From: daver@felix.filenet.com (Dave Richards)
Newsgroups: rec.video
Subject: Re: The TRUE Anamorphic Ratio, was Re: Coming out of the closet...
Date: 5 Sep 92 02:43:19 GMT
Reply-To: daver@fritz.filenet.com (Dave Richards)
Distribution: usa
Organization: Costa Mesa, CA

In article <1992Sep02.002044.13125@uhura.neoucom.edu> wlrc@uhura.neoucom.edu (William R. Cruce) writes:
>In article <19834@fritz.filenet.com> daver@fritz.filenet.com (Dave Richards) writes:
>>I hate to make a pest of myself, but the 35mm anamorphic aspect ratio is not
>>2.35:1.  It's 2.39:1 (I round it to 2.4, but most people seem to love the
>>two-decimal-place accuracy.)  It has been 2.39:1 for the last 21 years, or
>>since 1971.  I'll keep bringing this up until people either a) start using
>>the right number, or b) stop quoting ANY specific value and just say "scope"
>>or "anamorphic."
>
>Could you elaborate a bit?  Perhaps the reason people use 2.35:1 is
>because that's what Carr & Hayes use throughout their book WIDE SCREEN
>MOVIES.  The book is full of so many other errors that I'm not going
>to go to battle over this one.  I'd just like to know why you say
>2.39:1 is the correct ratio.

The reason Carr & Hayes use 2.35 is probably because most of the old die-
hards in the film industry use it (incorrectly).  Either that, or they just
don't know any better.  One of the problems with formats is that they become
easy to refer to by the aspect ratio.  Then the aspect ratio is changed for
some reason, and although everybody *knows* the aspect ratio is a new number,
they continue to use the old number because THAT has become the name of the
format.  This happened with the Academy ratio (supposedly 1.333:1 but actual-
ly 1.37:1, and it happened with anamorphic movies.  I don't want to be too
long-winded about the history of the format, but here's a quick summary:

Fox first demonstrated CinemaScope in 1952.  That demo apparently used
the full 35mm (silent) frame, with the sound reproduced from a separate
filmstrip.  When optically unsqueezed, the aspect ratio of the picture
was 2.66:1.  The first feature in "'Scope" was "The Robe", in 1953.
For that release (at least the road-show engagements), four magentic
tracks were added to the film with the picture.  Even though they used
a special film with narrow perforations, the picture width had to be 
reduced to allow room for the tracks.  The aspect ratio became 2.55:1.
But theatres were reluctant to modify their projectors to show 'Scope
films.  So in 1956 they added the standard optical track along with 
the magnetic tracks, again reducing the picture width.  The aspect ratio
became 2.347:1, and remained so for 15 years.  That appears to be the
cause of the famous "2.35" number.

But in 1971, the picture height was reduced to minimize the appearance of
splices on the screen.  Since then it has been 2.394:1.  That was 21 years
ago, but the "2.35" name has stuck.  It really doesn't make any difference
until people start trying to measure the aspect ratio of software.  Then
this business of referring to a film format by it's aspect ratio causes
problems.  Of course, if everybody used the correct number it wouldn't be
a problem.  But it's a fact of life that picture dimensions will keep
changing, for whatever reason.  So it's best to simply call it "Scope",
or "anamorphic 35", and let it go at that.  I should mention that it is
not altogether wrong to use the 2.35 number.  You would be correct in ap-
plying that figure to an anamorphic film made between 1956 and 1971.  
Likewise, the "true" aspect ratio for anamorphic films made between 1953
and 1956 would be 2.55:1, but there weren't too many.

If you would like a reference for the 2.39:1 ratio, try:
	ANSI PH22.195-1984, "Projectable Image Area, 35mm"
	American Cinematographer Manual, 6th ed.

(you may have to calculate the ratio from the dimensions given.)

Dave