Re: [tech-3d] Digest Number 36

["Don Lopp" <dlopp@xxxxxxxxxxxxxxx>]

To Mike Davis reguarding stereo base- or 20 plus years I have been using a
simple way of figuring out the stereo base for taking hyper scenics. For a
135 mm lens I figure that the base of one foot gives me stereo depth of 135
feet to infinity or five times 135  gives me a stereo depth  of 675 feet to
infinity. For a 75 mm lens , I figure a one foot base gives me  a stereo
depth of from  75 feet to infinity. For a 100 mm lens, a one foot base gives
me a stereo depth of 100 feet to infinity and so on. For a 100 mm lens I
figure that infinity is any thing past 3,000 feet, or 30 times the near
point. I dont try to maximize the stereo effect in my pictues as some of  my
best ones have a deviation of less than one mm. My mental state because of
my use of methadone and morphine is such that I can not handle any thing
very complicated and it has been some 6 months since I have been able to
take any serious scenics-may be next year ? DON
----- Original Message -----
From: <tech-3d@xxxxxxxxxxx>
To: <tech-3d@xxxxxxxxxxx>
Sent: Monday, November 27, 2000 11:39 AM
Subject: [tech-3d] Digest Number 36


>
> There are 2 messages in this issue.
>
> Topics in this digest:
>
>       1. Re: Fw: Your latest ref the Stereo Base formula (to M. Davis)
>            From: boris@xxxxxxxxxxxx
>       2. Re: Digest Number 35
>            From: "Don Lopp" <dlopp@xxxxxxxxxxxxxxx>
>
>
> ________________________________________________________________________
> ________________________________________________________________________
>
> Message: 1
>    Date: Sun, 26 Nov 2000 12:39:39 -0500
>    From: boris@xxxxxxxxxxxx
> Subject: Re: Fw: Your latest ref the Stereo Base formula (to M. Davis)
>
> Allan and friends:
>
> you wrote to me:
> >course, it would be interesting to assess what it is you claim that you
have
> >learned!  I certainly wish I could learn only a slice of what you know
about
>
> Aside from getting the formula, I learned that the retinal deviation may
be
> variable, though the actual on-film (or -screen, or -print) deviation is
> constant and given.  I.e. I learned that viewing parameters for prints are
> analogous for those of stereo slide viewers, and should not be ignored.
>
> >Just as an example, Boris.  I remember you stating that you are a "depth
> >demon".  ...achieved by increasing the allowable on-film deviation ...
> >up to 2.00mm in cases where you can bring some of the subject through the
> >window.  These values don't appear to present a problem in hand viewing.
> >Its with projection, where the real test of what is too much deviation,
>
> Well, my Pixie image, which has minimal window violation in foreground,
has
> something like 3 or 4 mm of deviation.  I've never had anyone complain
> about too much depth - including stereo neophytes, who are less able to
> accomodate extreme depth - and it has won numerous awards (projected).  I
> believe one can sustain greater depths as long as one leads the viewer's
> eye into the depth with some physical guide in the image.  In the case of
> the Pixie that is the plane of water.  Also the objects at greatest depth
> are very pale, so that rivalries (with nearby objects) do not distract as
> much.  Certainly there are other images where less deviation can be
> distracting or difficult to view.
>
> So I totally agree with your intent in this discussion, which is to point
> out that mathematics and formulas alone cannot guarantee good stereo image
> results.  The variables are indeed numerous, and some are not even
numeric!
>
> >
> >When you say that you hope to use this "magic math formula" to help you
> >reduce the amount of "differential" or potential areas of ghosting in
your
> >anaglyphs, this can only be done by reducing your stereo base or on-film
>
> I did not say that.  I said that I want to control depth in anaglyphs.  TO
> design an image for a particular size anaglyph print, you need to vary
your
> taking geometry as appropriate - the equation helps in this work.  (If I
> know an image will be presented in a magazine at three inches wide, to be
> viewed at 1/2 arms length, I need to take a very different shot than if it
> were presented at 30 inches wide, to be viewed from six feet back!)
>
> But since you bring it up, yes I do want to minimize ghosting.  This I
> achieve with composition.  Beyond even minimizing ghosting, I try to hide
> or integrate the deviation in objects of greater depth into the picture,
so
> that it looks good FLAT too.  This is the focus of my current exhibit here
> in Charlottesville.  Just in case you can't visit, you can review my
> (non-math) thesis here:
> http://www.starosta.com/3dshowcase/technobot.html
>
> >matter.  Stereo is like the weather.  The variables are as numerous.
>
> Allan, you had responded to my words:
> >> others, they sounded useful to me.  I am presently exploring variable
> >> stereobase photography to control apparent depth in anaglyphs.
