I cross-posted this to the RBT S1 group.

Can someone comment on a comparison between viewing the best images
from the best 35mm camera (our beloved S1) as seen in a Comby viewer,
vs the best images of the medium format camera (3D World Medium Format
Camera) as viewed in the best medium format viewer (What is that?).

Thanks,

Grant

How about in projection?

Grant

>
> Can someone comment on a comparison between viewing the best images
> from the best 35mm camera (our beloved S1) as seen in a Comby viewer,
> vs the best images of the medium format camera (3D World Medium Format
> Camera) as viewed in the best medium format viewer (What is that?).
>

Lots of issues to make the comparison,
but I will give it a go....

RESOLUTION between formats - The MF format in general is a genuine
sweet spot for stereo photography, as the gains in on-film resolution
are only slightly degraded by apt. diffraction, due to MF's use of
longer fl's lenses for the same composure. However, the next jump up
to 4x5, has a much less linear gain, due to apt. diffraction becoming a
more significant factor to the venerable 1/R formula, which dictates how
much resolution will be resolved on film. In the case of the 3D World
Camera, its 80mm lenses seem superb, at least from the few slides I
viewed. However, unlike the RBT, you are limited to that fl, unless
you can hack together some wider fl's like a few list members did here
with 55mm lenses. The downside for MF stereo capture, is shutter
speed, for the same composure, same DOF, you loose two stops of shutter
speed...sometimes this is important, based on the subject matter you shoot.


Recording resolution on film is half the game, seeing that resolution in
a viewer is the other half. Once again here, the MF wins. The reason
is....both formats hold approx. the same on-film resolution (all else
being equal, such as quality of lenses, film type, film speed, etc.).
However, when compare them at the same size, you must double the RBT
film to match the MF size film, which in return, will half the
resolution of the smaller film after you enlarge it. So MF will
record almost 2x the resolution. (I am leaving out small details to
keep the comparison simple, such as exact format sizes comparisons, lens
quality issues, small differences in diffraction, etc.)


Next, the viewers.... here is where the mystery part of the craft
begins.... In short, the MF viewer requires only half the magnification
to produce the same size virtual view (the view projected on your
retina) as the Combi. But in reality, the combi with 50mm lenses,
provides approx. 5x magnification, vs. 3.3x with the 3d World viewer.
However, considering the MF has 2x the film size, you can multiply its
3.3 lenses by 2x, or 6.6x. So the virtual view of the MF viewer is
approx. 6.6/5 = 1.32x larger virtual view. A simple, real world
example is, comparing a 10" square print, vs. a 13.2" print, both viewed
at the same distance. So once again, in the area of immersion, or AFOV
(Apparent Field Of View), the MF wins again, and this considers the best
35mm viewer available today, which is about 10x the price of the 3d
world viewer.


Next is the optics in the viewer.... Because the MF viewer is only
enlarging 3.3x, a very simple doublet is used, which has decent
resolving power for such a low cost lens. Compare this with the 3
element combi lens, which are good, but not great IMO. It's not
possible to produce this level of magnification with the needed FOV with
only 3 elements. A min. of 5 elements, maybe up to 8 would be required
to produce a higher resolving and a less distorted lens. The point
here is, the MF viewer wins by default, due to the lower magnification
required, since the longer fl camera lens is doing a lot of the
magnification for you during the image capture process....and camera
lenses are easier to design than magnifiers (viewer lenses) Over all,
I would suggest the 3d world doublet has a better MTF profile, vs. the
Combi lens. Combine this with the added resolution in the film itself,
and the MF wins hand down. Probably by a factor of 2 - 2.5x. And
based on your age and quality of your retinas, in almost all cases, the
retina will have 2 - 5x more potential resolving power than either of
these viewing systems can deliver, therefore, more resolution IS VERY
discernible. In other words, the eye / retina resolution capacity is
not the limiting factor here.


