Re: [photo-3d] transparencies vs. prints

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

What is your meaning of "M F stereo"?  When I first read this, I interpreted
it as meaning medium format.  But, you must mean something else, since
medium format stereo can be viewed as either prints or transparencies
(depending on your choice of film and type of viewer), or even projected.  I
project my 6 x 9 (120 film) transparency pairs using a pair of lantern slide
projectors.   The detail and other attributes are absolutely superb, even on
a very large screen (this film size has a larger area than even Imax
images).

Your resolution observations appear very close to what I have observed.  In
general, all things being equal, transparencies have the potential for being
superior to prints in both resolution and tonal scale.

Someone stated that negative film has a greater tonal range than
transparency film, and this seemingly contradictory statement is correct.
The problem is, that prints made from these negatives have a much narrower
range.  That is why you do not have to be as accurate in exposure with
negative film.  Transparency exposure errors of plus or minus one-half stop
can be easily seen by most people as less than optimum in quality.  With
negative film, the same tolerance occurs only on the underexposure side, but
up to two full stops overexposure can be corrected for in printing with
little image degradation.

This is extremely important for stereoscopic images, as both shadow detail
and highlight detail contribute greatly to the impression of depth.

Color dyes tend to diffuse in paper prints much more than on film base.
Also, transillumination will allow both greater detail (resolution) and
wider tonal scale than reflected illumination, for both black-and-white and
color images.  To get an idea of this, take a transparency, and set it on a
sheet of white paper.  Illuminate it with reflected light.  Compare what you
see with what you see when the same transparency is viewed with the light
source behind (going through it).

For a real interesting test, shoot negative film in your stereo camera.
Have both prints and slides made from the same negative pair.  View the
results in a slide viewer and a print viewer.

JR


----- Original Message -----
From: "Don Lopp" <dlopp@xxxxxxxxxxxxxxx>
To: <photo-3d@xxxxxxxxxxxxxxx>
Sent: Friday, February 02, 2001 5:42 PM
Subject: Re: [photo-3d] transparencies vs. prints


