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Old Feb 9, 2018, 3:49 PM   #1
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Default What does a fish-eye image look like?

Hi,
I imagine that most people would find this a strange question, so I'll explain. Lately I've been interested in fish-eye photography; so I cobbled together, what I thought, would be a fish-eye lens from my store of old lenses. It's definitely a wide angle, but is it fish-eye? I have my doubts. I would have thought a fish-eye image would bulge out more in the center. (I know that the focus is not good). I'm posting a picture.
.... john
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Last edited by Shinnen; Feb 9, 2018 at 3:51 PM. Reason: spelling
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Old Feb 9, 2018, 8:04 PM   #2
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If you want it to bulge out more in the center, you need to get closer. The bulge is the perspective distortion that can occur with any lens short of a telephoto. The amount of the bulge is determined by the subject distance and the degree to which the lens is designed to project a rectilinear image.
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Old Feb 10, 2018, 3:05 PM   #3
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Hi TCav,
Alright. I'll try that.
Thanks,
..... john
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Old Feb 21, 2018, 6:46 PM   #4
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Hi TCav,
After going through my box of old lenses I managed find a combination that produced a 'reasonable' facsimile of a fish-eye lens.
I'm attaching an image that it took.
Thanks again,
.. john
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Old Feb 21, 2018, 9:02 PM   #5
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A very wide angle of view produces a perspective that we don't normally see.

Consider this:
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Old Feb 21, 2018, 10:11 PM   #6
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Hi TCav,
So, what are you saying here?
... john
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Old Feb 22, 2018, 7:09 AM   #7
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Fisheye lenses don't try to produce a rectilinear image like conventional lenses. The bulge you're looking for is a result of the difference distance between the subject in the center of the frame and the camera, and the distance between objects at the edge of the frame and the camera.

Objects that are close appear bigger in the frame, while distant objects appear smaller. A fisheye lens allows you to fit both close and distant portions of the same object in the frame at the same time.
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Old Feb 22, 2018, 7:49 AM   #8
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Ahhh .... OK.
Thanks,
....john
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Old Mar 6, 2018, 6:10 PM   #9
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Conversely, If there are no objects close to the camera, there's no bulge, just a very wide angle of view.

It's the lack of a rectilinear projection that makes the "fish-eye" image.
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Old Mar 6, 2018, 10:06 PM   #10
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Thanks TCav.
I think I get it now.
..... john
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