| DVD Roundup November 2005
All About Aspect Ratios --
Part Three
 By buying a widescreen video
display, many people thought they would eliminate the annoying black bars that accompanied
the home viewing of any film not shot in the 4:3 aspect ratio. Boy, were they
surprised. If you have $30,000-plus to spend on a video projection system and another pile
of money to furnish the room with a variable-mask screen, you can have cinema-like movie
presentations at home. But until there are more reasonably priced flexible video displays
that can screen films the way they’re shown in movie theaters, the problem of black
bars will remain, and the rest of us will have to deal with what we can afford.
Not too many years ago, the 16:9 aspect ratio was "the
next big thing" because it was the format selected for high-definition television.
And, at first glance, it looks as if 16:9 (or 1.78:1) would be a perfect fit for films.
But would you be surprised to know that it’s possible that no movie has ever
been shot in the 1.78:1 format? So why was this ratio chosen for HDTV when they could have
selected just about any aspect ratio?
An analysis was done of all programming that might be
viewed on an HDTV monitor, and 1.78:1 was selected because it resulted in the smallest
range and magnitude of "screen-fit" problems. Of course, this didn’t mean no
screen-fit problems -- an unattainable goal with a video display of fixed size.
Films with a 1.66:1 aspect ratio are transferred to fit the
width of the 1.78:1 widescreen monitor by removing just a few lines at the top and bottom
of each frame. 1.85:1 movies can fit a 1.78:1 video monitor and leave only very thin black
bars at the top and bottom of the screen. Widescreen movies shot in 2.35:1 will have more
obvious black bars at the top and bottom of a 16:9 screen.
What to do about the vintage format, 1.33:1 (4:3)? If you
want to see the entire, undistorted 4:3 frame on a 1.78:1 display, there’s no way to
escape black bars on the left and right sides of the image. Display technologies with
pixels that "age" and grow weaker with use (plasma and CRT) now make the unused
areas gray so that pixels in the unused area will age at the same rate as the pixels that
are always creating images.
Electronics to the rescue! Not.
TV manufacturers know how much a certain segment of the
public hates to see black bars anywhere near their video images, so to some displays they
add zoom, stretch, and nonlinear stretch modes. Zoom mode removes black bars at the top
and bottom of the image by zooming in until the image fills the screen from top to bottom
and from left to right. But what about the parts of the frame that are lost when you zoom
in? You won’t see things the director may have wanted you to see.
Stretch mode makes a 4:3 image fill the screen by
stretching it, making people look short and fat. Wheels aren’t round, and neither are
heads. It’s distracting.
Nonlinear stretch modes do something similar, but stretch
the center of the image very little while stretching the edge areas much more. This mode
is supposed to be less distracting than normal stretch mode, but I find it horrid to watch
-- I tire quickly of people with egg-shaped heads. Just because you can do something
doesn’t mean you should.
Widescreen on optical discs
Widescreen DVDs have been with us long enough that people
tend to forget that the DVD was originally developed as a 4:3 format, aka
"fullscreen." Widescreen DVD came a little later, when the big brains behind the
DVD format realized they could add back the strips of image for the left and right sides
of the movie. Three separate segments of image data are joined into complete widescreen
frames on the fly -- miraculously and without visible glitches. Widescreen DVDs are really
a kludge, but one that works quite well and is infinitely better than early letterboxed
DVDs.
HD-DVD and Blu-ray, the two competing hi-def optical disc
formats, will both begin as 1.78:1 widescreen formats. They will be introduced in the US
in late 2005, with wider availability of players and titles in 2006.
The new face of movie composition
Conventional 35mm film frames retain a 4:3 aspect ratio
because of the space taken up by the conventional analog soundtrack. To get a widescreen
movie to fit in the 4:3 aspect ratio of conventional film stock, movies are frequently
shot with Panavision cameras and lenses, which squeeze the images horizontally, making
everything look skinny and tall. When shown in theaters, the images are unsqueezed with a
special projector lens to restore the widescreen aspect ratio. These squeezed images are
called anamorphic.
 The new(er) kid on the block, Super35 film,
first appeared around 1985. It uses a digital soundtrack that takes up much less space
than the analog variety, leaving enough room for a 1.60:1 frame. Super35 is growing
increasingly popular with the increasing use of computer graphics, which are difficult to
create with the correct anamorphic appearance to match live-action Panavision footage.
Super35 doesn’t employ the Panavision lenses and cameras used to create anamorphic
images on standard 35mm stock.
Super35’s 1.60:1 frame allows the cinematographer to
compose for two or three aspect ratios simultaneously, using different sets of reference
marks in the camera’s viewfinder. One set of marks shows the film’s theatrical
aspect ratio, most commonly 1.85:1, 2.10:1, or 2.35:1. Other sets of marks can show
home-video frame sizes: 1.78:1 and/or 4:3. Seeing two or three sets of reference marks
simultaneously allows the cinematographer to compose for all three, thus minimizing
aspect-ratio problems when the film is transferring to one of those ratios. This means
that the transfer to video formats often results in no black bars for fullscreen or
widescreen fans to deal with. Extremely wide aspect ratios can still be transferred to
widescreen optical disc with black bars at the top and bottom to preserve the full
theatrical aspect ratio, if that is the preference of the director, cinematographer, and
studio.
This installment concludes this series of articles on
aspect ratios in the movies and at home.
…Doug Blackburn
db@hometheatersound.com |
