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Lens Distortion Fisheye HELP

 
 
dude
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      12-07-2004
I am shooting using a fisheye lens (century optics 3x fisheye)
with my sony trv900.

It works but i would like to know if i add distance to the fisheye
lens
to the CCD sensors (In the form of an ring adaptor) what would happen
?

A) Would i retain the same magnitude of fisheye effect with edge
clipping
of what would be the edge without the ring adaptor ?

B) Or would i see a reduced fisheye effect since the lens is further
away
from the CCD sensor.

I am hoping that i see a reduced amount of fisheye.

Currently i have manually at first then using automated script
gotten photoshop to dewarp my images. This process is pain stakingly
SLOW.

If that doesnt work would another fisheye lens that gives me a
slightly
reduced field of horizontal view work ?

My problem is that my lens currently gives me about 125 degree field
of view
and i dewarp to what i believe is close to 115 degress field of view.
I am unable to find a fish eye that gives me a natural 115 degree
field of view which im hoping would be good enough for me not to have
to dewarp.


Any help would be greatly welcome

Tim Bernard.
 
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Michael A. Covington
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      12-07-2004

"dude" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...

> It works but i would like to know if i add distance to the fisheye
> lens
> to the CCD sensors (In the form of an ring adaptor) what would happen
> ?


Try holding it farther out, and see.

> B) Or would i see a reduced fisheye effect since the lens is further
> away
> from the CCD sensor.


Probably an increased fisheye effect.


> I am unable to find a fish eye that gives me a natural 115 degree
> field of view which im hoping would be good enough for me not to have
> to dewarp.


"Fisheye" means "warped image." For lenses with straight lines, you want a
wide-angle lens, not a fisheye lens. I have no idea whether such extreme
wide-angle lenses exist for your camera.


 
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stauffer@usfamily.net
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      12-07-2004
The main thing you would get is defocus. Now, wide FOV lenses have a
great depth of field to start with, so the amount of defocus would not
be as great as with normal lenses.

However, defocus can be considered a relative thing, so moving a lens a
given fraction of the focal length results in a given degree of
defocus. Now, moving the lens away from the focal plane causes its
plane of sharp object focus to move nearer. Unless you have objects in
the field up close, the result will be a general defocus of the distant
background and almost everything else.

A defocus can cause some degree of vignetting which could limit field
of view. But you will not get a sharp cutoff to field.

Cropping would allow you to take only the 115 out of the 125, so
cropping before warping should give you what you seek.

 
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Michael A. Covington
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      12-07-2004
Clarifying what I said earlier:

"fisheye" means "lens that produces curved, distorted images."

A lens that covers a wide field without introducing curvature is called a
wide-angle lens.


 
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