Visible Pixel Size: A Showdown Between Cih And Ciw Setups

[roachy]

Firstly, before I did these calculations, I had no preconceived expectations of what the results would be. My only experience with a Constant Image Height (ie Scope screen, scaled image and anamorphic lens) is on two occasions at The Big Picture People, and based on these demos, it was enough to convince me that this is a path of which I’d like to take. If you’ve seen any of my threads you’ll know that it still may not happen based on the fact that the current Aussiemorphic Mk3 lens is unsuitable for my room due a short Throw Ratio.

 

Anyway, I like to research anything I do properly. One of the major arguments that certain Constant Image Width (ie Projecting a 2.37:1 image onto a 16:9 screen and using masking for the resultant black bars top and bottom) proponents is that when using an anamorphic lens, you increase the visible pixel size due to the fact that the lens stretches each pixel by 33% on the horizontal plane. I thought I would test this theory using basic mathematics. People can argue black and blue about subjective perceived pros and cons, but mathematics never lie!

 

For my example, I have decided the optimal 2.37 image size I wish to achieve is a 110” diagonal. Based on Oztheatre’s scope screen for sale this gives me an image size of 2576mm x 1087mm.

 

On a Constant Image Height (CIH) setup, I would purchase a 110” 2.37:1 screen of this size. When I remove the lens from the projection path, I am left with a 16:9 image size of 1932mm x 1087mm (achieved by taking the image width and multiplying my 0.75), with lens required to stretch the image to fill the screen. As I have scaled the image to fit the panel I am using the full 1920x1080 pixels. Therefore my Visible Pixel Size for the unstretched 16:9 image is 1.006mm x 1.006mm square pixels. (1932mm divided by 1920 pixels and 1087mm divided by 1080 pixels) When I put the lens into the path the new Visible Pixel Size is 1.338mm x 1.006mm given that the lens stretches on the horizontal by 33%.

 

To get the same 110” 2.37:1 image on a Constant Image Width (CIW) setup, I would need a 16:9 screen with the dimensions of 2576mm x 1449mm, (achieved by taking the image width, dividing by 16 and multiplying by 9) given that in this setup you still need to project the black bars and then mask them. The resulting Visible Pixel Size is 1.342mm x 1.342mm square pixels. (2576mm divided by 1920 pixels and 1449mm divided by 1080 pixels).

 

I realise I have chosen to ignore the interpixel gap, which makes no difference to this argument, and is variable depending to the projector technology (ie there is a larger interpixel gap on a LCD projector versus say a DILA projector)

 

Therefore I have come to the conclusion, that for any given 2.37:1 image size, a Constant Image Width setup actually has (almost) identical horizontal Visible Pixel Size, and is actually larger on the vertical by about 34%, completely blowing out of the water the claim that a Constant Image Height setup has larger Visible Pixel Size, when in fact the complete opposite is true.

 

I know that some people, no matter how many facts you present them, will not change their mind. But you cannot argue with the maths involved, and unless you can prove to me that one plus one does not equal two then this (particular) argument is closed.

Edited August 5, 2009 by roachy

[CAVX]

I know that some people, no matter how many facts you present them, will not change their mind. But you cannot argue with the maths involved, and unless you can prove to me that one plus one does not equal two then this (particular) argument is closed.

Well said I am sure the following (future) posts will make interesting reading.

[MACCA350]

Therefore I have come to the conclusion, that for any given 2.37:1 image size, a Constant Image Width setup actually has (almost) identical horizontal Visible Pixel Size, and is actually larger on the horizontalVertical by about 34%, completely blowing out of the water the claim that a Constant Image Height setup has larger Visible Pixel Size, when in fact the complete opposite is true.

Should add that this extra vertical resolution is not currently in the Blu-ray source until we see true anamorphic Blu-ray's. But there are still benefits to increasing vertical resolution by scaling and the use of the whole 16x9 projector panel.

cheers

Edited August 5, 2009 by MACCA350

[roachy]

Original post fixed. Thanks Macca

[BladeRnR]

A well researched and irrefutable post regarding the maths around CIH Vs CIW formats and solutions. We really do need our own Anamorphic section on DTV Forum like AVS Forum enjoys as we could include this kind of post in an FAQ.

Superbly written Roachy.

Cheers

Blade

[Dama]

On a Constant Image Height (CIH) setup, I would purchase a 110” 2.37:1 screen of this size. When I remove the lens from the projection path, I am left with a 16:9 image size of 1932mm x 1087mm (achieved by taking the image width and multiplying my 0.75), with lens required to stretch the image to fill the screen. As I have scaled the image to fit the panel I am using the full 1920x1080 pixels. Therefore my Visible Pixel Size for the unstretched 16:9 image is 1.006mm x 1.006mm square pixels. (1932mm divided by 1920 pixels and 1087mm divided by 1080 pixels) When I put the lens into the path the new Visible Pixel Size is 1.338mm x 1.006mm given that the lens stretches on the horizontal by 33%.

