posted 05-28-2005 06:31 AM                       

quote: Joshua Waaland

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Why would they devise a new aspect ratio, make it the standard for all new tv's, and have it be something that doesn't coincide with the scope lens aspect ratio?

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posted 05-28-2005 05:45 PM                       

I recall reading somewhere that a major consideration was that television design engineers figured out early on that 1.77:1 was the widest aspect ratio that conventional CRTs [glass picture tubes] could achieve and still be mass-producible and acceptable to consumers. Something to do with laws of physics and how streams of electrons are controlled within the glass envelope, and if you had a scope-ratio screen the neck of the tube for a 30-something inch set would be too deep to fit through a door. I'm googling it but so far I can't find anything though. Maybe someone else knows. Maybe I imagined reading this while in a drunken stupor.

EDIT: I found this on www.tvtechnology.com (nothing mentioned about my CRT theory though):

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16:9 is close to the linear (1.76:1) and geometric (1.75:1) means of the world's most popular theatrical projection aspect ratios (1.66:1 and 1.85:1). It's close to a Motion Picture Association-proposed 1.5x anamorphic projection system (1.76:1). It nicely matches a three-perforation length frame of 35mm film. It's close to an old 1.75:1 projection standard. It allows a large 4:3 image to be displayed with three smaller ones stacked next to it. It works with digital component sampling rates and color sub-sampling. It allows square-sampled HDTV with 1920 active pixels per line to fit in common memory sizes. It allows dual-aspect-ratio memory readouts at 4fsc and 3fsc sampling rates. It's 4:3 x 4/3 (and another 4/3 factor brings it up to CinemaScope).

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posted 05-28-2005 08:26 PM                       

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It allows a large 4:3 image to be displayed with three smaller ones stacked next to it.

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posted 05-31-2005 08:28 PM                       

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Why would they devise a new aspect ratio, make it the standard for all new tv's, and have it be something that doesn't coincide with the scope lens aspect ratio?

Dunno, but my best guess here is that scope size TVs would actually be too expensive and I don't see a scope type aspect ratio ever coming into use for regular TV.

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posted 06-03-2005 02:57 PM                       

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After that, they tackled the second most basic of issues, the shape of the pictures.

This much they knew: Cinemat-ographers sometimes shoot for a 4:3 TV screen. They sometimes shoot for a roughly 2.4:1 CinemaScope-shaped theatrical screen (at the time it was called 2.35:1). They sometimes shoot for shapes in between. Only in extraordinary circumstances do they shoot for any wider or narrower shapes.

The E of SMPTE stands for engineers. So the engineers tackled an engineering problem. What is the shape that will have minimum area loss for any shape between 4:3 and 2.35:1? The answer is roughly 1.77:1, pretty close to 16:9.

Like it so far? There's more. 16:9 is close to the linear (1.76:1) and geometric (1.75:1) means of the world's most popular theatrical projection aspect ratios (1.66:1 and 1.85:1). It's close to a Motion Picture Association-proposed 1.5x anamorphic projection system (1.76:1). It nicely matches a three-perforation length frame of 35mm film. It's close to an old 1.75:1 projection standard. It allows a large 4:3 image to be displayed with three smaller ones stacked next to it. It works with digital component sampling rates and color sub-sampling. It allows square-sampled HDTV with 1920 active pixels per line to fit in common memory sizes. It allows dual-aspect-ratio memory readouts at 4fsc and 3fsc sampling rates. It's 4:3 x 4/3 (and another 4/3 factor brings it up to CinemaScope). Methinks I could go on, but this paragraph is already too long.

NOT SO FAST

With so much going for 16:9, the engineers of SMPTE's WG-HDEP voted unanimously in favor of it the very first time it was brought up. They were probably very pleased that they had solved their little engineering problem. And, with SMPTE's approval, 16:9 spread worldwide.

There's not much that everyone agrees on in television. Frame rate? Hah! The infamous Table 3 of ATSC standard A/53 lists six of them. Number of active lines in HDTV? There are at least 1080 and 720 (with some folks also buying 810, 576, 540, and even 480 under certain circumstances). Colorimetry? Surely you jest. Rec. 709? Rec. 601?

The one and only thing that everyone in the world agrees on for HDTV is that it has a 16:9 aspect ratio. After all, SMPTE's WG-HDEP solved that little engineering challenge back in 1984.

There's just one little problem with the little solution to that little engineering challenge. It wasn't an engineering challenge in the first place.

