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Aspect Ratio ???'s


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16 replies to this topic

#1 of 17 OFFLINE   Gerald LaFrance

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Posted October 06 2005 - 02:15 PM

Hi, I am a little bit confused about Aspect Ratio (ie Star Wars II has a 2.35:1 aspect ratio and Dracula Superbit has a 1.85:1 Aspect Ratio. The Way I figure if I have the higher Ratio anything under that will fit in the screen but with Black bars??

My question is should I just get a screen that has a aspect Ratio of 2.35:1 and all movies under that will just have Black Bars on it to fit according to there Ratio???

I am Probally goin to get the Sanyo Z4 in couple of months I am just confused about how this all works. I read about this in a few sites from HTF and this is how I figure it works, am I close??

I have 11'x 19' room and plan on putting in a 106" screen but I am NOT sure what ratio I should go with any info greatlly appreciated!!

THNX Gerald Posted Image

Edit I just read this :

Easiest way to explain aspect ratio is to say that it means the ratio between the width of the picture and the height of the picture. Normal TV's aspect ratio is 4:3 (1.33:1), HDTV's aspect ratio is 16:9 (1.85:1) and CinemaScope movies' aspect ratio is 2.35:1.

I believe I should go With the 2.35:1 and anything under that aspect ratio should fit within the 2.35:1 screen correct???
"IF the Facts don't Fit the Theory Change the Facts"    Albert Einstein

#2 of 17 OFFLINE   JeremyErwin

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Posted October 06 2005 - 03:35 PM

Perhaps this avsforum thread will be of some assistance.

The easiest thing to do, of course, is to just use a 16:9 screen (which was what the z4 was designed to do), and let the dvd player do its letterboxing & pillarboxing thing. Or you could search this forum for information about"constant height" or "constant area screens"

#3 of 17 OFFLINE   Gerald LaFrance

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Posted October 06 2005 - 07:53 PM

Hi I did a search and came up with some Informative post about constant area screens, but If I go with a 16:9 screen and I put in a 2.35:1 movie(Star Wars) wouldnt it bleed outside of the Screen cause it would be a wider AR?? Or would it fit inside the 16:9 screen and have bars on the bottom ands top??

From what I read the Sanyo Z3-4 is 16:9 Native does this mean it wont go to a AR of 2.35:1???

I dont mind having the bars but I would have to setup 1st to see for myself. And if needed I would build a constant area thingamajig!! Posted Image
"IF the Facts don't Fit the Theory Change the Facts"    Albert Einstein

#4 of 17 OFFLINE   JeremyErwin

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Posted October 06 2005 - 08:45 PM

Ah. Here it is.

2.35 Constant Height Faq

Note that you'll need a scalar,and an anamorphic lens...

#5 of 17 OFFLINE   Jack Briggs

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Posted October 07 2005 - 04:13 AM

FYI, the 16:9 aspect ratio is 1.78:1, not 1.85:1.

#6 of 17 OFFLINE   Gerald LaFrance

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Posted October 07 2005 - 07:55 AM

THNX Jack I copied and pasted that from another website!!

I think I'll just go with the 16:9 screen to keep it simple thnx for everybody's help!!Posted Image
"IF the Facts don't Fit the Theory Change the Facts"    Albert Einstein

#7 of 17 OFFLINE   Cees Alons

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Posted October 07 2005 - 08:19 AM

Gerald,

There are also several posts in our Primer/FAQ that explain the different ratio thing and how it relates to the use of projection screens.
(And there's a lot more there! Posted Image You can also use the button at the top-left of this Basics Area.)


Cees

#8 of 17 OFFLINE   Mark Techer

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Posted October 07 2005 - 03:15 PM

Looks like he doesn't want to CH at this time, too bad... Mark

#9 of 17 OFFLINE   JeremyErwin

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Posted October 07 2005 - 03:46 PM

So, Mark, is a CH setup something you'd recommend to beginners?

#10 of 17 OFFLINE   Mark Techer

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Posted October 18 2005 - 12:44 AM

I think is depend if the beginner is new due to their age or just late at adopting. Either way, if they haven't been pre-programed about 1.78:1 as the only "widescreen", then there is no reason why they couldn't go and set up a 2.35:1 CH system and have great success. The problems arise when old school HT doesn't understand or doesn't want to learn something new.

New? Well actually CIH AKA cinema scope is over 50 years old now, so is hardly new, but relatively new to HT...

Who wants it?

Anyone that watches letterbox DVDs must surely wish that they could do away with the black bars top and bottom.