The other factor is back lighting.... A big ingredient of perceiving
resolution is contrast, and contrast is a function of the the lenses
MTF, the film (which should be equal here) and the quality and intensity
of the back light. brighter light = more perceived resolution. The
3d world viewer has no back light, however, they do make a mounting jig
which does have a nice LED back light, and if you jury rig it into a
viewer, it becomes a superb viewer...probably the best commercially
available one today, specially considering its meager price of <$200
IIRC. Dr. T on this list sells 3d world products....


The other critical factors in the viewing process is the particulars of
the persons eyesight.


First, IPD spacing. The 3d world viewer is fixed at about 64mm inter
ocular center lens spacing. It's not adjustable. If you have +/- 1mm
spacing for each eye, the view IMO would still be acceptable, so 62 -
66mm. These lenses are small, and have very restrictive eye placement
leeway - a consequence of keeping the lenses very low cost. The Combi
viewer has lenses that adjust to accommodate IPD spacing, however, the
film remains fixed. If you have a wider IPD than the widest spacing in
the views, often you are subjected to a bit more of convergence than is
natural, however, it's not very uncomfortable - but surely not natural,
i.e. we normally don't converge our eyes to see infinity points in the
real world.


However, if you have shorter IPD, then your eyes are often forced to
diverge a bit, which makes it uncomfortable for some.... (based on how
much divergence, and how young / flexible your eyes are) Regardless,
divergence produces a confusing depth cue to the brain, as we don't
diverge our eyes in the real world, unless you are trying to imitate a
chameleon or a lizard during a game of charades. :-)


Next is focus. If you can focus at infinity, or near infinity, the 3d
world viewer will suffice. However, their mounting jig has a focusing
system, which greatly increases the audience that can use the viewer
without using their corrective eye wear. This is very significant,
because the 3d would doublet lens has extremely small Eye Relief
(ER). ER is the distance from the glass, where all the sharpest
design rays converge and where no vignetting of the image occurs.
Pulling further back from the ER position, will cause vignetting, or
clipping of the image and unfortunately, much increased resolution
degradation. All magnifiers can only be designed for the subject
plane and image plane to be at one position.... from there, image
quality degrades, until you get into much more sophisticated
multi-element optics.... hence why the 3d world viewer is designed for
Non EG wearers, as its ER is very short, probably under 10mm. If you
project a collimated light source behind the film, you could measure it,
but I never bothered. The Combi viewer ER is very short also, not sure
if a spec was offered on their web site, but I would guess near 10mm also.


An ideal stereo viewer would allow about 20mm ER, for both EG and Non
EG wearers, similar to the optics in higher end binoculars. But no such
viewer exists. So the 3d world mounting jig solves this issue for
those with a relatively tight refractive errors, assuming the errors are
equal in each eye, because the viewer focuses both lenses on the same
plane. However, those with strong refractive errors, or mismatch
refractive errors, or astigmatisms - are forced to wear the corrective
eye wear. Combi viewer does focus each eye separately, but it is very
sensitive to eye rotation.... as the lenses are ultra sensitive to eye
position...if the pupil is the slightest bit off-center axis, distortion
is entered into one eye, or both....often setting up binocular rivalry -
and usually a headache or dizziness shortly thereafter. Quite the
challenge.... But for 35mm film, if your IPD is not less than say
64mm, its the best viewer on the market IMO. They also offer the 45mm
lenses....but ....


Bottom line..... 35mm stereo photography has just a few advantages over
MF. Currently, the line of RBT cameras allow for interchangeable lens
fl's, a nice benefit. For the same composure / same DOF, you will gain
2 stops of shutter speed, sometimes this is mandatory. The gear is
MUCH smaller and lighter. Film is cheaper. A ton of viewers are
available off -the-shelf. Other than these issues, i can't think of
any other advantages of 35mm stereo. Well, maybe more people use it,
so you can share views with more people.... But for max. WOW factor,
MF is clearly the winner.

Hope this helps!

Thank you for the thorough reply!!

The RBT S1 has the same lens separation as my eyes, 59mm, and it
does not have interchangeable or zooming lenses.

My viewer was handmade by the inimitable Don Lopp, and has Comby
lenses. It is focusable and has interoccular adjustments.

