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Aspect Ratios!!!!!!!


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#1 Bugs Haller

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Posted 16 December 2009 - 12:52 AM

Why is it that no two documents in the English speaking world give you the same information as it pertains to aspect ratios?

Why is it that the math works out to 2.39 but everyone calls it 2.40... and don't get me started on 2.35...

Actually here are my questions:

In the 9th edition of the ASC manual on page 34 it says:

"The most salient advantage (anamorphic over 1.85) is the much larger negative area. A 55% increase in negative area over 1.85 results in finer grain, better opticals, and an increase in apparent sharpness (I say apparent because while a similar image photographed in 1.85 will be sharper, the increase in grain and greater magnification actually make it appear less sharp).

Greater magnification? I must be missing something. Why would 1.85 require magnification. I thought you did a contact print with 1.85 and then used a 1.85 projector aperture in the theater. Why would this require magnification?

Next question:

Are the actual negative areas as follows...

16 mm = 1.33
35 mm = 1.37
Super 35 mm = 1.33

In the ASC manual at the bottom of page 26 (9th Edition) it says that if you calculate the aspect ratio of Academy Aperture from SMPTE specs the math comes out to 1.37:1 but everyone refers to it as 1.33:1!!!!!!!! And almost never is the ratio called 1:37???

See what I'm talking about? So with that being said how do you say "Full" or "Silent" Aperture and how do you say "Academy"????? Based on what that says then you would refer to both of them as 1.33:1... and that can't be right!

Next Question:

Does Techniscope take an anamorphic print? If it does, why? I know it's 2 perf and you have to print it to 4 perf to project it...

Last question:

Is Imax 1.33:1 or 1.43:1... I've read it as both. What is correct?

Thanks
BH
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#2 David Mullen ASC

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Posted 16 December 2009 - 02:05 AM

In regards to magnification, they are assuming that the 1.85 print and the 2.39 scope print will be shown on the same height screen, with the 2.39 image being wider. Therefore the 1.85 area on the 35mm print has to be enlarged more by the projector lens to fill the same screen height as the scope print does. The 1.85 projector aperture is 11.33mm tall, versus the 17.53mm height of the scope projection aperture.

As for saying 2.40 instead of 2.39, that's just rounding up the number.

If you want to be precise, the scope projection aperture is 20.96mm x 17.53mm, which is 1 : 1.1956645. With a 2X optical expansion horizontally, that's 1 : 2.391329. But who wants to type that out each time? Besides, screen masking (curtains), screen shape, and projector spill will further change the shape of the image.

As for the aspect ratios of formats, there are ANSI guidelines, but keep in mind that camera apertures are often larger than projector apertures.

The 4-perf 35mm Full Aperture is 24.84mm x 18.67mm, which is 1 : 1.33. The Silent Era projection aperture would have been also 1 : 1.33 but slightly smaller overall than Full Aperture probably (remember that you can have the same aspect ratio but not necessarily the same physical dimensions).

4-perf 35mm Academy Aperture is really a sound era projection aperture, though some 35mm cameras had Academy Aperture gates installed, the rest just kept the Full Aperture gates but recentered the lens optically for Academy projection, which has an offset picture because of the soundtrack area on the left side of the print. Think of the Academy rectangle as being smaller and lying inside the larger Full Aperture rectangle, and offset to the right.

The 4-perf 35mm Academy Aperture projection gate is 20.96mm x 15.29mm (1 : 1.37). However, it is not uncommon for people to refer to both the Silent Era Full Aperture and the Sound Era Academy Aperture as 4x3 or 1 : 1.33.

The 15-perf 65mm IMAX negative is 70.41mm x 52.63mm (1 : 1.3378301 if you do the math...) However, projector apertures and screen dimensions vary and the final projected shape is sometimes more like 1.45 : 1.

2-perf Techniscope is only a shooting format; it has to be converted to a 4-perf 35mm anamorphic negative for making scope prints.
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#3 Bugs Haller

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Posted 16 December 2009 - 05:35 PM

In regards to magnification, they are assuming that the 1.85 print and the 2.39 scope print will be shown on the same height screen, with the 2.39 image being wider. Therefore the 1.85 area on the 35mm print has to be enlarged more by the projector lens to fill the same screen height as the scope print does. The 1.85 projector aperture is 11.33mm tall, versus the 17.53mm height of the scope projection aperture.

As for saying 2.40 instead of 2.39, that's just rounding up the number.

If you want to be precise, the scope projection aperture is 20.96mm x 17.53mm, which is 1 : 1.1956645. With a 2X optical expansion horizontally, that's 1 : 2.391329. But who wants to type that out each time? Besides, screen masking (curtains), screen shape, and projector spill will further change the shape of the image.

As for the aspect ratios of formats, there are ANSI guidelines, but keep in mind that camera apertures are often larger than projector apertures.

The 4-perf 35mm Full Aperture is 24.84mm x 18.67mm, which is 1 : 1.33. The Silent Era projection aperture would have been also 1 : 1.33 but slightly smaller overall than Full Aperture probably (remember that you can have the same aspect ratio but not necessarily the same physical dimensions).

4-perf 35mm Academy Aperture is really a sound era projection aperture, though some 35mm cameras had Academy Aperture gates installed, the rest just kept the Full Aperture gates but recentered the lens optically for Academy projection, which has an offset picture because of the soundtrack area on the left side of the print. Think of the Academy rectangle as being smaller and lying inside the larger Full Aperture rectangle, and offset to the right.

The 4-perf 35mm Academy Aperture projection gate is 20.96mm x 15.29mm (1 : 1.37). However, it is not uncommon for people to refer to both the Silent Era Full Aperture and the Sound Era Academy Aperture as 4x3 or 1 : 1.33.