What you need.

CH is not that difficult to understand. First of all, anyone who has been to a real cinema and seen the masking curtains open up for a scope film has seen a CH setup. All they need to except is the fact that 2.35:1 is wider than 1.78:1 where the key is the 1, as that is the number that represents the height, and it remains constant, hence the name constant height set-ups...

So long as some knows what the term "aspect ratio" actually mean, the concept shouldn't be that hard to grip.

So yes you will need a W I D E R screen, one with an aspect ratio of at least 2.33:1 (21:9).

Formatting and compatible software.

Then comes along the "scaling" factor or the latest "buzz term", "vertical stretch" when in fact all we need is horizontal squeeze. Funny, we have had this since 1996, when DVD first launched. Surely most people at some stage conducted a little experiment with their DVD player set to 16:9 (even those with WS displays) and saw that the image is tall and thin on a 4 x 3 display or mode. It can be done on most widescreen displays, but may be limited to connection type.

The anamorphic lens.
The most difficult part to most is the anamorphic lens, and what it does. This is what seems to confuse people the most, the fact that it optically stretching an image to restore geometry. The automatic thought process is that "stretch" means distortion, not correction.

Yes it unfortunate that the lens are pricey, but that shouldn't mean that CIH is just for a select few. I made my lens from perspex prisms for less than 10th what a commercial equivalent lens costs. So it can be done, it is just a case of education...and the best place to start is to stop bagging cinema, as that is ultimately what we are trying so hard to replicate in our homes...

for more info go to
http://www.hometheat....8737#post58737
or the more popular
http://www.avsforum....ad.php?t=554901

Mark

#11 of 17 OFFLINE   PeterK

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Posted October 18 2005 - 02:40 PM

sorry, i don't think i get it. So, if the projector is in 16x9 natively how do 2.35 movies take up the whole panel? do you have to have a special dvd player or projector that will horizontally compress the 2.35 image to 16:9. So if you didn't have the lens on the projector, you would see a image that is too tall correct? And I see how that increases the projector resolution, but 2.35 movies still don't have the 480 resolution that 16x9 movies do because the black bars are still on the dvd right? I hope some of this makes sense thanks
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#12 of 17 OFFLINE   Cees Alons

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Posted October 18 2005 - 08:03 PM

Peter,

You're right. The same end result could be achieved without an anamorphic prismatic lense by zooming the projected picture in, to match a CH screen. And you always need the required screen width.

Difference would be: the original 364 or so lines of the 1:2.35 image would be all of the projector panel you would be using. The CH-solution-with-prisms would first have converted the image to 480 horizontal lines (indeed a special projector to do that, more and more of the very new sophisticated ones can, or a scaler would be needed).

Advantage of CH-with-prism: the conversion could be a more sophisticated, thus smoother, one. Also, you wouldn't as easily see the vertical pixel structure of the projector (the horizontal pixels are stretched and thus seen as readily as in the zoom situation). Brighter image because of less vertical magnification (against some loss in the anamorhic prism device as well as caused by its horizontal magnification).

Advantage of the zoom solution: no prismatic inbetween, no 364 -> 480 conversion (comparable situation: some gamers hate using LCD screens, because the necessary conversion of some games' image from their fixed screen resolution to the native resolution of the LCD panel is less sharp than ideal). Much less expensive.

In both cases you wouldn't really be increasing the vertical resolution, but decrease the projection of the projector's panel vertical line structure in one case, for which you would pay at least around $1000 or so, against a more direct projection (without image processing and optical stretching) in the other.


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#13 of 17 OFFLINE   Tony Loewen

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Posted October 20 2005 - 05:22 AM

You would use a panamorphic lens to zoom to the full 2.35/1 screen, then you would use a scaler like ffdshow to squeeze the picture into the 16/9 panel. If you use a quality scaling algorythm, then you're good to go and you would be using every pixel available on your panel, when watching 2.35/1. One guy I know put his panamorphic on a motorized slide so that he could have it in use during 2.35 movies, and it would just slide out of the way for 16/9 (or 1.85/1) movies. Then he would bring in masking curtains from the sides of the screen to get rid of the dead space. I would definitely go with a panamorphic/constant height for my next theater, if I'm gonna have a big screen, I want to fill it when I watch movies. Now that alot (most?) movies are coming out 2.35, you will have black bars at top and bottom on a 16/9 display. Read up on that constant height section at avs, that's where your best bet for information will be. Not exactly a beginner's topic, but not really all that advanced either. Good panamorphic lenses aren't cheap, but neither is anything else in this hobby. In my opinion, it would lend more to the experience. A 2.35 should be bigger than 1.85, so why not make it?

