Eli5: Why is it that when wide FOV is displayed on camera, it’s distorted?

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Why is the “peripheral vision” of wide field of vision footage curved but irl peripheral vision is normal?

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Anonymous 0 Comments

Whenever the screen you are viewing does not cover the same amount of your visual field as its FoV then it will be distorted. The human visual field is around 120 degrees so to properly view that on a screen it would need to be everything you can see.

The peripheral vision is “curved” as you say because it is the edge of a hemisphere squashed onto a smaller flat plane. Conceptually 360 degree vision would be a sphere, right? So if you flatten 180 degrees onto a flat surface you get the same kind of distortion you would get turning a globe into a flat map.

Anonymous 0 Comments

> but irl peripheral vision is normal

Let’s say it *seems* normal. We only get very blurry visual cues from peripheral vision and our brain has learned to organize them into “normal” perceptions. (Color vision decreases there too, yet we don’t notice that either.)

That the retina is curved helps too.

> Why is the “peripheral vision” of wide field of vision footage curved

Cameras have two imperatives: 1) *everything* has to be reasonably sharp (not only in the center, as for our eyes); 2) the receptor, film or digital sensor, has to be *flat*.

If you’re OK with mediocre sharpness and a very small aperture, a pinhole camera will give you perfectly straight lines (called *orthoscopy*) over a very wide filed of view as in this [example](https://i.imgur.com/1LTqzzF.jpeg). (Some people call the effect “perspective distorsion”, but that’s a misnomer.)

But if you need sharpness and more light-gathering, you need an objective. Expecting it to be sharp, orthoscopic, with a flat image field and with a great aperture is a daunting task – and heavy on the customer’s wallet. So compromises are made and chosen by the designer, one of them being giving up on orthoscopy. Sometimes it’s just a bit of barrel distorsion in cheap point-and-shoot cameras, sometimes it’s a full “fish-eye” rendition to get extreme fields of view as in this [example](https://i.imgur.com/sp89BEo.jpeg).