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16:9 Screen Vs. 2.37:1 CIH Screen

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169 cih screen
91K views 96 replies 19 participants last post by  tbase1 
#1 ·
These drawings show how the two different systems work, when it comes to screen size, image size, and aspect ratio..

The first one is for 2.35:1 DVD's..

 
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#2 ·
This is for 1.85:1 DVD's..


When a 1.85:1 image is vertically stretched, you do lose a bit of the image top and bottom..
Some people prefer to use what's called the "Pass through mode"..That just means that the light path is no longer through the anamorphic lens..
So the corect AR is maintained..
 
#5 ·
Here are some screenshots showing the various stages of converting your standard 2.35:1 DVD image to a full cinemascope image.
The camera hasn't picked up the blank part of the screen in the first two sequences, but you can see how the image changes..

All the pics were taken from the same position with the camera mounted on a tripod, and all at the same zoom setting..

The first shot in each sequence shows the normal image without any zoom on the projector..and without the anamorphic lens in place.


Now the images are vertically stretched by the projector or DVD player to the full height of the screen.

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And finally the lens is in place, optically stretching the image to the full width of the screen, and restoring the correct geometry.












 
#6 ·
Well done Prof, they are very CIH demo shots.

The best description I ever got was from the RUNCO guys at CEDIA. They did their speil as if no-one else had it, and they made simple.
They said CIH is two parts - Sclaing + Optics.

I guess the most difficult part is understanding the scaling aspect of the process. This is the electrical manipulation of the signal to -
A. rid the black bars and
B. use the full panel for max rez and image brightness.

Optics are a science all by themselves, and the part that makes understanding the difference between an anamorphic lens and conventional zoom lens is that the anamorphic lens only magnifies in one direction - typically horizontally.

The exact amount of magnification must equal the amount of electical scaling applied to the image.

The amount applied to video is based on 1.33x because 1.33 x 1.33 = 1.78, so 1.78 x 1.33 = (when rounded) 2.37. It simply takes the next step as well as provides an extension for 1.33:1 displays - IE you can obtain 1.78:1 optically by using a 1.33x stretch lens with a 1.33:1 projector...

Mark
 
#8 ·
While in theory this makes sense, the cost is so expensive for the lenses is it worth it?
I'll put it this way. When I zoom up and eliminate the slight black borders on my 10
foot wide screen while watching the HD DVD of "The Wild Bunch", it looks almost as a
35mm print shown on the same size with anamorphic lenses and at the same distance
of 15 feet from booth to screen. What size screen are you using for comparison and
is worth the cost of the lens to remove the black borders and use more of the pixel field.

One of the disadvantages of using any anamorphic lens is that you lose some resolution when you compress and expand the image which is why 70mm widescreen looks so much better than a 35mm
anamorphic print even when the 70mm print was optically enlarged from a 35mm negative.
 
#10 ·
While in theory this makes sense, the cost is so expensive for the lenses is it worth it?.
Unfortunately this is how many people view anamorphic lenses, and something way beyond their reach.. As a consequence, they don't even consider it as a possibility and don't look any futher into it..

Commercial lenses are very expensive, sometimes thousands more than some projectors..

I was of this belief about a year ago, and for me an anamorphic lens was just a dream..Something that I would never be able to afford, unless I won Lotto..

Then I came across Mark's Aussiemorphic lens, and for the first time it looked liked it would be possible to have an anamorphic lens..
I read everything I could find about it, and other peoples views on the lens who had purchased one..
and looked at a number of screenshots with the lens fitted..

I finally decided to buy one, still a bit hesitant as to whether I was going to get a quality lens or not, particularly when compared to lenses costing thousands of dollars..

Well to say that I was thrilled with the results would be an understatement..
I won't say what it cost me, except it was a fraction of the price of a commercial lens..

My point is this...You don't have to pay an arm and a leg to have an anamorphic lens..There are other ways of obtaining a lens that will perform almost as good as very expensive ones..
You can just buy the prisms, and put the lens together yourself..Or you can buy a lens kit (like mark's) and set it up yourself...

Believe me...If I can afford it...anyone can..
 
#9 ·
Hi Richard,

What projector are you using? Think of it this way - regardless of the rez, you will able to use the full rez of the projector all the time. If you take trueHD, you start with 1080 vertical pixels for 16:9 and progressively loose vertical pixels as the image gets wider. By the time you reach 2.35:1, you're down to about 810 vertical pixles.

One method is to zoom in the image. This is very much projector and placement dependent - some projectors just don't have enough zoom from a given throw. If your projector does have the range, what you end up with is enlargening of the pixels in both the horizontal and vertical directions. Seating distance pending, you may even see pixel structure.

The other method to to use an anamorphic lens. Yes some models are expensive, but there are also cost the effective approach that can work as well - see HERE. When you employ a 33% stretch lens, you are able to horizontally expand the image by 33%, but not affect the vertical rez. Researh has proven that we are more sensitive to vertcial rez than horizontal, so using an anamorphic lens keeps the pixels at the same height. And instead of throwing away about 270 pixels, you image is now made of the FULL 1080 vertical pixels. It is denser and more film like. I have seen systems that DO look as good (if not better) as 35mm film on a small screen (I define a small screen as anything less than 4.0m). It is like watching a brand new release print...

Mark
 
#16 ·
I'm sure that the Z2 does work for SD, but may not work for HD. I have started a thread on using a HTPC with a program called YXY, which is how I got around the VS issues for HD on my system...

Mark
 
#21 ·
Unfortunately, no set date. The MKIII will be released in stages –
1. Injection Molded Plastic case that allows both future upgrades as well as backwards compatibility.