>
> ________________________________________________________________________
> Boris Starosta, 3d artist             boris@xxxxxxxxxxxx
> Dynamic Symmetry, LLC                 http://www.starosta.com
> usa - 804 979 3930                    http://www.starosta.com/3dshowcase
>
> Currently showing at The Observatory. Info: ...3dshowcase/technobot.html
>
>
>
>
> ________________________________________________________________________
> ________________________________________________________________________
>
> Message: 2
>    Date: Mon, 27 Nov 2000 00:05:31 -0800
>    From: "Don Lopp" <dlopp@xxxxxxxxxxxxxxx>
> Subject: Re: Digest Number 35
>
>
> ----- Original Message -----
> From: <tech-3d@xxxxxxxxxxx>
> To: <tech-3d@xxxxxxxxxxx>
> Sent: Saturday, November 25, 2000 3:56 AM
> Subject: [tech-3d] Digest Number 35
>
>
> >
> > There are 2 messages in this issue.
> >
> > Topics in this digest:
> >
> >       1. Re: Digest Number 33
> >            From: "Don Lopp" <dlopp@xxxxxxxxxxxxxxx>
> >       2. Re: Digest Number 33
> >            From: "Don Lopp" <dlopp@xxxxxxxxxxxxxxx>
> >
> >
> > ________________________________________________________________________
> > ________________________________________________________________________
> >
> > Message: 1
> >    Date: Fri, 24 Nov 2000 21:04:50 -0800
> >    From: "Don Lopp" <dlopp@xxxxxxxxxxxxxxx>
> > Subject: Re: Digest Number 33
> >
> >
> > ----- Original Message -----
> > From: <tech-3d@xxxxxxxxxxx>
> > To: <tech-3d@xxxxxxxxxxx>
> > Sent: Thursday, November 23, 2000 12:50 PM
> > Subject: [tech-3d] Digest Number 33
> >
> >
> > >
> > > There are 4 messages in this issue.
> > >
> > > Topics in this digest:
> > >
> > >       1. Re: holographic 3d
> > >            From: lunazzi <lunazzi@xxxxxxxxxxxxxx>
> > >       2. Re: Stereo Base Calculation with a $20.00 Handheld
> > >            From: "Michael K. Davis" <zilch0@xxxxxxxxxxxx>
> > >       3. Why consider ratio of Viwer FL to Camera FL?
> > >            From: "Michael K. Davis" <zilch0@xxxxxxxxxxxx>
> > >       4. Re: Re: Stereo Base Calculation with a $20.00 Handheld
> > >            From: Andres Posada O <aposadao@xxxxxxxxxx>
> > >
> > >
> > >
________________________________________________________________________
> > >
________________________________________________________________________
> > >
> > > Message: 1
> > >    Date: Wed, 22 Nov 2000 15:20:19 -0200
> > >    From: lunazzi <lunazzi@xxxxxxxxxxxxxx>
> > > Subject: Re: holographic 3d
> > >
> > > Peter Homer wrote:
> > >
> > > > >The technique of projecting with mirrors is as old as 4000 years
(the
> > Incas and
> > > > >the Olmecas). I did not think these new world civilisations were as
> old
> > as this
> > > > which is as old or older than anything in the old world and I
thought
> > the Olmecs were the oldest rather than the Incas
> > >
> > > I do not know if they were older than the Incas, the interesting thing
> is
> > that they disappeared before the Aztecs but left a very important
> influence
> > on them. I do not know if Teotihuacan is considered precisely Olmec, but
> it
> > seems to be, and was considered as a sacred city when it was found
> inhabited
> > by the Aztecs.
> > >
> > > > but perhaps that was just in Central rather than South America
> > > > >http://www.geocities.com/Athens/Forum/3853/olm1e.html
> > > > >
> > > > I had a look at this site although I could not view the graphics
> > properly with my my Netscaoe Navigator 2.02,
> > >
> > > Maybe it is due to the version, because I use Netscape 4 now, although
I
> > started with 2.0
> > > I verified by reading from a different terminal than I used for
> editing,
> > to avoid the direct lecture on the computer rather than through internet
> (is
> > a typical error that sometimes arrives to me).
> > >
> > > > I found it very interesting but was the original intention of the
> > concave mirrors to project images or to focuss the suns rays to produce
> > fire,as the name Tezcatlipoca ( smoking Mirror) suggests. Perhaps with a
> > religious significance as the fire was taken directly from the sun,
> > >
> > > This was already made by the Incas, precisely as you wrote, but using
> > metal mirrors.
> > >
> > > > I have seen some other illustrations of these types of mirrors made
> from
> > polished pyrite or iron sulphide FeS2 which can form naturaly in balls
or
> > discs
> > >
> > > I have some samples, but not in the form of balls or discs.