Thanks,

Grant

--- In MF3D-group@yahoogroups.com, Bill G wrote:
>
> Grant
> >
> > Can someone comment on a comparison between viewing the best
images
> > from the best 35mm camera (our beloved S1) as seen in a Comby
viewer,
> > vs the best images of the medium format camera (3D World Medium
Format
> > Camera) as viewed in the best medium format viewer (What is
that?).
> >
> Lots of issues to make the
comparison,
> but I will give it a go....
>
> RESOLUTION between formats - The MF format in general is a
genuine
> sweet spot for stereo photography, as the gains in on-film
resolution
> are only slightly degraded by apt. diffraction, due to MF's use of
> longer fl's lenses for the same composure. However, the next
jump up
> to 4x5, has a much less linear gain, due to apt. diffraction
becoming a
> more significant factor to the venerable 1/R formula, which
dictates how
> much resolution will be resolved on film. In the case of the 3D
World
> Camera, its 80mm lenses seem superb, at least from the few slides
I
> viewed. However, unlike the RBT, you are limited to that fl,
unless
> you can hack together some wider fl's like a few list members did
here
> with 55mm lenses. The downside for MF stereo capture, is
shutter
> speed, for the same composure, same DOF, you loose two stops of
shutter
> speed...sometimes this is important, based on the subject matter
you shoot.
>
>
> Recording resolution on film is half the game, seeing that
resolution in
> a viewer is the other half. Once again here, the MF wins. The
reason
> is....both formats hold approx. the same on-film resolution (all
else
> being equal, such as quality of lenses, film type, film speed,
etc.).
> However, when compare them at the same size, you must double the
RBT
> film to match the MF size film, which in return, will half the
> resolution of the smaller film after you enlarge it. So MF
will
> record almost 2x the resolution. (I am leaving out small details
to
> keep the comparison simple, such as exact format sizes
comparisons, lens
> quality issues, small differences in diffraction, etc.)
>
>
> Next, the viewers.... here is where the mystery part of the craft
> begins.... In short, the MF viewer requires only half the
magnification
> to produce the same size virtual view (the view projected on your
> retina) as the Combi. But in reality, the combi with 50mm
lenses,
> provides approx. 5x magnification, vs. 3.3x with the 3d World
viewer.
> However, considering the MF has 2x the film size, you can multiply
its
> 3.3 lenses by 2x, or 6.6x. So the virtual view of the MF viewer
is
> approx. 6.6/5 = 1.32x larger virtual view. A simple, real world
> example is, comparing a 10" square print, vs. a 13.2" print, both
viewed
> at the same distance. So once again, in the area of immersion,
or AFOV
> (Apparent Field Of View), the MF wins again, and this considers
the best
> 35mm viewer available today, which is about 10x the price of the
3d
> world viewer.
>
>
> Next is the optics in the viewer.... Because the MF viewer is
only
> enlarging 3.3x, a very simple doublet is used, which has decent
> resolving power for such a low cost lens. Compare this with the
3
> element combi lens, which are good, but not great IMO. It's not
> possible to produce this level of magnification with the needed
FOV with
> only 3 elements. A min. of 5 elements, maybe up to 8 would be
required
> to produce a higher resolving and a less distorted lens. The
point
> here is, the MF viewer wins by default, due to the lower
magnification
> required, since the longer fl camera lens is doing a lot of the
> magnification for you during the image capture process....and
camera
> lenses are easier to design than magnifiers (viewer lenses)
Over all,
> I would suggest the 3d world doublet has a better MTF profile,
vs. the
> Combi lens. Combine this with the added resolution in the film
itself,
> and the MF wins hand down. Probably by a factor of 2 - 2.5x.
And
> based on your age and quality of your retinas, in almost all
cases, the
> retina will have 2 - 5x more potential resolving power than either
of
> these viewing systems can deliver, therefore, more resolution IS
VERY
> discernible. In other words, the eye / retina resolution
capacity is
> not the limiting factor here.
>
>
> The other factor is back lighting.... A big ingredient of
perceiving
> resolution is contrast, and contrast is a function of the the
lenses
> MTF, the film (which should be equal here) and the quality and
intensity