#14 of 17 OFFLINE   Mark Techer

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Posted October 20 2005 - 03:44 PM

Cool, and I thought this tread wasn't going anywhere... "sorry, i don't think i get it. So, if the projector is in 16x9 natively how do 2.35 movies take up the whole panel?" There are two forms of stretch that can be applied - 1. electrical, performed by the display 2. optical, done by using an anamorphic lens. In both cases, scaling is needed. The anamorphic process used on a DVD means that the image has been horizontally squeezed to fit more information into a given space. When displaying the image, the geometry will be wrong unless the image is stretched. The amount of stretch is fixed at 33% for video. It does not increase for 2.35:1 Vs 1.78:1. All anamorphic DVDs will be displayed as horizontally squeezed on a 4 x 3 display. Therefore a 16:9 image will fill the full panel of a 4 x 3 display, but the will look tall and thin. The removal of the black bars comes about by zooming the image on a 16:9 display. The image is still by default a 4 x 3 image that is tall and thin. It just happens to be not as tall due to the fact there are black bars top and bottom. So by using the 4 x 3 zoom mode, the top and bottom of the image is chopped. This work in our favor as we now have a wider version of the original 4 x 3 image, that is, an image that now fills the entire 16:9 panel in the same way that the 16:9 fills the 4 x 3 panel. But in both cases, the image is tall and thin. It needs to be stretched out to restore the geometry. This is what a Horizontal Expansion Lens does - optically stretches in the horizontal plain without affecting the vertical plain. As mentioned, the amount of stretch is constant, so by providing two amounts of image width, we end up with two geometry correct aspect ratios - 16:9 and 21:9. For those installs that leave the lens in place (like mine), the ratio switching is done by the projectors remote. I have two pre-set options - 4 x 3 ans 4 x 3 zoom, and I can switch between the two to display both 16:9 and 21:9 at the same height. Both images are geometry correct and there are no black bars in the 21:9 mode. 16:9 will have side pillars... Mark

#15 of 17 OFFLINE   PeterK

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Posted October 23 2005 - 06:12 AM

so if you do this, when you view 16x9 movies, they won't take up the full display panel right? so then wouldn't you have to keep removing and replacing the lens every time you switch aspect. Is that what you're talking about tony. even if you had it motorized, wouldn't you have to keep switching the dvd player back and forth between 4x3 and 16x9 otherwise it will show a horizontally squished image when watching 16x9 right?
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#16 of 17 OFFLINE   Adam Bluhm

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Posted October 23 2005 - 12:19 PM

My gosh. So much information.

I'm only 23 and when I finally build my house in a handful of years, and have my dedicated theater, I can only hope there is technology out there that makes this a whole lot easier. Posted Image

The more ya know the less ya know. Everytime I read these forums (which has been a long time) I both learn something new and learn that I don't know something. Posted Image
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#17 of 17 OFFLINE   Mark Techer

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Posted October 23 2005 - 07:22 PM

PeterK,

There are two ways to do this - expensive and affordable.

Expensive has a remote controlled device that either moves the lens out of the way like the ISCO III or turns the prisms to a "by-pass" mode like the Prismasonic H1200R. Some go this way because they believe that they are truly missing rez (horizontal only) for HDTV.
Additional scaling is also often required...

Affordable means that you leave the lens in place as I have done and scaling is done by feeding the projector horizontally squeezed program. So yes, when watching 16:9, you are only really using the centre of the panel, (remember here it is the 4 x 3 normal node) and therefore your rez drops from 1280 x 720 to 958 x 720. Note that your still using max vertical rez, but now the lens is optically stretching the image to restore the geometry. Those that do this claim that the loss in horizontal rez is not that noticeable - but you would have to be the judge on that...

The fun part is of course watching scope films at the same height. Now your using the full 1280 x 720 rez (running the image in 4 x 3 zoom to rid the black bars) and the lens stretches the image to restore geometry.

When comparing the two, the overall brightness of the two ARs doesn't change.

Adam,

Hopefully the next gen of DVD player (HD-DVD and or BR) will offer the much needed 20:9 (or is that 21:9) option. If that happens, you will most likely see a flood of new lens products on the market. 21:9 is the next BIG (or should that be W I D E) thing, so keep reading so you can be prepared Posted Image and make the right choice the first time round...

Mark




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