Yes, 16:9 is close to the ideal shape for minimum area loss for all aspect ratios between 4:3 and 2.35:1. So? Who cares about minimum area loss?

If cinematographers were concerned about saving film stock, they could have switched to three-perforation 35mm film frames long ago. Instead, if they haven't been using anamorphic lenses on 4:3 frames, they've been shooting on roughly 4:3 film frames and using horizontal viewfinder lines to determine what'll be seen in various display aspect ratios. That way, each display has the same left and right edges, and characters enter and leave the frame at the same time regardless of aspect ratio. And, anyhow, even the SMPTE WG-HDEP engineers intended the 16:9 shape only for shooting, not for display.

Kerns Powers, who introduced 16:9 to the SMPTE working group, acknowledged the error in an NAB presentation 10 years later. "Had the SMPTE working group been aware in 1984 of the full-frame (soft mat) protection scheme, it is by no means obvious that 16x9 would have amassed the advantages over 4x3 that persuaded the working group to make that choice." Oops.

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SMPTE recognizes Dr. Kerns Powers for his contributions to electronic cinematography, including important work in progressive scanning and the engineering basis for the 16:9 aspect ratio. Dr. Powers has been active in the broadcast industry for over 50 years, and has been instrumental in key developments in the work of SMPTE. He held technical and management positions with RCA/Sarnoff Laboratories beginning in 1951. As Director of
Communications Research, in addition to directing RCA's Communications Research program, he had responsibility for supporting RCA's Broadcast Equipment and Cable TV businesses. Prior to his retirement in 1987 Dr. Powers was Staff Vice President of Communications Research, which included responsibility for three Laboratories, including the Advanced Video Systems Research Laboratory. His contributions to the communications industry were at the highest level, including work which led to important SMPTE standards. His research while at RCA included work on ELF communications systems, satellite communications, and studies of cellular array mobile communications systems, ballistic missile technology, speech synthesis, and other applied and pure research projects. He holds BSEE and MSEE degrees from the University of Texas and an Sc.D. degree from MIT. Dr. Kerns Powers holds SMPTE's highest level of membership, and received the Progress Medal in 1988, and is a Fellow of the IEEE.

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The Father Of 16:9
The most prevalent aspect ratios filmmakers deal with today are: 1.33 (The Academy standard aspect ratio),
1.67 (The European widescreen aspect ratio), 1.85 (The American widescreen aspect ratio), 2.20
(Panavision), and 2.35 (CinemaScope). Attentive videophiles may note that 1.77 (16:9) isn't on this list and
may ask: "If 16:9 isn't a film format, then just exactly where did this ratio come from". The answer to this
question is: "Kerns Powers".
The story begins in the early 1980s when the issue of high definition video as a replacement for film in movie
theaters first began to arise. During this time, the Society Of Motion Picture And Television Engineers
(SMPTE) formed a committee, the Working Group On High-Definition Electronic Production, to look into
standards for this emerging technology. Kerns H. Powers was then research manager for the Television
Communications Division at the David Sarnoff Research Center. As a prominent member of the television
industry, he was asked to join the working group, and immediately became embroiled in the issue of aspect
ratios and HDTV. The problem was simple to define. The film community for decades has been used to the
flexibility of many aspect ratios, but the television community had just one. Obviously a compromise was
needed.

As the story goes, using a pencil and a piece of paper, Powers drew the rectangles of all the popular film
aspect ratios (each normalized for equal area) and dropped them on top of each other. When he finished, he
discovered an amazing thing. Not only did all the rectangles fall within a 1.77 shape, the edges of all the
rectangles also fell outside an inner rectangle which also had a 1.77 shape. Powers realized that he had the
makings of a "Shoot and Protect" scheme that with the proper masks would permit motion pictures to be
released in any aspect ratio. In 1984, this concept was unanimously accepted by the SMPTE working group
and soon became the standard for HDTV production worldwide.
Ironically, it should be noted, the High-Definition Electronic Production Committee wasn't looking for a display
aspect ratio for HDTV monitors, but that's what the 16:9 ratio is used for today. "It was about the electronic
production of movies," Kerns Powers states, "that's where the emphasis was". Interestingly, today, there is
little talk today about the extinction of film as a motion picture technology, but there is a lot of talk about
delivering HDTV into the home. And, as a testament to Kern H. Powers clever solution, it's all going to be on
monitors with a 16:9 aspect ratio.

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