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Piranesi's Perspective Trick (2019)

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Re: Piranesi's Perspective Trick (2019)

#81

Post by kqr »

WantonQuantum wrote: post #75
Etherlord87 wrote: post #62

Earlier quoted context omitted.

You make good points, but if we really perceived reality differently than cameras, someone would write an article about that - after all you can take a photo on your smartphone and compare to your IRL view. Yes it's hard to make it match but it's possible. Since no one made an experiment to show this, and since we understand pretty well the optics of a human eye, I think the cameras actually reproduce human vision de…

One thing that cameras can do that we can't do with our (unaided) eyes is change focal length. When a camera zooms in or zooms out, there is a change in the geometry of perspective. When zooming in, the change is difficult to see but is well documented. Portrait photographers are well aware of this because it tends to make people look better. When zooming out, especially when zooming out to a very wide field of view,…

> When a camera zooms in or zooms out, there is a change in the geometry of perspective.

This is the opposite of what happens. The perspective is exactly the same, only cropped to a narrower field of view.

Changed perspective would be counteracting the lens zoom with foot zoom -- now this causes the change in perspective you talk about. But it's caused entirely by moving the camera. The zoom is just to preserve framing and could just as well be accomplished by cropping in post, assuming sufficient resolution.

Re: Piranesi's Perspective Trick (2019)

#82

Post by nyanpasu64 »

kqr wrote: post #81
WantonQuantum wrote: post #75

Earlier quoted context omitted.

One thing that cameras can do that we can't do with our (unaided) eyes is change focal length. When a camera zooms in or zooms out, there is a change in the geometry of perspective. When zooming in, the change is difficult to see but is well documented. Portrait photographers are well aware of this because it tends to make people look better. When zooming out, especially when zooming out to a very wide field of view,…

> When a camera zooms in or zooms out, there is a change in the geometry of perspective. This is the opposite of what happens. The perspective is exactly the same, only cropped to a narrower field of view. Changed perspective would be counteracting the lens zoom with foot zoom -- now this causes the change in perspective you talk about. But it's caused entirely by moving the camera. The zoom is just to preserve frami…

I think foot zoom is the primary reason for faces looking weird (big noses) in smartphone selfies, while "a photograph occupying less of your FOV than the camera was capturing" is why people at the edge of a photo look distorted.

Re: Piranesi's Perspective Trick (2019)

#83

Post by RheingoldRiver »

account42 wrote: post #79
RheingoldRiver wrote: post #70

Earlier quoted context omitted.

if you have any connection to the admins of that wiki, it would be great to get MultimediaViewer extension enabled - https://www.mediawiki.org/wiki/Extension:MultimediaViewer they're on 1.35 right now which is a bit out of date (lifecycle - https://www.mediawiki.org/wiki/Version_lifecycle ) but an older branch of MMV should work fine on 1.35

I hate this behavior on Wikipedia. Worst part is that people then share links to those views which don't work without running javashit.

If you have an account, you can disable it in preferences. Appearance -> Files -> "Enable Media Viewer" Toggle that off and it'll never happen again

Re: Piranesi's Perspective Trick (2019)

#85

Post by kazinator »

This reminds me of an issue in vintage computer graphics. Say you have a game with some polygons happening, and they're nicely rendered in 3D perspective. You'd like to add some snazzy textures to them.

Here's a problem. The textures have to be put through a perspective projection. As in every pixel.

It's possible to cheat. You can simply use a bicubic stretch or even linear. It really shows up when the polygons are large and they rotate to create deep perspective. You see an artifact whereby the center of the texture does not stay centered on the polygon as it rotates.

Re: Piranesi's Perspective Trick (2019)

#86

Post by WantonQuantum »

kqr wrote: post #81
WantonQuantum wrote: post #75

Earlier quoted context omitted.

One thing that cameras can do that we can't do with our (unaided) eyes is change focal length. When a camera zooms in or zooms out, there is a change in the geometry of perspective. When zooming in, the change is difficult to see but is well documented. Portrait photographers are well aware of this because it tends to make people look better. When zooming out, especially when zooming out to a very wide field of view,…

> When a camera zooms in or zooms out, there is a change in the geometry of perspective. This is the opposite of what happens. The perspective is exactly the same, only cropped to a narrower field of view. Changed perspective would be counteracting the lens zoom with foot zoom -- now this causes the change in perspective you talk about. But it's caused entirely by moving the camera. The zoom is just to preserve frami…

You are 100% correct! I was unconsciously assuming the foot zooming. Thanks for picking that up!

Re: Piranesi's Perspective Trick (2019)

#87

Post by animatethrow »

kazinator wrote: post #85

This reminds me of an issue in vintage computer graphics. Say you have a game with some polygons happening, and they're nicely rendered in 3D perspective. You'd like to add some snazzy textures to them. Here's a problem. The textures have to be put through a perspective projection. As in every pixel. It's possible to cheat. You can simply use a bicubic stretch or even linear. It really shows up when the polygons are…

Playstation 1 didn't do perspective correct texture mapping. If you scroll way down this WebGL tutorial page a few examples are shown:

https://webglfundamentals.org/webgl/lessons/webgl-3d-perspec...

Re: Piranesi's Perspective Trick (2019)

#88

Post by bazoom42 »

Etherlord87 wrote: post #62
SamBam wrote: post #10

> By legibility I mean that the Piranesi distortion is easier to read, and that to anyone unfamiliar with photographs, that hasn’t grown up with TV, photographs and magazines, the Piranesi version would look much better, and the true perspective would look rather odd. I think this is a key point that people are often unaware of. For instance, whenever I see a modern artist who has painted photorealistic art, I read d…

You make good points, but if we really perceived reality differently than cameras, someone would write an article about that - after all you can take a photo on your smartphone and compare to your IRL view. Yes it's hard to make it match but it's possible. Since no one made an experiment to show this, and since we understand pretty well the optics of a human eye, I think the cameras actually reproduce human vision de…

Just one well known difference: Human have two eyes and we use the difference to determine distances. A photo is flat.

Another difference: In human sigth you can only focus on the center of the vision field, while on a photograph you can look at unfocused points and observe the distortion on the edges of the picture. Human observation (like looking at the bridge in the pic) is really a series of observations where we move the focus.

Re: Piranesi's Perspective Trick (2019)

#90

Post by bazoom42 »

SamBam wrote: post #10

> By legibility I mean that the Piranesi distortion is easier to read, and that to anyone unfamiliar with photographs, that hasn’t grown up with TV, photographs and magazines, the Piranesi version would look much better, and the true perspective would look rather odd. I think this is a key point that people are often unaware of. For instance, whenever I see a modern artist who has painted photorealistic art, I read d…

Notably, photorealism is called photorealism because it deliberatley tries to reproduce photography, not because it tries to reproduce observable reality.
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