> > >
> > > > consisting of radiating needle like crystals. Specular haematite can
> > also form a miror like surface when polished,
> > > >
> > >
> > > I am trying a technician to made the polishing on them, using aluminum
> > oxide.
> > >
> > > I would like to put more information on my page, including the whole
> > article, but for the moment I can mail you the article if you send me
your
> > postal address.
> > >
> > > > >Projecting on lenses is also interesting, it renders a floating
> image.
> > > > >The progress in this last years shoul be in increasing the field of
> > view, wether
> > > > >using paraboloidal mirrors more specific that the Olmecas ones (as
> > Peter Homer
> > > > >indicated)
> > > >
> > > > P.J.Homer
> > >
> > > The serpent heads emerging in the Teotihuacan temples (pyramides)
arises
> > from mirrors (archeologist said), what shows clearly (at least to me)
that
> > mirrors were employed for imaging.  On the other hand, if they were
merely
> > to concentrate sun,  I can suppose that it did not needed so much
> polishing.
> > Another interesting feature is that most Olmec mirrors has two different
> > focal lenghts (along perpendicular directions) what makes them to not
> > concentrate light in focus.
> > >
> > > José
> > >
> > >
> > >
> > >
________________________________________________________________________
> > >
________________________________________________________________________
> > >
> > > Message: 2
> > >    Date: Wed, 22 Nov 2000 23:31:39 -0600
> > >    From: "Michael K. Davis" <zilch0@xxxxxxxxxxxx>
> > > Subject: Re: Stereo Base Calculation with a $20.00 Handheld
> > >
> > > Abram,
> > >
> > >
> > > >Date: Mon, 20 Nov 2000 15:52:01 -0000
> > > >From: "Abram Klooswyk" <abram.klooswyk@xxxxxx>
> > > >Subject: Re: Stereo Base Calculation With a $20.00 Handheld
> > >
> > > [snip]
> > >
> > > >Michael Davis wonders why I call the so-called "General Solution"
> > > >paradoxical.
> > > >The formula is for base calculation, to get a base which results in
> > > >a viewable deviation. Many newbies like such a rule. However, the
> > > >formula next asks for an _input_ of the deviation which it should
> > > >provide as _outcome_ on film, after _using_ the calculated base.
> > > >Newbies will ask: what deviation?
> > > >You can calculate it from the base, and than get in an endless
> > > >regression. In discussions many different values for deviation are
> > > >mentioned, which isn't particular helpful for newbies.
> > >
> > > There is no paradox.  You could apply your argument to the push-pull
> > > relationship between aperture and shutter speed.  But unlike the
> > > relationship between aperture and shutter speed, where we quite often
> > > toggle between wanting to fix one and solve for the other, any hope of
> > > calling the General Solution a parodox vanishes when we acknowledge
that
> > > Base is on one side of the equal sign, ALL BY ITSELF, and deviation is
> one
> > > of several variables on the other side.
> > >
> > > The General Solution is an equation.  The author had a reasonable
> > > expectation that users would understand they are *solving for base*,
NOT
> > > solving for deviation, not solving for focal length, not solving for
> near
> > > point or far point, etc.  I have yet to see the General Solution
> expressed
> > > as a solution for deviation - with a  d  all by itself on one side of
> the
> > > equal sign and base specified as a variable along with all the others,
> on
> > > the other side of the equation.
> > >
> > > I can't imagine any newbies actually doing the math to rearrange the
> > > General Solution in the first place, much less finding themselves in
an
> > > endless regression, solving for deviation, then for base, then for
> > > deviation, then for base, etc.  Your argument is quite simply
fantastic.
> > >
> > > Everyone I've read about or spoken to who uses the General Solution,
is
> > > completely content to use it for one purpose - solving for base.  Base
> is
> > > the output.
> > >
> > > The formula is used to deliver a base value that will PRODUCE the
> on-film
> > > deviation you have CHOSEN to specify as a variable.  The General
> Solution
> > > can deliver numerous bases, each unique to the scene described by the
> Near
> > > and Far variables, but these bases, though different from one scene to
> the
> > > next will CONSISTENTLY produce the CHOSEN on-film deviation, within
the
> > > range of bases permitted by your equipment and technique, of course.
> > >
> > > It is not at all difficult to select an on-film deviation value that
> > > satisfies your personal taste for how much depth your images will
have.
> > >
> > > My original post, as seen at
> > >
> > > http://www.pauck.de/archive/mailinglist/tech-3d/mhonarc/msg01919.html
> > >
> > > suggests shooting with bases that are calculated using a deviation
equal
> > to
> > > 80% of the Maximum Allowable On-Film Deviation.  I also explained that
> > > MAOFD is just the camera focal length divided by 30.   80% of MAOFD is
> > just
> > > a place to start.  Shoot a few rolls at 80% of MAOFD to get a feel for
> it.