> of the back light. brighter light = more perceived
resolution. The
> 3d world viewer has no back light, however, they do make a
mounting jig
> which does have a nice LED back light, and if you jury rig it into
a
> viewer, it becomes a superb viewer...probably the best
commercially
> available one today, specially considering its meager price of
<$200
> IIRC. Dr. T on this list sells 3d world products....
>
>
> The other critical factors in the viewing process is the
particulars of
> the persons eyesight.
>
>
> First, IPD spacing. The 3d world viewer is fixed at about 64mm
inter
> ocular center lens spacing. It's not adjustable. If you have
+/- 1mm
> spacing for each eye, the view IMO would still be acceptable, so
62 -
> 66mm. These lenses are small, and have very restrictive eye
placement
> leeway - a consequence of keeping the lenses very low cost. The
Combi
> viewer has lenses that adjust to accommodate IPD spacing,
however, the
> film remains fixed. If you have a wider IPD than the widest
spacing in
> the views, often you are subjected to a bit more of convergence
than is
> natural, however, it's not very uncomfortable - but surely not
natural,
> i.e. we normally don't converge our eyes to see infinity points in
the
> real world.
>
>
> However, if you have shorter IPD, then your eyes are often forced
to
> diverge a bit, which makes it uncomfortable for some.... (based on
how
> much divergence, and how young / flexible your eyes are)
Regardless,
> divergence produces a confusing depth cue to the brain, as we
don't
> diverge our eyes in the real world, unless you are trying to
imitate a
> chameleon or a lizard during a game of charades. :-)
>
>
> Next is focus. If you can focus at infinity, or near infinity,
the 3d
> world viewer will suffice. However, their mounting jig has a
focusing
> system, which greatly increases the audience that can use the
viewer
> without using their corrective eye wear. This is very
significant,
> because the 3d would doublet lens has extremely small Eye Relief
> (ER). ER is the distance from the glass, where all the sharpest
> design rays converge and where no vignetting of the image
occurs.
> Pulling further back from the ER position, will cause vignetting,
or
> clipping of the image and unfortunately, much increased resolution
> degradation. All magnifiers can only be designed for the
subject
> plane and image plane to be at one position.... from there, image
> quality degrades, until you get into much more sophisticated
> multi-element optics.... hence why the 3d world viewer is designed
for
> Non EG wearers, as its ER is very short, probably under 10mm. If
you
> project a collimated light source behind the film, you could
measure it,
> but I never bothered. The Combi viewer ER is very short also,
not sure
> if a spec was offered on their web site, but I would guess near
10mm also.
>
>
> An ideal stereo viewer would allow about 20mm ER, for both EG and
Non
> EG wearers, similar to the optics in higher end binoculars. But
no such
> viewer exists. So the 3d world mounting jig solves this issue
for
> those with a relatively tight refractive errors, assuming the
errors are
> equal in each eye, because the viewer focuses both lenses on the
same
> plane. However, those with strong refractive errors, or
mismatch
> refractive errors, or astigmatisms - are forced to wear the
corrective
> eye wear. Combi viewer does focus each eye separately, but it
is very
> sensitive to eye rotation.... as the lenses are ultra sensitive to
eye
> position...if the pupil is the slightest bit off-center axis,
distortion
> is entered into one eye, or both....often setting up binocular
rivalry -
> and usually a headache or dizziness shortly thereafter. Quite
the
> challenge.... But for 35mm film, if your IPD is not less than
say
> 64mm, its the best viewer on the market IMO. They also offer the
45mm
> lenses....but ....
>
>
> Bottom line..... 35mm stereo photography has just a few advantages
over
> MF. Currently, the line of RBT cameras allow for interchangeable
lens
> fl's, a nice benefit. For the same composure / same DOF, you
will gain
> 2 stops of shutter speed, sometimes this is mandatory. The gear
is
> MUCH smaller and lighter. Film is cheaper. A ton of viewers
are
> available off -the-shelf. Other than these issues, i can't think
of
> any other advantages of 35mm stereo. Well, maybe more people use
it,
> so you can share views with more people.... But for max. WOW
factor,
> MF is clearly the winner.
>
> Hope this helps!
>