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

["Don Lopp" <dlopp@xxxxxxxxxxxxxxx>]

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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