The 15-perf 65mm IMAX negative is 70.41mm x 52.63mm (1 : 1.3378301 if you do the math...) However, projector apertures and screen dimensions vary and the final projected shape is sometimes more like 1.45 : 1.

2-perf Techniscope is only a shooting format; it has to be converted to a 4-perf 35mm anamorphic negative for making scope prints.


Thank you David! I was hoping you would respond to this.

I just want to make sure I understand you correctly:

1.37 is really a "projection aperture"?

And if the camera apertures are bigger than the projector apertures... then that would mean you would lose a little of your image in projection, correct? Although I guess you would never project 35 mm as 1.33 anyway...

Thank you for your responses...
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#4 David Mullen ASC

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Posted 16 December 2009 - 06:13 PM

Thank you David! I was hoping you would respond to this.

I just want to make sure I understand you correctly:

1.37 is really a "projection aperture"?

And if the camera apertures are bigger than the projector apertures... then that would mean you would lose a little of your image in projection, correct? Although I guess you would never project 35 mm as 1.33 anyway...

Thank you for your responses...


The Academy Aperture was invented in 1932 as a projection aperture. Previously, you had the Movietone Aperture, where the side of the print was trimmed by the optical soundtrack, reducing 1.33 in width to around 1.20. This was deemed as too square in shape, so the tech branch of AMPAS recommended the height of the projector gate be shortened to compensate. I guess they settled for 1.37 as the final shape because the movie palaces back then had such a high raking angle for the projector, due to the balcony seats, that keystoning of the projected image sort of shortened part of the rectangle, so they made it a 1.37 gate instead of a 1.33 gate.

Anyway, that's one theory.

You don't necessarily "lose" your image if you composed it with the projection area in mind, hence why we use groundglass markings.

Because of hairs in the gate, etc. it's always a good idea for the camera aperture to be larger than the projection aperture.
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#5 Shaan Aslam

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Posted 24 January 2010 - 03:12 AM

Keeping with the discussion of aspect ratios, I recently came across a discussion of Abel Grance's film Napoleon. Apparently, Grance intended Napoleon to be projected using "Polyvision", an extreme wide-screen format with an aspect ration of, (get ready!)...4.00:1. It is supposed to be three 35mm projectors projecting the film on to a screen, but that sounds oddly familiar to Cinerama which has an aspect ration no where near 4.00:1. Does any one have any insight on this beast of a format?
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#6 Brian Pritchard

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Posted 24 January 2010 - 04:05 AM

Keeping with the discussion of aspect ratios, I recently came across a discussion of Abel Grance's film Napoleon. Apparently, Grance intended Napoleon to be projected using "Polyvision", an extreme wide-screen format with an aspect ration of, (get ready!)...4.00:1. It is supposed to be three 35mm projectors projecting the film on to a screen, but that sounds oddly familiar to Cinerama which has an aspect ration no where near 4.00:1. Does any one have any insight on this beast of a format?


The final reel of 'Napoleon' is designed to be shown as a triptych using three projectors so you get 3 x 1.33 (the silent format) giving 4.00:1. The remaining reels are normal silent aperture. It has been shown in London at the BFI using three projectors and elsewhere I believe.

Many archives still show silent films using the 1.33; 1 aspect ratio.

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#7 David Mullen ASC

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Posted 24 January 2010 - 04:30 AM

Keeping with the discussion of aspect ratios, I recently came across a discussion of Abel Grance's film Napoleon. Apparently, Grance intended Napoleon to be projected using "Polyvision", an extreme wide-screen format with an aspect ration of, (get ready!)...4.00:1. It is supposed to be three 35mm projectors projecting the film on to a screen, but that sounds oddly familiar to Cinerama which has an aspect ration no where near 4.00:1. Does any one have any insight on this beast of a format?


Three 1.33 4-perf 35mm images gets you 3.99 : 1.

The Cinerama format used three 6-perf 35mm frames about 0.88 : 1 each for 2.66 : 1 total.
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#8 Brian Pritchard

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Posted 24 January 2010 - 05:25 AM

Three 1.33 4-perf 35mm images gets you 3.99 : 1.

The Cinerama format used three 6-perf 35mm frames about 0.88 : 1 each for 2.66 : 1 total.

Actually if you want to be pedantic the SMPE 1922 Standards give the projection aperture as 0.748" by 1.109" which gives an aspect ration of 1.333333 reoccurring - 1.333333 x 3 = 3.999999 which as far as I am concerned is 4.0 to 1.

Some other facts that come from these standards are that the camera cranking speed was set at 60 ft per minute and the projection speed at 80 ft per minute. It also states that any new formats should retain the 4:3 aspect ratio - nobody listened to that!
The 1922 standard was the point where the primary measurement for '35mm' film was changed from 1 3/8 inches (34.95mm) to 35mm.
If you are interested in these standards you will find them at http://www.brianprit...E_Standards.htm
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#9 Shaan Aslam

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Posted 24 January 2010 - 06:46 PM

Thank you Brian and David for explaining. I was really confused!
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#10 John Sprung

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Posted 25 January 2010 - 02:42 PM

Actually if you want to be pedantic ....


After thinking it over for a while, yes, I really do kinda like being pedantic sometimes..... ;-)

So, here goes again: There ain't no such thing as 2.40:1. If you do the math on the actual aperture dimensions and squeeze ratio, it's really 2.39:1. Somehow, within the last five years or so, this strange error has been introduced all over the place. Before that, everybody knew it was 2.39 and used 2.39 in writing about it. I know I've pointed this out many times before, probably to the point of being a pain in the tush.





-- J.S.
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