Bob, thanks for the clarification; indeed, I have learned something. We were
on different tacks but I think I was responding to one of the digressions which
are typical with this type of communication. I won't presume to argue optics
with you. Thanks again. Don
Bob Blakely wrote:
> I suspect we are not communicating about the same thing. The question was
> about _viewing_ through a wide angle peephole in a door, not taking
> pictures. Let me quote for you again:
>
> > Does anybody know why the image in an apartment door peep-hole
> > is not inverted? Is there a tiny little penta-prism in there?
>
> When you view images set for film (on your ground glass) through a
> converging lens system, the image is indeed upside down. When you place a
> second converging lens in the system between the first and the image plane
> such that the second focuses on the virtual image from the first and upon
> the film plane the image is indeed "right side up". When you view the images
> through your eye, you use your eye's lens as part of the closer converging
> lens and indeed you do form an image "right side up" on your retina. Now
> here comes the tricky part... Your eye, when used without any lenses forms
> an image "upside down" on your retina! Your brain translates this into the
> _perception_ of "right side up"! Now, that "right side up" image you
> presented to your retina is perceived as, you guessed it, "upside down"!
>
> Are there other ways that the optics (including your eye) can be arranged?
> Yes. They could be arranged as a three convex group system with two virtual
> images, but then I was relating to most normal arrangement of optics and to
> arrangements comparable to the original poster's question. If you wish to
> argue some different arrangement feel free to do so. If you don't change the
> topic you'll confuse the hell out of me though, because I'll be stuck on
> thinking you are still trying to be helpful to the original poster.
>
> Good topic in it's own right, though. It's all about light, and lenses make
> the light form images for us.
>
> Regards,
> Bob...
>
> From: "Don Roberts" <droberts@soli.inav.net>
>
> > Ok, Bob, I have been wrong many times in my life and usually learn from
> the
> > experience. Now would you care to elaborate so that I might profit from
> this
> > one? Are you saying that the construction as I described it is wrong or
> that I
> > can't take the photos that I have taken with such a device? I might have
> to
> > equivocate by saying that I have taken photos through these viewers
> mounted on
> > a lens cap and then mounted in front of a lens. I can't remember for sure
> if I
> > have done it with only a body cap. Don
> >
> > Bob Blakely wrote:
> >
> > > Sorry, You are...
> > > ...wrong where it comes to viewing the image through an eyepiece on the
> > > device.
> > >
> > > Regards,
> > > Bob...
> > >
> > > From: "Don Roberts" <droberts@soli.inav.net>
> > >
> > > > My understanding of this is that there are simply two lenses. The
> first
> > > would
> > > > invert the image and the second would invert it again making it
> rightside
> > > up.
> > > > And I hate to disagree with authority but I have used these things
> mounted
> > > on
> > > > body caps and on lens caps to make surreal fisheye images.
> Don
--
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Don Roberts * Bittersweet Productions * Iowa City, IA
* *
And the Devil whispered behind the leaves, "It's pretty,
but is it Art?". -- Rudyard Kipling
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