Teenagers are already getting the IMAX experience by burying their noses in their smart phone screens while streaming movies.

On the viewing distance question I also measure eyes to screen. But the distance is approximate and may be to the end of my eyelashes as I don't want to poke my eye out with a tape measure.

Eyes to screen.

The reason the smart phone movie can never be IMAX in scale no matter how close their eyes are to the screen is the family of cues that are binocular in nature. The term defining how we know the iPhone is small even though it is close is called �??Retinal Disparity�??. All the monocular cues are the ones that would let our brain in a perfect dark room to be fooled into thinking a smaller screen is bigger.

The path of our eyes sight is not always parallel as we look at objects closer we start to look at them ever so slightly cross-eyed. That change in angle is dependent on distance to the point our eye selects to focus on. In the case of a screen it is the distance to the surface. Then you add in that the distance to the center of the screen is closer than the edges and the corners are even a greater distance. All the cues come together even the ones we omit because we darken the room etc and produce a size assessment of the screen and image. I think the brain searches for information when there is the lack of information and one cue that is left is Retinal Disparity.

I wonder if in some people the cue is more pronounced than in others maybe it is visually based or maybe it is thought based. As I know when I sink into the depth of a motion picture the sensation of screen size vanishes for me and like you I see a 100 inch screen no different than a 200 inch screen in terms of movie enjoyment as long as my seating or eye distance is proportional.

I wish all this conversation was taking place in the thread I hoped to explore this topic in though as it is a little off topic here.

On a side note I just suggested to a friend who was getting a new computer system at work to try a larger UHD TV as a monitor. It was around 36�?? and about doubling the measurements of the old one with about equal resolution. I was surprised when I saw it set up it was now to the back of the desk roughly twice the distance from her eyes. And she was ecstatic about the suggestion as it was so easy to see and easy on the eyes. It didn�??t seem logical twice the size twice the distance should have been a wash. It had to be the change in focal length that made the difference but she kept saying it is so much bigger I love it. I didn�??t get into the details figuring leave well enough alone whatever the reason was. My first thought was focal distance but now I�??m wondering if there wasn�??t a Retinal Disparity component to the improvement as well.

In the above post I was exploring the cues that could verify what you feel and it could be in part due to the factors I mentioned.

At some point the angle of each eyes line of sight will become nearly parallel and maybe in the case of your 150�?? size the answer is good enough. It is also possible different people have different thresholds.

I think IMAX is correct when they are comparing their new 40�?? high screen to the old 80�?? in saying both can be an IMAX experience. In our local science center here there is a small (IMAX like) theater they play IMAX nature movies on. It is only 45�?? wide but every bit as immersive as the bigger IMAX theaters. it is not advertised as an IMAX and being in a small town there isn�??t the expectation of IMAX. It is a big hit I wish they would play mainstream movies there.

Well all I know is that if I every hit it really big on the lottery, there is only one theater I want to copy. Something about a 19 foot screen with added height and four way masking...but I guess according to some you can get the same feel with a well done room and a 100". It would be nice to sample both since seeing is believing.

Even time I want to dream I go here:
https://www.avsforum.com/forum/92-com...n-theater.html

125" 2.35:1

As we age our near vision tends to suffer most, so having a larger computer monitor further away may be the difference between someone needing reading glasses or not.

With home theater there's a lot of personal preference involved in screen size and viewing distance. One factor that influences our preference for larger screens is how many will be viewing. A bigger screen viewed from a greater distance better accomodates larger groups whereas when only one or two are viewing a smaller screen viewed from a shorter distance may be more acceptable.

Beyond that, male viewers are especially susceptible to the ever present subconcious influence of the "mine's bigger than yours" factor.

Not me... ...well, maybe.

155" 16:9.
I use 4 way masking to allow for scope, 16:9 and 16:9 IMAX
Seating is 10.5' away.

Scope 148" diagonal:


16:9 121" diagonal.


IMAX 155" diagonal:

Perhaps presbyopia is coming into play? If the larger screen is further away it seems clearer?