> > > It's subjective.  It's up to you to determine if you find it
appealing.
> > If
> > > 80% of MAOFD is a little too strong for you (too much "bite" for your
> > > taste), try a few rolls at a lesser percentage.  The General Solution
> will
> > > deliver the exact same deviation on-film, every time.  And even if
> you've
> > > found that something like 75% MAOFD suits your needs most of the time,
> > > there's nothing stopping you from CHOOSING more or less depth for a
> > > particular scene you are about to shoot.  You are in control, but it's
> > your
> > > responsibility to get a feel for the numbers.
> > >
> > > [snip]
> > >
> > > >When you want to emphasize tiny scratches on ancient coins, stretch
> > > >might be your purpose. But Michael Davis says:
> > >
> > > >>It is my personal preference to use a variable base,
> > > >>following the General Solution, for nearly every situation,
> > > >>including the mid-field.
> > >
> > > >When this would include a portrait of a person before a nearby
> > > >"backdrop" I'm afraid I would call it weird, to say the least... :-).
> > >
> > >
> > > It is apparent that your intention here is to suggest that in a
> situation
> > > where stretch might be desirable, I would use the General Solution and
> > this
> > > would somehow prohibit that goal.  This assertion is incorrect on two
> > > counts.  First, using the General Solution, I can add stretch at will
by
> > > increasing the deviation used to calculation base.  The General
Solution
> > > does NOT have to be calculated using the Maximum Allowable OFD or any
> > other
> > > fixed value for deviation.  Second, the article from which you quote
> > > clearly states that I abandon the General Solution at Near:Far ratios
> less
> > > than 1:2.  I discuss that at length across several paragraphs. (See
the
> > > link above.) Did you miss that portion of my article or are you just
> > > spinning my words?
> > >
> > > I will vigorously defend your right to prefer more or less on-film
> > > deviation than I do.  I will support your right to select and use
> > equipment
> > > and methodology that YOU find satisfying.  But I can not refrain from
an
> > > equally vigorous defense against absurd attacks on the truth embodied
by
> > > the General Solution.  The formula matches the geometry perfectly.  It
> is
> > > both valid and useful.
> > >
> > > Why must there be a steady onslaught of condemnation for something so
> > > unambigous?   I'm convinced it's mostly just a matter of:
> > >
> > > ignorance (I don't know how to use it so I hate it.)
> > > arrogance (My many years experience have canonized my techniques.)
> > > pride (I will never admit I'm wrong about other people's techniques.)
> > > laziness (I'll just burn a lot of film and see what I get.)
> > > contentiousness (I live to stomp on other people.)
> > >
> > > or some combination of the above.
> > >
> > > Mike Davis
> > >
> > >
> > >
> > >
________________________________________________________________________
> > >
________________________________________________________________________
> > >
> > > Message: 3
> > >    Date: Wed, 22 Nov 2000 23:58:50 -0600
> > >    From: "Michael K. Davis" <zilch0@xxxxxxxxxxxx>
> > > Subject: Why consider ratio of Viwer FL to Camera FL?
> > >
> > > Hi Boris,
> > >
> > > >Date: Mon, 20 Nov 2000 17:33:48 -0500
> > > >From: boris@xxxxxxxxxxxx
> > > >Subject: Re: Stereo Base Calculation With a $20.00 Handheld
> > >
> > > [snip]
> > >
> > > >I have a question.  Why does a viewing device focal length (i.e. a
> > viewing
> > > >geometry) even come into play?  On film deviation is the product
simply
> > of
> > > >camera optics, stereobase, and near and far point.  Why the viewer
> F.L.?
> > > >Granted, the viewer optics affect the perceived depth, but it
certainly
> > > >does not change OFD.
> > > >
> > > >(And for my application, in shooting for anaglyphs, there is no
viewer
> > F.L.
> > > >There may be a print size, and a viewer's naked eye distance to
print -
> > > >that would form the equivalent to a viewer's focal length.  But to
> shoot
> > > >for a specific size anaglyph print, and therein a specific deviation
on
> > > >paper, I want to predict and set up a shot simply for a particular
> > > >deviation on film.  Viewer optics are not otherwise considered.)
> > > >
> > > >Boris
> > >
> > > If you already know an on-film deviation that gives you the look you
> like,
> > > using whatever display mechanism you employ, then you need not be
> > concerned
> > > about compensating a mismatch between viewer focal length and camera
> focal
> > > length.
> > >
> > > I include this ratio of vFL to cFL as a factor in calculating base
> because
> > > just as sitting in the front row of a 3D theater causes squash not
> > > experienced in the middle row, my camera lenses, being of shorter
focal
> > > length than my viewer lenses cause that same squash.  Increasing the
> base
> > > proportionately compensates this.
