Why original Silent ratio 1.33:1 increased to 1.37:1 in 1`932?

[Peter J Mason]

Does anybody know the reason why the original Silent ratio of 1.33:1 was increased to 1.37:1

when the sound Academy Aperture was introduced in 1932?

 

Regards,

Peter Mason

[Simon Wyss]

It wasn't. The difference between the aperture aspect ratios stems from the several steps the AMPAS standard went through. The silent (today so-called full) aperture has been agreed upon at a Paris international congress in 1909 and was 18 on 24 millimeters or .709 by .945 inches.

 

When one cut off a tenth of the width inside the perforation for the sound track it wasn't so clear what the height should be. One settled at .631 by .868 in. which later became altered to 630 by 867. European standards provided for a 3 mm high frameline.

 

The screens were three to four all of the time, and are still today for everybody who uses that dynamic format. As ISO 2907 reads: It is recognized that, in many cases, the actual film image area that is projected may be smaller than the maximum projectable image area. It is intended that the actual projected image area be the largest appropriately shaped figure that can be inscribed within the specified dimension.

[David Mullen ASC]

It's still a valid question, because the Academy Aperture dimensions are 1.37 : 1 for some reason. Some people say that it was some minor correction for the keystoning due to the extreme projection angles that movie palaces were using (like Radio City Music Hall), that the slight wider ration helped keep the picture from looking as skinny. Don't know if that's true. It may have been a desire for a wider aspect ratio, though minor.

 

The Wikipedia entry:

http://en.wikipedia.org/wiki/Academy_ratio

 

... implies that SMPE set a standard of .800 x .600" and then AMPAS changed the width to .825", maybe feeling that .800 was unnecessary to make enough room for the optical track, but they didn't change the vertical.

[John Sprung]

Some people say that it was some minor correction for the keystoning due to the extreme projection angles that movie palaces were using ....

 

More likely it just wasn't that big a deal. The change is only 3%, which is less than the amount you have to file the aperture for keystone in many cases.

 

 

 

 

-- J.S.

[Michael Collier]

That is interesting John, I know little about projection tech. Are you saying that to this day they will file the gate to compensate for keystone? I always assumed it was an optical correction in the lens (like a swing shift with some kind of focus compensation).

[Hal Smith]

Not only do professional film handlers file their gates for vertical keystoning, the really thorough ones file gates for the slight difference in horizontal keystoning when running side by side changeover projectors running film off reels (not single projectors with platters like the multiplexes). And like all professionals, they argue among themselves as to who makes the best aperture files.

[John Sprung]

Are you saying that to this day they will file the gate to compensate for keystone?

 

Yes, I did it myself in 1997 when we moved a pair of AA-2 Norelco's from the Four Star to the Grand in San Pedro. The old house was just a couple degrees down, the Grand is 14 degrees. I learned a few things about projection back when I was sharing rooms with the Paramount projection staff.

 

 

 

 

 

-- J.S.

[Peter J Mason]

Yes, I did it myself in 1997 when we moved a pair of AA-2 Norelco's from the Four Star to the Grand in San Pedro. The old house was just a couple degrees down, the Grand is 14 degrees. I learned a few things about projection back when I was sharing rooms with the Paramount projection staff.

 

 

 

 

 

-- J.S.

 

 

According to information in the British Kinematography Journal of July 1956(page 20) the 1.37:1 ratio was chosen

to compensate for an average projection angle of 14 degrees. This means that a 1.37:1 ratio projected

downwards at 14 degrees will give a projected image of 1.33:1 ratio.

 

This information was stated as coming from a SMPTE booklet .

So exactly the same projection angle as the GRAND mentioned by John Sprung above.

Is there anybody out there who can do the math?

[John Sprung]

A down angle doesn't change the aspect ratio, it changes the shape of the image. The top of the screen is closer to the projector than the bottom, so the top of the picture is smaller than the bottom. A rectangle on the film becomes a trapezoid on the screen. So, you file the aperture into a trapezoid to make it come out rectangular on the screen.

