how lenses focus light.
  • Others argue that perspective is inherent in the scene itself, while lenses merely focus and record light patterns from that scene.
  • A participant explains that depth perspective arises from varying magnification with object distance, proposing a ray tracing approach to visualize this effect.
  • Another participant discusses the concept of foreshortening and how distance, point of view, and focal length contribute to geometric distortions in images, noting that cameras automatically introduce these perspective artifacts.
  • Telecentric lenses are mentioned as an exception, as they do not create perspective distortions, with an example involving a cylinder along the optical axis illustrating this point.
  • A comparison is drawn between the techniques used by artists to depict perspective and the effects produced by lenses and optics, raising questions about the similarities between the two processes.

Areas of Agreement / Disagreement

Participants express differing views on the nature of perspective in relation to lenses, with no consensus reached on whether lenses create perspective or merely reproduce it from the scene. The discussion remains unresolved regarding the precise mechanisms at play.

Contextual Notes

Some assumptions about the definitions of perspective and the role of lenses may be missing, and the discussion does not fully resolve the mathematical or conceptual intricacies involved in ray tracing or the effects of different lens types.

fisico30
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Hello Forum,

can anyone explain why a camera, a lens, automatically creates perspective in an image?
Is it explainable with ray tracing?

thanks
fisico30
 
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What do you mean by "creates perspective"?
Edit: I guess you could say it's simply an intrinsic result of focusing light.
 
I don't know what you mean by the lens creating perspective. The perspective is in the scene, the lens focuses the light from the scene, the camera records the light patterns.
 
fisico30 said:
Hello Forum,

can anyone explain why a camera, a lens, automatically creates perspective in an image?
Is it explainable with ray tracing?

thanks
fisico30

If you are referring to 'depth perspective', the answer is that magnification varies with object distance. In terms of ray tracing, put two objects of equal size at the front-and-rear edges of the depth of focus and see what the image heights are.
 
Hello everyone,

so reality is 3D and lenses, cameras, are trying to reproduce that 3D reality on a 2D plane...

I have recently read about foreshortening in perspective. Depending on the distance, point of view and focal length of the lens, we can get certain geometric distorsions in the picture; parallel lines seem to go to the vanishing point and the farther the object the smaller it is...
Automatically, a camera introduces all these artifacts of perspective (sometimes they are exaggerated too). In wikipedia, perspective has two attributes:
Objects appear smaller as their distance from the observer increases;
Foreshortened: the size of an object's dimensions along the line of sight are relatively shorter than dimensions across the line of sight;

Telecentric lenses, which I mentioned some time ago, don't create perspective distorsions...
for example a cylinder that lies along the optical axis seems to converge to the vanishing point. The rear of the cylinder appears smaller and the body of the cylinder appears oblique since parallel lines seem to converge to the vanishing point...

fisico30
 
An artist, when drawing a scenary, uses the laws of perspective to recreate the same effect that we have when we look at the real 3D world...

It seems that lenses and optics somehow do the same...is that true?
 

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