> > >
> > > I have a closeup 2D picture of my dog's face shot with an 18mm lens
(on
> a
> > > 35mm body).  His nose is nearly the width of his forehead.  Viewed at
a
> > > distance of ten feet, he looks comical in this picture.  But if you
view
> > > the print at a distance equal to the camera focal length times the
> > > enlargement factor, (about 8 inches for this 11x14 print), his
> proportions
> > > appear to be normal.
> > >
> > > Mike
> > >
> > >
> > >
> > >
________________________________________________________________________
> > >
________________________________________________________________________
> > >
> > > Message: 4
> > >    Date: Thu, 23 Nov 2000 08:04:25 -0500
> > >    From: Andres Posada O <aposadao@xxxxxxxxxx>
> > > Subject: Re: Re: Stereo Base Calculation with a $20.00 Handheld
> > >
> > >
> > >
> > > "Michael K. Davis" wrote:
> > > >
> > > >
> > > > The General Solution is an equation.  The author had a reasonable
> > > > expectation that users would understand they are *solving for base*,
> NOT
> > > > solving for deviation, not solving for focal length, not solving for
> > near
> > > > point or far point, etc.
> > > >
> > > > Everyone I've read about or spoken to who uses the General Solution,
> is
> > > > completely content to use it for one purpose - solving for base.
Base
> > is
> > > > the output.
> > > >
> > >
> > > Michael:
> > >    In my HP48G+ I can solve for what ever I want (anybody with the
> > > formulas in a computer or the like may obviopusly do it). Doing 3D
video
> > > I am usually stuck to minimum camera separations, dictated by the
camera
> > > sizes, that require that I solve for near point, sometimes I need to
> > > solve for far point. For example: if I have a minumum camera
separation
> > > due to camera size of say 165mm, and the nearest object is going to be
> > > at 3000mm, then how far may the farthest object be, all this subjected
> > > to a MOFD choosen according to CCD size, lens focal length and TASTE.
> > > What happens to the near point if I change the focal length position
in
> > > the cameras zoom lenses? Everything changes if I use 1/3", 1/2", or
3/4"
> > > CCDs cameras. MOFD numbers I change according obviously to CCD size,
but
> > > also I use more "liberal" numbers if all subjects are inside the
window,
> > > be more conservative with subjects way out of the window and near to
the
> > > camera. My point is I almost never solve for base.
> > >
> > >
> > >
________________________________________________________________________
> > >
________________________________________________________________________
> > >
> > >
> > >
> > >
> >
> >
> >
> > ________________________________________________________________________
> > ________________________________________________________________________
> >
> > Message: 2
> >    Date: Fri, 24 Nov 2000 21:20:16 -0800
> >    From: "Don Lopp" <dlopp@xxxxxxxxxxxxxxx>
> > Subject: Re: Digest Number 33
> >
> > Having built 10 MF viewers with lenses with focal legths of from 45mm to
> > 80mm., I have come to the conclusion that shorter is better. An example
is
> > that I prefer to view  80mm stereo slides with viewer lenses of about
50mm
> > because this makes the views look like Eyemax which is more than I can
say
> > about viewing 35 mm stereo when using the standard available viewers
which
> ,
> > mostly, have lenses of 42 to 45 mm lenses. My viewer with 28mm lenses is
> > pretty good, but I wish I could find some 24 mm lenses that are useable
?
> > DON
> > ----- Original Message -----
> > From: <tech-3d@xxxxxxxxxxx>
> > To: <tech-3d@xxxxxxxxxxx>
> > Sent: Thursday, November 23, 2000 12:50 PM
> > Subject: [tech-3d] Digest Number 33
> >
> >
> > >
> > > There are 4 messages in this issue.
> > >
> > > Topics in this digest:
> > >
> > >       1. Re: holographic 3d
> > >            From: lunazzi <lunazzi@xxxxxxxxxxxxxx>
> > >       2. Re: Stereo Base Calculation with a $20.00 Handheld
> > >            From: "Michael K. Davis" <zilch0@xxxxxxxxxxxx>
> > >       3. Why consider ratio of Viwer FL to Camera FL?