Edit (didn't notice Dave already addressed this)

Something I will never forget was few years ago ...Wife and I were at Costco shopping for living room TV. I was looking at a 60inch...wife walked over to the 70inch version....and said....get this one...its bigger

She must have been sent from heaven.

You do not need to see the room. Just seeing the image on the screen still provides cues to how far away and big it really is and that its a flat image.

Eye accommodation, the muscles that focus the eye give a cue to your brain as to distance of the thing focused on. The further away the more at a relaxed state the muscles that focus your eyes are. The weaker the accommodation cue.

Binocular disparity, the difference in what each eye sees give a cue to your brain as to distance of the thing focused on. The further away the more similar what each eye sees is. The weaker the binocular disparity cue is.

Yes I mean the cues in the movie image.

No because the illusion of immersion also increases as the amount of the viewers field of view the image occupies increases.

Although there maybe a issue as far as the image matching what the eye would see. If the image occupies too greater a field of view than what the camera captured using the standard lens then I think maybe it could look foreshortened rather than the correct perspective.

Going by Wikipedia so maybe wrong. Standard lenses (those which give a similar perspective to human vision) for 35mm film produce a field of view of 62 to 40 degrees. With the traditionally used 50mm lens being 40 degrees. That ties in with the field of views created by recommended viewing distances of SMPTE, THX, etcetera.

OK. That makes sense, but I have to say that from my experience, my screen seems closer with the lights on than it does when they are off and a movie is playing. That doesn't seem to concur with the above so do you have any thoughts on why that may be?

Do you mean the cues which may show a mountain range or the inside of a room? I would have thought that your eyes would be focused on the screen plane so the movie cues wouldn't make much difference, or is it just a perception thing where the brain believes what it is seeing?

That's what I thought - the closer you are and the bigger the image on the retina, which concurs with Fox, Dolby etc etc.

I think the brain instantaneously creates perception from combining visual cues. What cues are available and their relative strengths would change when you turn off the lights, reducing or removing the cues from the rest of the room and increasing your attention to and probably the contrast of the screen image.

Have you ever tired using the same set up but with the screen having a forward rake the top tilted towards the viewer, or a curved screen or curved screen with a forward rake? As that should create some inconsistency in eye focus distance. Creating a cue that what you are looking at is three dimensional. While the focus distance is also inconsistent with other cues as to relative distance of one object in the image in comparison to other objects in the image. When I tried it, it increased three dimensionality of the image and perception of image depth.

I maybe misremembering but I think I read that Cinerama screens were curved and had a forward rake, so not only were they larger occupying more of the viewers field of view they also had inconsistent eye focus distance across the screen.

Also while removing the room may enhance the image I do not think that is always the case. In some cases maybe the room could enhance the image. Bias lighting or a shadow box effect might increase the perception of depth and three dimensionality of the image.

There was a phase I think in the 1950s to 1960s where some cinema screens were designed to have a shadow box to in theory enhance the illusion of depth and three dimensionality.

Yes its just a perception thing the brain I think gets a lot of different cues and creates perception from them. While some cues are stronger than others, and the strength of cues can depend on things like viewer distance, there is not one cue that dictates perception, they all compete and complement each other.

For example a simple line perspective drawing of a three dimensional chair and table you do not perceive as just geometric shapes but as the three dimensional objects depicted. But you know that its a image not a true real three dimensional object. Increase the number of cues of depth and three dimensionality and the image appears more and more real. The more real it appears the easier immersion becomes the acceptance of it as reality.

A good projector set up I find can appear very three dimensional with both image depth and things coming out of the screen without using 3D binocular disparity. And can appear very real have for lack of a better way of putting it image solidity the objects looking like real solid objects not a picture.

I think that is because central vision is detail and color sensitive. Hunter gatherer is the food ripe. As you move away from central vision it is more motion detection is a predator stalking you, running at you. The illusion that things are real moving objects is greatly enhanced by the image filing more of the viewers field of view. So it aids in the illusion the objects are real and also the illusion that you are really moving, really there.