2. Focal correction or “astigmatism correction” element

3. CA correction where the new prisms will be made from two different types of glass that have been bonded together.

All of this takes time and money, and so a slow process when developing and funding a project like this yourself...

Mark
 
#24 ·
This seems to be the right place to ask the following question:

If you have a high resolution (HD) and "screendoor free" 16:9 projector like the Panasonic PT-AE2000that is able to fill up the total width of your 2,35 screen without seeing any pixel structures, and you can electrically zoom out from 16:9 to 21:9 without having to adjust focus and/or lens shift. What does an anamorphic lens bring you? More lumen, more sharpness, more contrast? And will this be easily noticable?

Thanks.
 
#25 ·
The HD panel is 1920 x 1080. When you zoom, you only see 1920 x 810 with the remainder being projected off the top and bottom. As you zoom, the pixels increase both horizontally and vertically.

Adding an anamorphic lens allows your projected image to be made from the entire panel instead of just 75%. The lens expands the pixels, but only in the horizontal direction, so the vertical size remains the same. This is benificial as we are more sensitive to vertical than we are to horizontal pixel structure...

Mark
 
#27 ·
Acually you should work your seating distance from image height, not the width, where you should be no closer than 2x the image height and no farther back then 4x.

The beauty of CIH with a lens is that those pixels stay the same size (vertically) as you change ARs, so you do not loose sharpness*.

*pending the type of lens.

When you zoom, your pixels do increase vertically, so it is almost like going back from 1080 to 720, but not quiet, it is actually about 810...

Mark
 
#28 · (Edited)
In my set-up the viewing distance is 3x the image height using 2.37:1 projection (34 inch high; 80 inch wide), and 2.5x the image height using 16:9 projection (41 inch high; 73.5 inch wide).

So I don't have real CIH projection (constant image height). But in this way I keep the bottom of the projection at the same height (measured from the floor 31 inch) when going from one format to the other just by zooming. I have a variable masking screen that allows me to horizontally adjust the projection surface by pushing one button on the remote.

In this way I believe I have created close to optimal viewing distances (according toTHX and SMPT standards) for both 2.37:1 and 16:9 formats. And yes, I understand I am not using the projector's full resolution capability with 2.37:1.

But again, will the picture quality visibly improve with an anamorphic lens?

Will the added sharpness be more predominant than the possible adverse effects of lens imperfections and faults introduced by the pixel recalculations for the vertical stretching of the 2.37:1 picture to fit the 16:9 LCD chip?

I am not a disbeliever. I just don't know! :dontknow:
 
#30 ·
Just to add to that...

The whole idea of having a Scope setup is not just to remove the black bars, but to have that very wide screen image...Like you see in the Cinema...that really immerses you in the action on the screen..

It is generally accepted that the minimum width for a scope screen is 8' wide, with 9' being ideal if your room is large enough..
Anything smaller is not going to give you the same effect, and if 2 Metres is your maximum size you are able to fit or have in the room..then it probably isn't worth the additional costs involved..
 
#32 ·
Your are stepping on my soul Prof! :sad: Putting so much time and effort in building my dream HT and now hearing that my screen is too small to ever reach the Cinema feeling.... :crying:

But seriously, does the immersive feeling not more depend on the actual viewing angle (viewing distance : screen height ratio), than solely on the screen width? If I am sitting on the last row of a Cinema with a huge screen I have a much lesser immersive feeling than sitting 2,5 metre away from my 2 metre wide screen.

Could the generally accepted minimum width of 8' has to do with the assumption that you are not building your HT for just one or two people (little place within optimal viewing boundaries)? Because that is what I have done.

The other possibility I can think of is that there exists someting like a minimal viewing distance in order not to put too much strain on your eyes to focus on the screen. I just never heard or read about such a phenomenon. Am curious though if anyone has more info on this, or other factors that influence the immersive sensation we are talking about here.
 
#35 ·
What you will find is that your eyes will probably strain more watching HD on PC monitor at 3x the image height than watching the same program on a screen that is over 2m tall. In this case, it not the size of the image, but the distance to the image that must be taken into account. I think you will find however that the "immersion" is reduced becuase the smaller screen size, but your field of view (what you actually see) should be about the same.

Hope that makes sense...

Mark
 
#38 ·
Since we are talking about Home Cinema on this forum, let's say the maximum height you can achieve is 8' (2.45m), resulting in a maximum screen width of 19' (5.80m) . Your minimum viewing distance lies around 16' (4.9m).
Yes, 2x the image height is the closest you want to be regardless of screen size with 3x being preferred...

So if you have a room of measuring 20'x20' (6mx6m) or more, why stick to a procliamed ideal 9', and not go for 19' wide?
Because 12 feet wide is about the largest you can have in a 20 foot deep room.

Formula is -
20 / 3.68 x 2.37 = 12.88

Mark
 
#39 ·
Because 12 feet wide is about the largest you can have in a 20 foot deep room.

Formula is -
20 / 3.68 x 2.37 = 12.88

Mark
Thanks for pointing this out Mark. So, the ideal HT room measures 20' (6m) wide and 30' (9m) deep, permitting a 19' wide screen. Am I right?

PS I am just trying to get things really clear here, not only for the theoretical sake. I have friend who is buiding a new house and I like to give him the best advice on how to prepare his own HT.
 
#43 ·
Never even considered CIH, because I also always felt that the lenses were WAY over my budget.

I now see that Mark has made this an affordable endeavor, that I may look into now.

Thanks Mark

Gary
 
#47 ·
The only problem is with HD where a video scaler is required...That adds lots of money!
 
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