> > >            From: "Michael K. Davis" <zilch0@xxxxxxxxxxxx>
> > >       4. Re: Re: Stereo Base Calculation with a $20.00 Handheld
> > >            From: Andres Posada O <aposadao@xxxxxxxxxx>
> > >
> > >
> > >
________________________________________________________________________
> > >
________________________________________________________________________
> > >
> > > Message: 1
> > >    Date: Wed, 22 Nov 2000 15:20:19 -0200
> > >    From: lunazzi <lunazzi@xxxxxxxxxxxxxx>
> > > Subject: Re: holographic 3d
> > >
> > > Peter Homer wrote:
> > >
> > > > >The technique of projecting with mirrors is as old as 4000 years
(the
> > Incas and
> > > > >the Olmecas). I did not think these new world civilisations were as
> old
> > as this
> > > > which is as old or older than anything in the old world and I
thought
> > the Olmecs were the oldest rather than the Incas
> > >
> > > I do not know if they were older than the Incas, the interesting thing
> is
> > that they disappeared before the Aztecs but left a very important
> influence
> > on them. I do not know if Teotihuacan is considered precisely Olmec, but
> it
> > seems to be, and was considered as a sacred city when it was found
> inhabited
> > by the Aztecs.
> > >
> > > > but perhaps that was just in Central rather than South America
> > > > >http://www.geocities.com/Athens/Forum/3853/olm1e.html
> > > > >
> > > > I had a look at this site although I could not view the graphics
> > properly with my my Netscaoe Navigator 2.02,
> > >
> > > Maybe it is due to the version, because I use Netscape 4 now, although
I
> > started with 2.0
> > > I verified by reading from a different terminal than I used for
> editing,
> > to avoid the direct lecture on the computer rather than through internet
> (is
> > a typical error that sometimes arrives to me).
> > >
> > > > I found it very interesting but was the original intention of the
> > concave mirrors to project images or to focuss the suns rays to produce
> > fire,as the name Tezcatlipoca ( smoking Mirror) suggests. Perhaps with a
> > religious significance as the fire was taken directly from the sun,
> > >
> > > This was already made by the Incas, precisely as you wrote, but using
> > metal mirrors.
> > >
> > > > I have seen some other illustrations of these types of mirrors made
> from
> > polished pyrite or iron sulphide FeS2 which can form naturaly in balls
or
> > discs
> > >
> > > I have some samples, but not in the form of balls or discs.
> > >
> > > > consisting of radiating needle like crystals. Specular haematite can
> > also form a miror like surface when polished,
> > > >
> > >
> > > I am trying a technician to made the polishing on them, using aluminum
> > oxide.
> > >
> > > I would like to put more information on my page, including the whole
> > article, but for the moment I can mail you the article if you send me
your
> > postal address.
> > >
> > > > >Projecting on lenses is also interesting, it renders a floating
> image.
> > > > >The progress in this last years shoul be in increasing the field of
> > view, wether
> > > > >using paraboloidal mirrors more specific that the Olmecas ones (as
> > Peter Homer
> > > > >indicated)
> > > >
> > > > P.J.Homer
> > >
> > > The serpent heads emerging in the Teotihuacan temples (pyramides)
arises
> > from mirrors (archeologist said), what shows clearly (at least to me)
that
> > mirrors were employed for imaging.  On the other hand, if they were
merely
> > to concentrate sun,  I can suppose that it did not needed so much
> polishing.
> > Another interesting feature is that most Olmec mirrors has two different
> > focal lenghts (along perpendicular directions) what makes them to not
> > concentrate light in focus.
> > >
> > > José
> > >
> > >
> > >
> > >
________________________________________________________________________
> > >
________________________________________________________________________
> > >
> > > Message: 2
> > >    Date: Wed, 22 Nov 2000 23:31:39 -0600
> > >    From: "Michael K. Davis" <zilch0@xxxxxxxxxxxx>
> > > Subject: Re: Stereo Base Calculation with a $20.00 Handheld
> > >
> > > Abram,
> > >
> > >
> > > >Date: Mon, 20 Nov 2000 15:52:01 -0000
> > > >From: "Abram Klooswyk" <abram.klooswyk@xxxxxx>
> > > >Subject: Re: Stereo Base Calculation With a $20.00 Handheld
> > >
> > > [snip]
> > >
> > > >Michael Davis wonders why I call the so-called "General Solution"
> > > >paradoxical.
> > > >The formula is for base calculation, to get a base which results in
> > > >a viewable deviation. Many newbies like such a rule. However, the
> > > >formula next asks for an _input_ of the deviation which it should
> > > >provide as _outcome_ on film, after _using_ the calculated base.
> > > >Newbies will ask: what deviation?
> > > >You can calculate it from the base, and than get in an endless
> > > >regression. In discussions many different values for deviation are
> > > >mentioned, which isn't particular helpful for newbies.
> > >
> > > There is no paradox.  You could apply your argument to the push-pull
> > > relationship between aperture and shutter speed.  But unlike the
> > > relationship between aperture and shutter speed, where we quite often
> > > toggle between wanting to fix one and solve for the other, any hope of
> > > calling the General Solution a parodox vanishes when we acknowledge
that
> > > Base is on one side of the equal sign, ALL BY ITSELF, and deviation is
> one
> > > of several variables on the other side.