I also find non visual things enhance immersion as well. I like surround sound and have a active sub woofer for low frequencies and a tactile inducer bass shaker.

We've got a refurb 730HD set 15.5ft from the screen in a 14 x 18ft room. Image is 16x10 145in diagonal and 77in SH. It is ceiling mounted projecting onto a TV White painted wall. We sit about 14 to 16ft back, which is just far enough that the pixels are not visible. It is far superior to a TV for a fraction of the cost. The projector is bright enough for daytime use with the screen half of the room shielded from direct daylight (Condo).

Another installation is a ceiling mounted W1070 set ~13ft back which gives a 145in diagonal in a 13w x 21ft L x 9ft H media room with a painted wall/screen (Vacation home). This will have 2nd row raised seating when complete.

A 3rd installation is a 2030HC in a LR. It is ceiling mounted 8.5ft from the wall for a ~95in diagonal. This install is ongoing. I bought it as a refurb from Staples for ~300cdn but it appears to be factory new. It replaces a 50in LCD TV and we'll use a screen when complete because the wall is stippled and a huge PIA to get smooth again.

One of the things I really like about PJs is being able to browse the web from my easy chair, which I'm doing now via the 730HD, although I'm not sure my wife agrees...

Lots of hypothetical nonsense here...

If a 20' tall gorilla comes up to you in a complete pitch black void, you're saying you won't be able to tell if he's 10 ft away and 20' tall or he's 20 ft away and 40' or he's 1 ft away and 2' tall? You'll be like "Oh jeez, I can't tell how big this gorilla is, I need to read the THX manual and do some geometry calculation".

You guys should stop living in THX manuals and come back to real world.

A big screen is a big screen. It's always better than a small screen. Your scientific mambo jumbo is not fooling anyone.

Oh, and don't sit far back from the screen, it's such a silly thing to do. Like buying a 600hp car and then only drive it on 30mph city streets.

I think most of us when being honest with ourselves know we have an almost instinctive ability to determine true size as you point out. I wouldn’t go as far as calling it hypothetical nonsense though, because what I was looking for at least in the other thread I stared was the science behind the instinctive nature of being able to do this when all most all the cues are not there such as in a dark room.

@dovercat did a great job of explaining this to @Gary Lightfoot I thought. This idea goes slightly against conventional wisdom and in the commercial movie industry a small screen is even large. In home theater maybe not so much when comparing a 5’ high screen to a 7’ high screen the cues work different because our eye focus is not nearly at the infinity setting.

At some point I will recap what is said here into the other thread.

It always kills me when I guy starts out saying they want a 150" screen only to be talked into a 110" screen to meet the "standards".

I don't know I would not be surprised if there is a big psychological difference between a 5' high screen that is shorter than the viewer and one that is twice as large and taller than the viewer 7' high. A truly big screen in terms of its size to that of the person watching it.

That is my point actually the apparent size distance when seating is adjusted for the screen size the closer it gets to you it is easier to rationalize its real size.

For example in pitch black a 50’ tall screen viewed from 100’ and a 100’ tall viewed from 200’ the cues caused by focal length would be almost the same as our eyes would be at far focus / infinity. A where a 3’ from 6’ and a 6’ from 12’ would be much different in focal length.

Home theaters unless very huge are or could be greater change in focal length than larger screens like found in commercial theaters then there are the eyes being forced more inward and that combined cue tells us real size to some degree when nothing else can be seen but the screen.

As I have mentioned, my experience is that my screen feels larger and further away when watching movie content than it does when the lights are up and the screen is visible without content.

From the second row, it feels a lot larger and that I am in a larger room being sat further back than I am. My room is all black velvet so I have no other references other than the seats and people, but the distance to the screen, and the screen itself feels larger than they are.

When watching The Force Awakens in 3D at a commercial theatre, with the glasses on the screen felt smaller and closer than it was because the rest of the room was dimmed down and was giving less cues to size and distance so perhaps the cues in the content were then overriding what I knew about the screen size and distance, a bit like some optical illusions. That changed when I removed the glasses.