 

To get the same 110” 2.37:1 image on a Constant Image Width (CIW) setup, I would need a 16:9 screen with the dimensions of 2576mm x 1449mm, (achieved by taking the image width, dividing by 16 and multiplying by 9) given that in this setup you still need to project the black bars and then mask them. The resulting Visible Pixel Size is 1.342mm x 1.342mm square pixels. (2576mm divided by 1920 pixels and 1449mm divided by 1080 pixels).

 

Am I right in saying that in this example the Lens method gives you VPS 1.338mm x 1.006mm and the Zoom method gives you VPS 1.342mm x 1.342mm?

[roachy]

Am I right in saying that in this example the Lens method gives you VPS 1.338mm x 1.006mm and the Zoom method gives you VPS 1.342mm x 1.342mm?

That would be correct. The zoom method would be the same as using a 16:9 screen and masking

Edited August 5, 2009 by roachy

[Curious]

Awww. c'mon dude...you've left no room for error - how is this thread gonna stretch on page after page with the usual suspects threatening to beat each other half to death with arguments based on a litany of semi-technical quasi-factual ramblings?

[CAVX]

how is this thread gonna stretch on page after page with the usual suspects threatening to beat each other half to death with arguments based on a litany of semi-technical quasi-factual ramblings?

I'm here, just waiting for my nemises

[Mr.Bitey]

I'll start by saying, that I didnt read any of the first post, and that i havent ever seen a scope screen, anamorphic do-flicky or any said masks in felt, velvet, latex or other gimpish fettishes....

This I believe qualifies me to contribute to this thread on a very technical level with well formed and articulated preconceptions based on mere hearsay and gleaning a superficial understanding of the basic concepts and more importantly the common abbreviations and concatenated content whilst skimming what would appear to be well constructed empirically based and proven source material for debating the subtleties of each format.

Most importantly, these facts are drawn together by the simple yet ultimate and altogether utterly moot point, which is, that I can not has one!!

Cheers,

Lustey

[BladeRnR]

I'll start by saying, that I didnt read any of the first post, and that i havent ever seen a scope screen, anamorphic do-flicky or any said masks in felt, velvet, latex or other gimpish fettishes....

This I believe qualifies me to contribute to this thread on a very technical level with well formed and articulated preconceptions based on mere hearsay and gleaning a superficial understanding of the basic concepts and more importantly the common abbreviations and concatenated content whilst skimming what would appear to be well constructed empirically based and proven source material for debating the subtleties of each format.

Most importantly, these facts are drawn together by the simple yet ultimate and altogether utterly moot point, which is, that I can not has one!!

Cheers,

Lustey

You sir have a most uncommon wit. I was drinking coffee at the time - now half of it's out my nose so thanks for that!

Blade

[BladeRnR]

Awww. c'mon dude...you've left no room for error - how is this thread gonna stretch on page after page with the usual suspects threatening to beat each other half to death with arguments based on a litany of semi-technical quasi-factual ramblings?

I think I'll let Mark take this one or have we done enough to scare the monster back into it's lair?

shhhh - It's Wabbit Hunting Season. I might Jinx myself and I'm already on a High from finishing the HT.

Blade

[Mr.Bitey]

Now THAT'S a CIH smiley if ive ever seen one!! LOL

Cheers,

Bitey

[jutta]

Yep, the OP is certainly gonna cause some problems for the naysayers

[CAVX]

Now THAT'S a CIH smiley if ive ever seen one!! LOL

Cheers,

Bitey

Correction, that ' ' is a letterboxed smiley. Question is, when are we gonna get a true anamorphic smiley? I know I will be smiling that day

Edited August 5, 2009 by MarkTecher

[Mr.Bitey]

Indeed it is, as I may have mentioned in passing, i havent the slighest idea :-) However I do find its masking pleasing.

I dont think id ever want to go anamphalactic - tho im ok with peanuts...

Cheers,

Bitey

[roachy]

Yep, the OP is certainly gonna cause some problems for the naysayers

Well at the moment they are more like naysaynothingers! And surely that's not a bad thing. And think of all the RSI injuries I'm saving them due to the lack of typing!

[kopthat]

I'd like to add that I never see Pixies when watching movies,

although I think there may have been some in Finding Neverland...

[Highjinx]

There is no argument, It's simple logic! no thread was needed, this was mentioned this days back. I think there may have been some confusion it was mentioned the bigger the screen the bigger the pixels do get.........and one has to sit further back for the eye to resolve the image.

Be it CIW or CIH, for the same width image in both cases the horizontal pixel width and horizontal interpixel gap is the same. The vertical pixel count in displaying 2.35:1 images on the CIW is 810 and the CIH is 1080, there are 270 additional pixels and interpixel gaps on the CIH image, therefore the vertical pixel size is 25% less, but there is 25% more interpixel dead zone gaps as well.

As bluray is not anamorphically encoded the information found on the 810 pixels is remapped to fit on 1080 pixels, no additional information, simply more place holders to carry the same information. There is the benefit of increased brightness as the light that is focused on the projectors panel. Nothing else.

The negatives are many, adding any glass in front of the projector lens has a reduction effect on the ANSI and intrascene contrast(just look at an A-Lens and watch the light bounce around, the more glass elements the worse the effect), it also affects the Modulation Transfer Function, image depth and detail reduction is an unfortunate by product. Granted some lenses are better than others....but all affect the image negatively in the mentioned areas by varing degrees.