> > >
> > > The General Solution is an equation.  The author had a reasonable
> > > expectation that users would understand they are *solving for base*,
NOT
> > > solving for deviation, not solving for focal length, not solving for
> near
> > > point or far point, etc.  I have yet to see the General Solution
> expressed
> > > as a solution for deviation - with a  d  all by itself on one side of
> the
> > > equal sign and base specified as a variable along with all the others,
> on
> > > the other side of the equation.
> > >
> > > I can't imagine any newbies actually doing the math to rearrange the
> > > General Solution in the first place, much less finding themselves in
an
> > > endless regression, solving for deviation, then for base, then for
> > > deviation, then for base, etc.  Your argument is quite simply
fantastic.
> > >
> > > Everyone I've read about or spoken to who uses the General Solution,
is
> > > completely content to use it for one purpose - solving for base.  Base
> is
> > > the output.
> > >
> > > The formula is used to deliver a base value that will PRODUCE the
> on-film
> > > deviation you have CHOSEN to specify as a variable.  The General
> Solution
> > > can deliver numerous bases, each unique to the scene described by the
> Near
> > > and Far variables, but these bases, though different from one scene to
> the
> > > next will CONSISTENTLY produce the CHOSEN on-film deviation, within
the
> > > range of bases permitted by your equipment and technique, of course.
> > >
> > > It is not at all difficult to select an on-film deviation value that
> > > satisfies your personal taste for how much depth your images will
have.
> > >
> > > My original post, as seen at
> > >
> > > http://www.pauck.de/archive/mailinglist/tech-3d/mhonarc/msg01919.html
> > >
> > > suggests shooting with bases that are calculated using a deviation
equal
> > to
> > > 80% of the Maximum Allowable On-Film Deviation.  I also explained that
> > > MAOFD is just the camera focal length divided by 30.   80% of MAOFD is
> > just
> > > a place to start.  Shoot a few rolls at 80% of MAOFD to get a feel for
> it.
> > > It's subjective.  It's up to you to determine if you find it
appealing.
> > If
> > > 80% of MAOFD is a little too strong for you (too much "bite" for your
> > > taste), try a few rolls at a lesser percentage.  The General Solution
> will
> > > deliver the exact same deviation on-film, every time.  And even if
> you've
> > > found that something like 75% MAOFD suits your needs most of the time,
> > > there's nothing stopping you from CHOOSING more or less depth for a
> > > particular scene you are about to shoot.  You are in control, but it's
> > your
> > > responsibility to get a feel for the numbers.
> > >
> > > [snip]
> > >
> > > >When you want to emphasize tiny scratches on ancient coins, stretch
> > > >might be your purpose. But Michael Davis says:
> > >
> > > >>It is my personal preference to use a variable base,
> > > >>following the General Solution, for nearly every situation,
> > > >>including the mid-field.
> > >
> > > >When this would include a portrait of a person before a nearby
> > > >"backdrop" I'm afraid I would call it weird, to say the least... :-).
> > >
> > >
> > > It is apparent that your intention here is to suggest that in a
> situation
> > > where stretch might be desirable, I would use the General Solution and
> > this
> > > would somehow prohibit that goal.  This assertion is incorrect on two
> > > counts.  First, using the General Solution, I can add stretch at will
by
> > > increasing the deviation used to calculation base.  The General
Solution
> > > does NOT have to be calculated using the Maximum Allowable OFD or any
> > other
> > > fixed value for deviation.  Second, the article from which you quote
> > > clearly states that I abandon the General Solution at Near:Far ratios
> less
> > > than 1:2.  I discuss that at length across several paragraphs. (See
the
> > > link above.) Did you miss that portion of my article or are you just
> > > spinning my words?
> > >
> > > I will vigorously defend your right to prefer more or less on-film
> > > deviation than I do.  I will support your right to select and use
> > equipment
> > > and methodology that YOU find satisfying.  But I can not refrain from
an
> > > equally vigorous defense against absurd attacks on the truth embodied
by
> > > the General Solution.  The formula matches the geometry perfectly.  It
> is
> > > both valid and useful.
> > >
> > > Why must there be a steady onslaught of condemnation for something so
> > > unambigous?   I'm convinced it's mostly just a matter of:
> > >
> > > ignorance (I don't know how to use it so I hate it.)
> > > arrogance (My many years experience have canonized my techniques.)
> > > pride (I will never admit I'm wrong about other people's techniques.)
> > > laziness (I'll just burn a lot of film and see what I get.)
> > > contentiousness (I live to stomp on other people.)
> > >
> > > or some combination of the above.