As DC has said, the cues in the movie can fool our brain, so perhaps that is overriding the cues our eyes are giving us to the screen being flat and potentially effecting other cues, such as perhaps size and distance. Things like gamma can affect the depth of an image and that's just a change of how the image is displayed, with nothing else being physically different but the content can take on a more 3D feel to it.

I am a computer programmer so I like math, science, formulas...yada yada but when I was building my theater room....when it came time to screen....I measured the wall I was gonna put screen on and picked as big a screen that I could fit on it...135 inch which left about 3 inches on each side and 1inch from top of screen to ceiling. If I could have gone bigger I would have. Then I put my chair as close as I could without having to turn my head to see everything in image.....that was gonna be my seating position

Then wife and family said...too close....too close....so after some trials ended up at aprox 13ft from the 135inch screen. Ide prefer being closer.

No math....no formulas.....if I had it my way ide still be at that original seat spot =P

That's how we often tell people to do it - project an image to the biggest size you feel comfortable with from where you sit, experiment with size and seating distances too if you can, and then buy a screen to match. It's also how we tell people to set up a 2.35/CIH system - sit where the 16:9 image looks as big as you like it, then scope will be wider and more immersive, just as designed and intended.

But knowing the specs for theatres can also help you make sure you are in the right place. It's not unusual to see people who buy a large screen and sit beyond 4xSH for example, which is way beyond the back row.

Some people even fit the biggest 16:9 screen and move their seats closer for 2.35 movies because the height is less, and then move the seats back for 16:9 stuff. Another way of doing it is to keep the image height the same in a scope set up, with the seats kept in the same place and 16:9 no taller than 2.35 (zoom the image, not the seats), and then you don't ever have to move the seats, just make sure you're close enough that 16:9 is as big and as immersive as you feel comfortable with. That way you also get to keep a static audio set up too, with all the speakers in the best place for the seats, other wise you'd have to move the speakers when you move the seats.

Interesting thread. I'm in the bigger is not always better camp.

We have two electric drop screens.

110" 16 x 9 DaLite High Power
125" 2.35:1 Elite Cinewhite

PJ is a Sharp Z30K DLP with lens memory. About 14' viewing distance.

Room size was a factor. We already had Salk mains for the L/C/R. I wanted to use them and needed the side space for the large speakers.
However, at the end of the day, it's about personal preference...Go to the commercial theater. Do you like to sit up front? Go larger. We like to be in the middle about 2/3 of the way to the rear. Our HT approximately duplicates this viewing angle. My $.02

And don't forget, this is avscience, so people here often tend to like to talk about the technical aspects. Some people who don't would rather be sarcastic than join in, for whatever reason.

You are the type of person and family that would greatly benefit from the system of presentation I use and advise people like you to try out. I call my system PIA for personal image area.

When your family told you too big you should have not moved the seating back you should have zoomed the image down and if the boarder became an issue then came up with some 4way masking plan. I assume you have some masking now 2way because scope and flat have different AR’s.

You are a person that I’m sure enjoys IMAX levels of immersion and you shouldn’t sacrifice your likes for others when you watch alone.

What you are describing is deep immersion and how movies are intended to be viewed. Too many of us that are highly involved in the science of movies and projection have a hard time turning our brain off and viewing a movie as we did as children. When the content of the movie fully fills our cranium’s abilities we are viewing a form of reality and in deep immersion as children we didn’t notice the poor quality of the projection and the dust sticking to the film. The movie took over our brains. When we have kids over and I get to run an animated movie with high immersion for their little eyes to take in I spend more time watching them than the movie.

When deep immersion takes place you do lose sight of the size of the image and the location you are sitting. You look thru the image and see it as close to reality and reality is the largest screen there is.

I agree. I have seen quite a few times when sarcastic comments come into a thread.

I don’t know what post was sarcastic though if it was something I said I apologize.

No, I wasn't referring to you Bud, at least not on this occasion