Subject:
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Re: Math/Optics Problem
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Newsgroups:
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lugnet.off-topic.geek
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Date:
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Tue, 14 Aug 2001 15:23:55 GMT
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Viewed:
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116 times
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David:
> In lugnet.off-topic.geek, Jacob Sparre Andersen writes:
> > > #2 If not, will it at least be constant for the same zoom level?
> > No.
> >
> > > #3 are there any other "missing pieces" to the formula?
> > Yes: Focus (I think).
> >
> > > #4 what is the formula for figuring out the distance between the two
> > > objects?
> >
> > dist. from camera = (fisheye const.)*(actual height)/(photo
> > height) + (small obscure camera dependent constant)
>
> Hmm... So both the zoom and the focus affect the fisheye constant?
<activate brain/>
Hmmm... Maybe not. The focus is probably rather affecting
the "small obscure" supposedly only "camera dependent"
supposedly "constant".
> How exactly does the focus change it?
I think I have to open a camera (or an optics textbook) and
have a look.
> I guess I'm imagining the same actual
> image in and out of focus and not seeing actual change in the image's shapes
> & relative sizes... which would mean that it *would* be constant for the
> same zoom level? Or am I not figuring something right?
I think you _are_ figuring something right.
> > > #5 can I use that same formula to find out how far away from the *camera*
> > > the objects are?
> >
> > Yes, but then you have to figure out the value of the "small
> > obscure camera dependent constant" .
>
> Just curious-- does this value indicate the distance that the light has to
> travel before hitting the focus point? For example, let's say that there's a
> maze of mirrors accounting for 12 feet of light-travel distance between the
> light entry point of the camera and the final "focal point". Would this
> constant then be somewhere in the vicinity of 12 feet?
Yes, more or less (I think).
The right thing to do is - no matter what - to calibrate
based on known parameters. I have at some point derived the
equations for 3D reconstruction from a collection of images.
That would solve your problem (and a bit more) without
having to care about the actual whereabouts of the camera.
Jacob (who should stick to the kinds of physics he knows)
--
http://hugin.ldraw.org/Jacob/edb/digitale_nyheder
Om redaktørens opgave på internetnyhedstjenester.
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Message is in Reply To:
 | | Re: Math/Optics Problem
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| (...) Hmm... So both the zoom and the focus affect the fisheye constant? How exactly does the focus change it? I guess I'm imagining the same actual image in and out of focus and not seeing actual change in the image's shapes & relative sizes... (...) (23 years ago, 14-Aug-01, to lugnet.off-topic.geek)
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