Re: [photo-3d] Camera Coupling - Digital

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

----- Original Message -----
From: "Brian Reynolds" <reynolds@xxxxxxxxx>
To: <photo-3d@xxxxxxxxxxxxxxx>
Sent: Friday, April 06, 2001 9:59 PM
Subject: Re: [photo-3d] Camera Coupling - Digital


> Eric Miner wrote:
> The scanning backs for 4x5 cameras can currently just about match 4x5
> film.

The scanning backs for 4x5 cameras can currently just about match half-frame
35mm film.  The actual image size of the sensing surface (usable area) is
actually quite a bit smaller than 4x5, usually smaller than medium format.
In all fairness, some of the more expensive cameras and backs do exceed 16mm
film.

> > In fact my 8x10s are very impressive too.

I'm sure they are.  Very little resolution is needed for prints, as compared
to transparencies.  Digital cameras are a very good choice if prints are
your only requirement.  I can make very nice 16x20 prints from film
negatives shot with my Tessina subminiature camera. But they don't hold a
candle to same-size prints, let alone transparencies, shot with my MF 120
film camera.

> > Was it Kodak who said that a 35mm motion picture image is less than
> > 50% of a still? I've seen 35mm motion picture film and it looked
> > larger than that to me.
> >
>
> Remember that motion picture film runs through the camera vertically,
> there is more than one 35mm movie film format, and they need to to
> have room for the sound track.  I'm sure John Rupkalvis, or others on
> this list, can cite the actual dimensions of a 35mm movie frame.
>
> --
> Brian Reynolds

There are a LOT of factors to consider when comparing to motion picture
film.

First, remember that an 8x10 print made from a 4x5 negative is only 2x
linear magnification.  A 35mm  motion picture is usually magified over 300
times linearly on the typical movie screen.

Most films shot today are composed and shot in the 1.85:1 aspect ratio.  The
camera image on the film for many years has been a maximum width of .864"
(to allow for the sound track).  This was further reduced in the viewfinder
and projection apertures to .825" (approx. 21mm), with the height being only
.446" (approx. 11mm).

More recently, digital sound tracks (yes, DIGITAL!), on the outside edge of
the film, and/or between the perfs, and/or on separate CD discs, have made
possible the use of nearly the entire area between the perfs, like in the
old silent days.  This allows a camera aperture up to .980" (approx. 24mm)
wide by .735" (approx. 19mm) high. (Does the 24mm dimension sound familiar?
Your full frame camera aperture for your 35mm still camera measures 24mm x
36mm...) Only, they don't call it "full silent aperture" as they used to.
Now, this ancient format has been phoenixed into the modern "Super 35"
format (exactly same size - so much for hype).   Newer major films
("Titanic" was the first of these) are now in full silen - OOPS - Super 35.

Unfortunately, this is not what you see on the screen.  No one, other than
possibly James Cameron has seen the full camera image (not even the camera
viewfinder "quite makes it").  Even the editor would not see it (he/she
looks at a monitor screen for the NLE).  James would see it, because he is
one of the few who is particular enough to examine the original camera
negative with a loupe on a light box.

Projected, the image is ALWAYS cropped, sometimes even more so.  Unlike the
old days when motorized masks adjusted the shape of the screen to the aspect
ratio on the film, most multiplex screens today use the "one size fits all"
philosophy.  Typical screens today are about 2:1 in aspect ratio.  I say
about, as the exact shape depends on the height of the ceiling, the type of
seating, and most important, the budget.

The reason that most theaters aim for about a 2:1 ratio, is that you lose
about the same film area no matter what is shown.  The sides are cropped off
of 'scope films, and the top and bottom off of "flat" 1.85:1 films. (also,
it conveniently is very close to the 2.06:1 ratio of 5 perf 70mm prints,
which almost nobody shows any more).  So much for the purists who insist on
the same aspect ratio on their DVD's as seen in the theaters.  Lots of luck.

So much for rambling on this non-stereoscopic topic (say that fast).  But,
since so much has been said already, I wanted to set the record straight.

However, it does have stereoscopic relevance.  3-D (stereoscopic) motion
pictures are shot and shown in an amazing variety of formats.  Dual
projector systems (usually seen today only in special venues, such as theme
parks) encompass all of the above, and more.  Single projector systems split
the image either horizontally or vertically (okay, so I am ignoring anaglyph
... yes, I will continue to ignore anaglyph).

Yet, the image size is not as bad for 3-D as it might appear.  Flat 1.85:1
is projected through a projector aperture that measures only .825" x .446"
(about .368 sq. in.) and is further cropped to who-knows-what on the screen.
Over-and-under 3-D has an area of about .980" x .374 (about .367 sq. in.)
FOR EACH EYE-VIEW, or nearly twice the area (about .733 sq. in.) of
comparable flat films (if you keep both eyes open) every time the projection
shutter opens.  Okay, so this is cropped an unknown amount on the screen
also.  But, you still have a lot more area to start out with.

Imax 3-D films have a camera aperture (for EACH eye view) of 2.799" (approx.
71.09mm) x 2.072" (approx. 52.63mm), and the Imax projection apertures are a
minimum of .016" narrower at the sides, and a minimum of .080" less top and
bottom than the camera apertures.  Again, with both eyes open, you see twice
this area per shutter opening.  (Yes, there is a shutter in a rolling loop
projector, but probably not for the reason you think).   Get out your
calculators and tell me how many terapixels you need to equal this
digitally...

JR




 

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/