> > >
> > > Mike Davis
> > >
> > >
> > >
> > >
________________________________________________________________________
> > >
________________________________________________________________________
> > >
> > > Message: 3
> > >    Date: Wed, 22 Nov 2000 23:58:50 -0600
> > >    From: "Michael K. Davis" <zilch0@xxxxxxxxxxxx>
> > > Subject: Why consider ratio of Viwer FL to Camera FL?
> > >
> > > Hi Boris,
> > >
> > > >Date: Mon, 20 Nov 2000 17:33:48 -0500
> > > >From: boris@xxxxxxxxxxxx
> > > >Subject: Re: Stereo Base Calculation With a $20.00 Handheld
> > >
> > > [snip]
> > >
> > > >I have a question.  Why does a viewing device focal length (i.e. a
> > viewing
> > > >geometry) even come into play?  On film deviation is the product
simply
> > of
> > > >camera optics, stereobase, and near and far point.  Why the viewer
> F.L.?
> > > >Granted, the viewer optics affect the perceived depth, but it
certainly
> > > >does not change OFD.
> > > >
> > > >(And for my application, in shooting for anaglyphs, there is no
viewer
> > F.L.
> > > >There may be a print size, and a viewer's naked eye distance to
print -
> > > >that would form the equivalent to a viewer's focal length.  But to
> shoot
> > > >for a specific size anaglyph print, and therein a specific deviation
on
> > > >paper, I want to predict and set up a shot simply for a particular
> > > >deviation on film.  Viewer optics are not otherwise considered.)
> > > >
> > > >Boris
> > >
> > > If you already know an on-film deviation that gives you the look you
> like,
> > > using whatever display mechanism you employ, then you need not be
> > concerned
> > > about compensating a mismatch between viewer focal length and camera
> focal
> > > length.
> > >
> > > I include this ratio of vFL to cFL as a factor in calculating base
> because
> > > just as sitting in the front row of a 3D theater causes squash not
> > > experienced in the middle row, my camera lenses, being of shorter
focal
> > > length than my viewer lenses cause that same squash.  Increasing the
> base
> > > proportionately compensates this.
> > >
> > > I have a closeup 2D picture of my dog's face shot with an 18mm lens
(on
> a
> > > 35mm body).  His nose is nearly the width of his forehead.  Viewed at
a
> > > distance of ten feet, he looks comical in this picture.  But if you
view
> > > the print at a distance equal to the camera focal length times the
> > > enlargement factor, (about 8 inches for this 11x14 print), his
> proportions
> > > appear to be normal.
> > >
> > > Mike
> > >
> > >
> > >
> > >
________________________________________________________________________
> > >
________________________________________________________________________
> > >
> > > Message: 4
> > >    Date: Thu, 23 Nov 2000 08:04:25 -0500
> > >    From: Andres Posada O <aposadao@xxxxxxxxxx>
> > > Subject: Re: Re: Stereo Base Calculation with a $20.00 Handheld
> > >
> > >
> > >
> > > "Michael K. Davis" wrote:
> > > >
> > > >
> > > > The General Solution is an equation.  The author had a reasonable
> > > > expectation that users would understand they are *solving for base*,
> NOT
> > > > solving for deviation, not solving for focal length, not solving for
> > near
> > > > point or far point, etc.
> > > >
> > > > Everyone I've read about or spoken to who uses the General Solution,
> is
> > > > completely content to use it for one purpose - solving for base.
Base
> > is
> > > > the output.
> > > >
> > >
> > > Michael:
> > >    In my HP48G+ I can solve for what ever I want (anybody with the
> > > formulas in a computer or the like may obviopusly do it). Doing 3D
video
> > > I am usually stuck to minimum camera separations, dictated by the
camera
> > > sizes, that require that I solve for near point, sometimes I need to
> > > solve for far point. For example: if I have a minumum camera
separation
> > > due to camera size of say 165mm, and the nearest object is going to be
> > > at 3000mm, then how far may the farthest object be, all this subjected
> > > to a MOFD choosen according to CCD size, lens focal length and TASTE.
> > > What happens to the near point if I change the focal length position
in
> > > the cameras zoom lenses? Everything changes if I use 1/3", 1/2", or
3/4"
> > > CCDs cameras. MOFD numbers I change according obviously to CCD size,
but
> > > also I use more "liberal" numbers if all subjects are inside the
window,
> > > be more conservative with subjects way out of the window and near to
the
> > > camera. My point is I almost never solve for base.
> > >
> > >
> > >
________________________________________________________________________
> > >
________________________________________________________________________
> > >
> > >
> > >
> > >
> >
> >
> >
> > ________________________________________________________________________
> > ________________________________________________________________________
> >
> >
> >
> >
>
>
>
> ________________________________________________________________________
> ________________________________________________________________________
>
>
>
>


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