 

I don't remember the exact screen height we had, guessing about 25 feet, but the throw was 120 feet. Roughing it out in AutoCad, the bottom should be about 5% wider than the top. So, you're only dusting a couple thousandths off each side to square it up.

 

 

 

 

-- J.S.

[Brian Pritchard]

There was a lot of discussion in 1930 in the SMPE Journals regarding projection aperture. There was an article in Jan 1930 by Lloyd Jones of Kodak entitled 'Rectangle Proportion in Composition'. The SMPE maintained that the aperture should be kept at 1.33 for sound on film prints. There is further information that says that many major studios in Hollywood used different projection apertures in their theatres. Later, in May 1930, the SMPE issued the following statement:

 

"WHEREAS, Investigation has revealed wide variance in

theater projection practices and that there is no effective

standard aperture for projection of sound-on-film talking

motion pictures;

"Be it resolved: That as a temporary measure this committee

recommends that all studios and cinematographers

using sound-on-film methods make marks on the camera

ground glass equally spaced from the top and bottom in

addition to the mat mark for the sound track ; these marks

to delineate a rectangle 0.620 by 0.835 inch in size and that

all vital portions of the picture be composed within these

limits;

 

This gives a ratio of 1.35.

 

In Feb 1932 the Standards Committee recommended an aperture of 0.590 x 0.825, a ratio of 1.4.

 

In March 1932 the Standards Committee settled on an aperture size of 0.825 x 0.600 giving a ratio of 1.37. This was after a simultaneous study with the Academy of Motion Picture Arts and Sciences. There is no mention as to why they had finally settled on this size.

 

Brian

[Russell Richard Fowler]

You also had two competing sound systems....Vitaphone = Disc = silent aperture and Movietone = Optical sound with a "square" aperture due to the space given up for the soundtrack. To show both types of sound playback required shifting of projectors and /or use of a moveable mask to cover the screen between formats...by the early 1930's disk was losing out to optical sound so a 1:37/1 ratio simplified presentation.

There are lens P.C. adapters to eliminate keystone ( and some projector lens turrets are able ) but I had to remove some out of a couple of locations and go back to custom filed aperture plates since the projectionists could not understand why the projectors where not "pointing" to the screen....because of the optical shift.

[Dominic Case]

A down angle doesn't change the aspect ratio, it changes the shape of the image. The top of the screen is closer to the projector than the bottom, so the top of the picture is smaller than the bottom. A rectangle on the film becomes a trapezoid on the screen. So, you file the aperture into a trapezoid to make it come out rectangular on the screen.

 

Hmm. I agree completely that the rectangle becomes a trapezoid, so you file the gate out to compensate. (Which, by the way, means that the framing is inevitably slightly different from what the cinematographer intended: vertical lines near the side of the frame give the game away very quickly, 'cos they are no longer vertical).

 

But I think that the down angle would also change the aspect ratio. As the screen is not at right angles to the projected beam of light, the vertical dimension of the beam is increased, while the horizontal stays the same. (I found it easier to visualise a round beam of light (as in a spotlight) projected onto a square-on surface producing a circle of light: then, on tilting the surface, you get an ellipsoid (or some kind of oval anyway).

 

So a tilted projector would produce more height for the same width: a 1.37:1 projector mask would therefore produce a 1.33:1 image on the screen.

 

Of course that is measuring across the middle of the frame. What is the aspect ratio of a trapezoid ? :blink: :unsure: Filing the mask out will alter the aspect ratio in a much more tangible way.

[John Sprung]

Exactly -- a trapezoid doesn't *have* an aspect ratio. The term is only defined for rectangles.

 

But when you file the sides to get back to a rectangle, you get a new ratio. That's something I'll have to mess with in AutoCad again when I get the time....

 

 

 

 

-- J.S.