> As reguards to the resolution qualities of prints as compared with slides
we
> ran a test in a photo-physics class at the U of W in 1948 where the class
> looked at resolution charts in the form of contact prints and slides. On
> average , the best we could do was - prints- 7 lines per mm with out
> magnification and 14 lines per mm with magnification. With slides,
depending
> on how much magnification , Kodachrome 10 , we could see up to 48  lines
per
> mm-a few claimed to be able to see 56  lines per mm but these claims were
> not seen by anyone when using a decent microscope. This helps me back my
> prejudice against M F stereo which to me is both a clumsey and akward way
to
> view stereo in my opinion not mentioning the lowering tonal qualities etc.
> DON.
> ----- Original Message -----
> From: "Dan Vint" <dvint@xxxxxxxx>
> To: <photo-3d@xxxxxxxxxxxxxxx>
> Sent: Friday, February 02, 2001 8:50 AM
> Subject: Re: [photo-3d] transparencies vs. prints
>
>
> > >
> > >
> > > >   From: "Ferguson Studio" <larry@xxxxxxxxxxxxxxxxxx>
> > > ...
> > > >On another note, the perception that Transparencies are sharper or
have
> a
> > > >longer tonality scale is a myth.  You must factor in size of the
> original
> > >
> > > You know, we've discussed this in the past privately, and we either
> > > disagree or we are misunderstanding each other.  My experience with
> > > practical photography is as yet limited, especially with prints, so my
> > > feeling on this is based on something more like intuition.
> > >
> > > The way I understand it, compared to prints, slides give you more
tonal
> > > impact, more dynamic range when you actually view them.  The OUTPUT
has
> > > greater range.  When brightly illuminated, the perceived brightest
spot
> is
> >
> > Yes this is the difference between a projected/illumintaed source and a
> > reflective print.
> >
> > > lots and lots brighter than the darkest shadow, and the slide will
show
> > > detail in both these brightest and darkest areas if exposed carefully.
> > > Prints made from negatives do not, cannot give you this very wide
range
> in
> > > tonal output!  They can only reflect light diffusely, and this alone
> will
> > > reduce the perceived range.  Prints also cannot perfectly absorb all
> light
> > > (such as a very dark coal black), but then neither can slides.
> >
> > Take a look at a book on the zone system started with Ansel Adams. Slide
> > film typically is a 3 (usal) to maybe 5 zone range that you have to
> carefully
> > place to get a good slide, I beleive print films are like 5 to 7 in this
> 10
> > point scale. It is easier to get more information in a print film and
work
> > with that so you have a more complete tonal range in the picture. In a
> slide
> > you either blow out the highlights or loose the shadow detail in a
slide.
> >
> > >
> > > Another way I look at it is that the negative generally is never fully
> > > transparent.  Completely unexposed, the negative still has some
density,
> > > which looks to be around 10%.  Exposed to the max, it is fairly
opaque.
> > > But this range on the negative film is less than what the slide will
> show:
> > > from nearly perfectly transparent to quite opaque.  (But here I am
> > > guessing.  Emulsion gurus please correct me!)
> > >
> > > The very widest range of tones (reality) is compressed onto the tonal
> range
> > > of the slide, which will range from transparent (brightest) to fairly
> > > opaque (darkest).
> >
> > But it is how much is compressed into the highlight and the shadow.
Print
> film
> > is more forgiving because you don't have to get the filtration and color
> balance
> > 100% on with color print because you can adjust this in the print
process.
> Take
> > your twined rig and load a roll of print and a roll of slide film and
shot
> > duplicate images of a wide range of lighting situations. Get out of the
> studio
> > and into some high contrast situation. Then look at the details in the
> negative
> > vs the slides and you'll be surprised how much you actually loose.
> >
> > You also mention sharpness, for that you would have to look at the
> combination
> > of negative and the paper surfaced used. Your basic gloss no texture
> surface is
> > the sharpest way to go there. For direct measurement I have no test on
> this one.
> > I suppose you could actaully take one of these lens test patterns that
> would
> > show you the resolving power of your lens as well as the film being
used.
> >
> > ..dan
> >
> >
> > >
> > > Larry, you say:
> > >
> > > >...if you would just use a
> > > >densitometer you would see that the tonal scale of a good
transparency
> is
> > > >about three f/stops whereas the tonality scale of a good BW print is
> about
> > > >seven.
> > >
> > > Quite frankly this goes against everything I can see with my own eyes,
> > > against what I tried to explain above.  I don't know what you mean
with
> > > that statement.
> > >
> > > I do understand that negative emulsions have more _latitude_.  This
does
> > > follow logically with the notion that transparency film has greater
> > > _dynamic range_.  Latitude and dynamic range are opposites.  Latitude
is
> > > ability to capture a broad range of tonality, and dynamic range is the
> > > ability to reproduce the broad range faithfully (i.e. uncompressed).
> > >
> > > Imagine the INPUT tonality as a bell curve of values (like the levels
> > > dialog in Photoshop shows it) that has to fit in a receptacle of a
> certain
> > > width.
> > >
> > > Negative film is a relatively wide receptacle, and it can accomodate
the
> > > bell curve of your values even if the curve falls a bit off center as
> you
> > > put it down in the receptacle (the equivalent of under/over exposing).
> > > That's wide latitude.
> > >
> > > Transparency film is a relatively narrow receptacle, only a smidgen
> wider
> > > than the bell curve of tonality you will set down in it.  If you don't
> get
> > > your bell curve set down just right (i.e. good exposure) then part of
> the
> > > curve will spill over one end of the receptacle and be lost (i.e. loss
> of
> > > detail in an overexposed or underexposed region).
> > >
> > > Perhaps what you mean with "seven stops tonality range" is this width
of
> > > the negative film "receptacle?"  because it is wider, because of the
> > > increased latitude, the film can actually capture detail in a broader
> range
> > > of exposure.
> > >
> > > But when you consider the "output", the negative film is compressing
> this
> > > broader range of tonality onto its own actual, physically more limited
> > > range of density.  Then the final output, the print, shows a
> substantially
> > > compressed range of tonality, from a diffuse white to a muted black.
> > >
> > > What makes the transparency so great for viewing is that the range of
> > > tonality in the scene is not compressed so much.  Exposed well, and
> viewed
> > > with lots of light, the transparency will show the scene much as it
was
> > > originally, with minimal "compression" of the lightest and darkest
> areas.
> > >
> > > (I recently read something closely related to all of this: all other
> things
> > > being equal, that negative films are much better for digital scanning.
> > > This is because scanners do not have such a great dynamic range.  Most
> > > scanners cannot handle the dynamic range of a transparency - it is too
> > > much.  Better to scan a negative, where the tonality is relatively
> > > compressed.)
> > >
> > > >Large 4x5" transparencies are in fact less sharp than small 35mm
> > > >trans and resolve fewer lines on resolution charts but their bigger
> size
> > > >makes them appear sharper because they require less degree of
> enlargement to
> > > >make bigger prints so when you enlarge them they are sharper!
> > >
> > > This sounds wrong, theoretically.  Do you mean that the emulsions in
> larger
> > > formats are not as high resolution (I can't believe that), or that the
> > > optics for larger formats do not create images of as high a
resolution?
> (I
> > > don't believe that, either)  Certainly I am unaware of the practical
> limits
> > > of the larger formats.
> > >
> > > I did just shoot my first session with Medium Format, side by side
with
> a
> > > 35mm twin rig.  The MF transparencies make my 35mm originals look like
> poor
> > > quality dupes!  But more to the point, down around the resolution of
the
> > > grain, the MF transparencies do not look any softer than the 35mm
> > > transparency.
> > >
> > > >By the way, how was the shooting with the twin-rig Hasselblad setup
> with
> > > >Betty?  When are we going to actually see a Boris print stereoview?
> > >
> > > Well, ever since I met you Larry, you have raised the bar for me very
> high
> > > indeed.  So it may take a while yet, before I feel that my stereo
cards
> are
> > > going to be up to snuff (i.e. as good as yours).  You might have to
give
> me
> > > a few more weeks ;-)
> > >
> > > Boris
> > >
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
> >
> >
>
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