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-   -   maybe I don't know the right terms for a fisheye shape (https://www.mersenneforum.org/showthread.php?t=24560)

 jasong 2019-07-02 00:28

maybe I don't know the right terms for a fisheye shape

[url]https://www.bing.com/images/search?q=fisheye+view+grid&FORM=HDRSC2[/url]

I'm watching a lot of first amendment audit videos(US videos, free speech amendment) and sometimes people are accused of standing too close, which can be hard to determine with a fisheye video.

I'm looking for a picture that basically shows me mathematically, how far away stuff is. Optimally, I'd like to have a fisheye shape I could just put over a Youtube video, but I know that's a rainbows and unicorns type dream.

Have a nice day. :)

 Dr Sardonicus 2019-07-02 13:34

[QUOTE=jasong;520501]I'm looking for a picture that basically shows me mathematically, how far away stuff is.[/QUOTE]
No can do. A camera renders a 3-D subject into a 2-D perspective image. This allows all sorts of mischief. As an example, I suggest you look up the [url=http://psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/ames_room.html]Ames room[/url].

 jasong 2019-07-02 13:49

[QUOTE=Dr Sardonicus;520538]No can do. A camera renders a 3-D subject into a 2-D perspective image. This allows all sorts of mischief. As an example, I suggest you look up the [url=http://psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/ames_room.html]Ames room[/url].[/QUOTE]
Are you claiming different cameras can fisheye differently?

The way I see it, and maybe I'm wrong, but if a camera says it does, say, 170 degrees, and it's a 16:9 image, I would think someone with the proper knowledge and software could simulate that. I don't have the knowledge for that,so I'm playing the role of a beggar. :)

It's not a huge deal for me, maybe it's harder than I think.

Tbh, I was hoping I was simply using the wrong Google terms. I've seen some of the images on Google, and I'm simply looking for one where the point of view is at the center of the ellipse(?) going out.

 Uncwilly 2019-07-02 13:55

Different cameras have different 'fisheye' lenses. The distortions are different. The angle covered by the lens is not a guarantee of the same representation on the image. Some lenses are more akin to a true panoramic, while others have a high drop-off on the sides. Also, they don't have to have the same rotational symmetry (up-down vs left-right can be different curves). Further, the sensor or film can be shaped to change the effect.

 jasong 2019-07-02 13:57

[QUOTE=Dr Sardonicus;520538]No can do. A camera renders a 3-D subject into a 2-D perspective image. This allows all sorts of mischief. As an example, I suggest you look up the [url=http://psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/ames_room.html]Ames room[/url].[/QUOTE]
I'm certainly not an expert, but if you think about it, everything you see is a 2-d image, a spherical image that impinges on your eyeball.

I think most of the distortion would be going from a spherical image to a flat screen, so even regular tv is distorted.

 Dr Sardonicus 2019-07-02 14:44

[QUOTE=jasong;520541]Are you claiming different cameras can fisheye differently
<snip>[/QUOTE]
No. I'm claiming that [i]no[/i] camera (with a single aperture and focal plane) gives an image that can tell you how far away [i]anything[/i] actually is. You need more information. If there's something in the image whose actual size is known, you can do stuff. Without that sort of information, the picture won't tell you if it's showing a tiny object nearby or a large object far away. An example of the mischief that can be caused by this ambiguity may be seen [url=https://allthatsinteresting.com/famous-fake-photos/2]here[/url].

If you are instead concerned with undoing the distortions caused by a lens, then as already indicated by other posters, it depends on the specific lens. I suggest a Google search with parameters

"fisheye lens correction"

 chris2be8 2019-07-02 15:40

[QUOTE=jasong;520544]I'm certainly not an expert, but if you think about it, everything you see is a 2-d image, a spherical image that impinges on your eyeball.

[/QUOTE]

Most people have two eyes, and comparing the images lets you estimate how far away things are by parallax. And seeing how the image changes as you move relative to the scene lets you estimate 3D shapes as well.

A photograph is just one 2D image, so you have a lot more ambiguity to worry about.

Chris

 Batalov 2019-07-02 22:32

An image, ha! Even a video is not going to tell you the truth:

 a1call 2019-07-02 23:18

Another case and point.
ETA, sorry my video does not upload. I get the message it's invalid.

 Batalov 2019-07-02 23:40

[QUOTE=a1call;520606]Another case and point.
ETA, sorry my video does not upload. I get the message it's invalid.[/QUOTE]
Different countries - different access. I also cannot view many of the videos that other people occasionally post.

Simply google for "The Mysterious Floating Orb" [SPOILER](add Yankovic if needed[/SPOILER].

 a1call 2019-07-02 23:47

I can see your video, no problem. I was trying to upload a video of the object created by the Japanese mathematician.
Here is an article about the object. The video is from the cylinders turning to diamond shape.

[url]https://www.insider.com/optical-illusions-japanese-mathematician-2018-5[/url]