[Russell Richard Fowler]

The Schneider Optical Theatre Design Program for Cinema lenses display keystone image information on a flat or curved screen based on the elevation of projector lens ( e.g. tilt angle ) to the center of the projection screen. It also gives information on how much a given lens can be optically shifted to lessen keystone. I have a location that is used for Film festivals in Miami in which the projectors are at 14 degree tilt.......with the top edge of the image versus the bottom having an 18 inch difference in width....which the aperture plate "squares up"........no luck with subtitled prints which exhibit the keystoning on the letters.

[Peter J Mason]

There was a lot of discussion in 1930 in the SMPE Journals regarding projection aperture. There was an article in Jan 1930 by Lloyd Jones of Kodak entitled 'Rectangle Proportion in Composition'. The SMPE maintained that the aperture should be kept at 1.33 for sound on film prints. There is further information that says that many major studios in Hollywood used different projection apertures in their theatres. Later, in May 1930, the SMPE issued the following statement:

 

"WHEREAS, Investigation has revealed wide variance in

theater projection practices and that there is no effective

standard aperture for projection of sound-on-film talking

motion pictures;

"Be it resolved: That as a temporary measure this committee

recommends that all studios and cinematographers

using sound-on-film methods make marks on the camera

ground glass equally spaced from the top and bottom in

addition to the mat mark for the sound track ; these marks

to delineate a rectangle 0.620 by 0.835 inch in size and that

all vital portions of the picture be composed within these

limits;

 

This gives a ratio of 1.35.

 

In Feb 1932 the Standards Committee recommended an aperture of 0.590 x 0.825, a ratio of 1.4.

 

In March 1932 the Standards Committee settled on an aperture size of 0.825 x 0.600 giving a ratio of 1.37. This was after a simultaneous study with the Academy of Motion Picture Arts and Sciences. There is no mention as to why they had finally settled on this size.

 

Brian

 

Apparently there was an AMPAS bulletin released on 25 March 1932 regarding the new aspect ratio.

Does anybody have access to this?

[Dominic Case]

Apparently there was an AMPAS bulletin released on 25 March 1932 regarding the new aspect ratio.

Does anybody have access to this?

No, but I do have the AMPAS annual report for 1929, which also quotes the "WHEREAS . . . . . be it resolved . . . etc" statement. There is an additional paragraph to this statement which Brian didn't quote that is interesting in the light of more recent discussion in this thread. It says:

 

BE IT ALSO RESOLVED: That the committee further recommends that theatres which make a practice of reestablishing the full screen proportions from sound-on-film pictures do so by the use of an aperture whose size would be 0.600 by 0.835 inches

on the basis of projection on the level

, the horizonal center of the aperture coinciding with the horizontal center of the S. M. P. E. Standard Aperture.

my italics - if I read this correctly, it's an attempt to cover the trigonometrically challenging problems of keystoning.

 

Incidentally, this statement was issued by a committee consisting of representatives of no less than four organisations: American Society of Cinematographers; American Projection Society (Chapter 7); SMPTE (Pacific Coast section); and AMPAS Technicians' Branch. The Association of Motion Picture Producers Technical Bureau was also there. What a bunch of organisations, it's a surprise they ever got any work done!

 

BTW another little question. In copying this out I carefully transcribed the exact US spelling of 'center' , but noted that the word 'theatre' is spelt in the English way. It seems to be common in all my American papers from that time, though not so now. Anyone cast any light on how Noah Webster came to be so ignored in the theatrical or cinema business?

[K Borowski]

"Theatre" is more sophisticated, I guess, more old world, whereas American English, in general, is more streamlined and phonetic.

 

The -re came spelling came from French anyway, correct?

 

 

I spell theatre with an -re as do many chains, but then again, I spell grey with an "e" instead of an "a." I know that "African Grey" is always spelled with an "e" here, but, for the most part, the standard American spellings are followed.

 

I've seen "centre" used on shopping centers, again, probably owing to a perception of old-world establishment or sophistication, just as talking with a fake British accent here entails the same thing.