The introduction of distortions such as pincushion etc, loss of subtitles are also part and parcel of an A- Lens for what current* gain(s)......brightness?......if one has a large screen that requires every lumen of brightness then the requirement is understandable.

If true added detail anamorphic sources were available, then the negatives would be outweighed by the additional detail, alas this is not the case at present.

Current application of anamorphic projection using BluRay are pseudo anamorphic, providing only a brightness gain and losses in far too many areas important to image quality.

It's up to each individual to weigh up what they want out of their HT..........there is no right or wrong.

But it is grossly misleading to say the addition of an A-Lens in the light path has only positive benefits.

[Sean_Melb]

HJ - another one of your idiotic crazy posts - you obviously spend all day looking out for a chance to bag scope at any moment.

you dont own one - you dont care to - you talk about maths - but unlike you i am a movie WATCHER and collector. I personally dont care if the pixels are a 100 times bigger or streched this way or that - who gives a Cra*!!!!

I have a MIII lens - go richard with the lens - and its like wow - i watched my Sim2 projector for 18 months without one - now its like wow im watching movies i havent watched for ages again just for the wow factor.

My projector is 720p but who cares - my god you talk maths ansi this ansi that lens, brightness this brightness that - who cares - I spent more on my HT build than probably you did on your last 3 car purchases combined am I going out and getting the latest 1080p projector - no - because at 4m watching dist and 5.5m the second row we dont use binos to watch movies!

That my son is the by word for the day - we WATCH movies!! And for those who are movie watchers not tv or pay tv watchers - we love our movies and scope is like having the top shelf wine instead of a VB for 16:9

Go troll your spruke somewhere else - us movie afficionados will do just that- watch a movie on the way they have been filming them since like 30 years before i was born!

Go scope or go watch TV.

Edited August 6, 2009 by Sean_Melb

[Mr.Bitey]

But it is grossly misleading to say the addition of an A-Lens in the light path has only positive benefits.

Thats right. Its why the OP says a scaler is needed too.

Cheers,

Bitey

[BladeRnR]

HJ - another one of your idiotic crazy posts - you obviously spend all day looking out for a chance to bag scope at any moment.

you dont own one - you dont care to - you talk about maths - but unlike you i am a movie WATCHER and collector. I personally dont care if the pixels are a 100 times bigger or streched this way or that - who gives a Cra*!!!!

I have a MIII lens - go richard with the lens - and its like wow - i watched my Sim2 projector for 18 months without one - now its like wow im watching movies i havent watched for ages again just for the wow factor.

My projector is 720p but who cares - my god you talk maths ansi this ansi that lens, brightness this brightness that - who cares - I spent more on my HT build than probably you did on your last 3 car purchases combined am I going out and getting the latest 1080p projector - no - because at 4m watching dist and 5.5m the second row we dont use binos to watch movies!

That my son is the by word for the day - we WATCH movies!! And for those who are movie watchers not tv or pay tv watchers - we love our movies and scope is like having the top shelf wine instead of a VB for 16:9

Go troll your spruke somewhere else - us movie afficionados will do just that- watch a movie on the way they have been filming them since like 30 years before i was born!

Go scope or go watch TV.

The sweet smell of fresh air to blow away the stench of crap. An excellent post that addresses the heart of the matter for TRUE movie fans. Like Sean I spent money on the EXPERIENCE not the Specifications.

HJ this is how I watch movies - emphasis on the WATCH as Sean just highlighted. I don't count pixels, I don't stroke myself emphatically while reading THX specifications, I don't have a light meter held up on high measuring ANSI of any other bull*&^% you bang on about.

2:35.1 is in the house.

Find an argument for it HJ. Any argument. The evidence is staring you in the face.

Blade

[Mr.Bitey]

I don't count pixels, I don't stroke myself emphatically while reading THX specifications, I don't have a light meter held up on high measuring ANSI

:looks sheepishly around:

:says to self: never mention U do these things, they are private things, for private people:

EDIT: and slowly, and very quietly, hides sound pressure meter, set to A and fast.......

Cheers,

Local Shoppey

Edited August 6, 2009 by Mr.Bitey

[CAVX]

2:35.1 is in the house.

Nice So where is the images of the lens?

[Highjinx]

The sweet smell of fresh air to blow away the stench of crap. An excellent post that addresses the heart of the matter for TRUE movie fans. Like Sean I spent money on the EXPERIENCE not the Specifications.

HJ this is how I watch movies - emphasis on the WATCH as Sean just highlighted. I don't count pixels, I don't stroke myself emphatically while reading THX specifications, I don't have a light meter held up on high measuring ANSI of any other bull*&^% you bang on about.

2:35.1 is in the house.

Find an argument for it HJ. Any argument. The evidence is staring you in the face.

Blade

Crap ANSI! :

But it's only a screen shot.

Want to use an A - Lens go with DLP, LCos has poor ANSI to begin with, an A - Lens only diminishes it further.

Mark has the right idea a good DLP!