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Chart Distance x Screen Size - Standards SMPTE and THX

post #1 of 61
Thread Starter 
Based on information obtained on the website:
http://myhometheater.homestead.com/v...alculator.html

I have made a graph with the distances and sizes of screens recommended by the standards SMPTE and THX.

The proportion of the following screen measures is 16:9. With 1080p content and the measures are the diagonal of the screen.

Differences between the standards:




SMPTE
http://www.smpte.org/

Maximum size recommended by standard SMPTE:




THX
http://www.thx.com/

Minimum size of screen recommended by THX:



Screen size recommended by THX:


Viewing Distance when Resolution becomes important:
Screen Size x Viewing Distance
480p
720p
1080p
1440p





Source: http://www.carltonbale.com/2006/11/1080p-does-matter/

Peter

--------------------------------------------------------------------------------------------

Gary Contribution:


Quote:
Originally Posted by Gary Lightfoot View Post

This often comes up here and other places, and this diagram is gives a good idea of what viewing angles seating distances will give:



Using image height and width is preferable to diagonal measurements since they're a lot easier to work with, and removes confusion with screen aspect ratio - many people here have 2.35 screens.

THXs recommended viewing angle for HD 16:9 screens is 40 degrees, or 2.4 image heights. That also works for people with 2.35 screens who use an anamorphic lens, and may work with some pjs that zoom for scope.

The film industry often recommends 3 x IH for seating distance based on the crossover point between immersion (closer is considered better) and where image artefacts like film grain and projector induced issues become visible. With digital and good HD content that limitation is reduced, and is probably why THX recommend 2.4 x IH rather than 3. Sitting anywhere between 2 to 4 times the Image Height puts you within the usual range of a commercial theatre, and with 1080 displays, we're pretty much there with regards to resolution and image quality.

As Darin has pointed out, THX often gets misquoted but this video may be of interest:

http://www.youtube.com/watch?v=rBdmG...embedded#at=50

I also think it[s worth pointing out that the graphs that say where certain resolutions become noticeable doesn't mean you should sit there. In fact you should probably sit closer because those distances are where the Human eye can start to resolve those resolutions, but when comparing something like a 720 pj to a 1080 pj you might not be able to tell the difference until you get much closer.

Gary
post #2 of 61
Thread Starter 
I am seated at about 3 metres from the screen and the screen is 76 "wide.

The size of the screen was well on the standard SMPTE and I do not feel any discomfort visual.

I hope these graphics help.

Peter
post #3 of 61
They helped me, thanks for pointing me in the right direction!
post #4 of 61
hmm.. I basically 5 meters from 133" and have absolutely no problems with it nor anyone else. Even when playing games with mass movement like COD4
post #5 of 61
Peter,

Can you draw a cone showing the minimum and maximum screen sizes? I have 2 rows so how does 1 seat @ 5m help everyone?
post #6 of 61
Thread Starter 
Quote:
Originally Posted by kevivoe View Post

Peter,

Can you draw a cone showing the minimum and maximum screen sizes? I have 2 rows so how does 1 seat @ 5m help everyone?

http://www.thx.com/home/setup/display.html




Peter
post #7 of 61
are the screen measurements given width or diagonal?
post #8 of 61
Thread Starter 
Diagonal.
post #9 of 61
i figured, thanks.

i'll be right around 11 1/2 feet from a 119" screen.
post #10 of 61
Very nice and concise info, thanks Peter. This is one of the first things I looked into when researching installing a projector (and have yet to find anything this easy to follow and all in one place), so I'd recommend it for a sticky personally (although I might suggest attempting to convert the units to the american standards, as I believe that is what the majority of people using these forums are used to).
post #11 of 61
Thread Starter 
Thanks Varrius.

It is a good hint. I will convert the units.

Peter.
post #12 of 61
Very nice! I had already done the conversion myself (and I'm glad to find out that I'm choosing right about the THX recommended screen size). I'm sure the conversion may help some others, I do hope that I was correct in assuming that many or most of the users here would prefer it in feet instead of meters.
post #13 of 61
Thread Starter 
Picture of the distance of the screen to the ground.



It is about 1.97 feet from the ground and is very comfortable, especially to read the subtitles.

Before, it was about 3 feet, but I was uncomfortable.

Peter
post #14 of 61
Thank you Peter for creating that graph.

I am in the process of designing a 2.35:1 screen. Would you have any idea how the viewing distance would change going from 16:9 to 2.35:1?
post #15 of 61
Thread Starter 
To change the proportion of 16:9 to 2.35:1, simply multiply the value of the diagonal of the screen by 0.9472

For example, the graph shows that to 13.12 feet, the diagonal of the screen in 16:9 must be 97".

Then multiply 97 by 0.9472 which equals approximately 92" in proportion 2.35:1

Peter.
post #16 of 61
Quote:
Originally Posted by Peter_ View Post

Screen size recommended by THX:

Where did you get that from? If from the 36 degrees recommended by THX then that isn't a recommendation for the screen size you should have, it is a recommendation for the worst case viewing angle in a commercial theater. If a theater was built to that then almost every seat in the house would have a larger viewing angle and THX doesn't tell people where to sit in those theaters (at least from what I've seen). Also, when THX gave a recommendation at their booth at CEDIA last year they said it was based on testing to see where people see pixels with 1080p projectors. But, 1080p projectors vary and then the recommendation wouldn't apply when projectors go beyond 1080p or even to film now. So far I don't recall seeing or hearing anything about THX saying people shouldn't sitting closer than some viewing angle that wasn't based on limited pixel resolution, just stuff about not sitting further away than a certain viewing angle. Put another way, I haven't seen anything from THX limiting how close the closest seats can be in a commercial theater to get certified, only how far away the farthest seats can be.

Thanks for doing these graphs. I just know that the wording of the THX minimum and recommended specs for building a commercial theater have confused a lot of people and that even their later recommendation for home theater was based on limitations of current projectors. I also don't know if they tried using an anamorphic lens, which would generally make pixels less visible at the same viewing ratio.

--Darin
post #17 of 61
Thread Starter 
post #18 of 61
Quote:

That supports just what I said:
Quote:


The angle subtended by the left and right edges of the Cinemascope image and the farthest seat in the auditorium is recommended to be 36 degrees. The minimum acceptable angle is 26 degrees for THX certified cinemas.

This gets paraphrased in other places and people often misconstrue this as THX recommending that people sit at a place where the viewing angle is 36 degrees. That is clearly not the case from what it says about the farthest seat in the theater (this is for commercial theaters with lots of seats). If a commercial theater is built to THX recommendations then the vast majority of people will be sitting in seats with viewing angles larger than 36 degrees.

It is misleading when people say "THX recommended viewing distance" since that 36 degree recommendation is to build a commercial theater so that the minimum viewing angle is 36 degrees, not a recommendation that people sit in the farthest seat if a theater was built to THX recommendations. However, they allow theaters to be THX certified if their minimum is 26 degrees. That is, a minimum for the minimum viewing angle instead of a recommended minimum viewing angle. In both cases it is for the minimum viewing angle in that theater (for multiple seats).

--Darin
post #19 of 61
Thread Starter 
Darin,

Thanks for the explanation.

I'll edit this thread.

Peter.
post #20 of 61
Quote:
Originally Posted by Peter_ View Post

To change the proportion of 16:9 to 2.35:1, simply multiply the value of the diagonal of the screen by 0.9472

For example, the graph shows that to 13.12 feet, the diagonal of the screen in 16:9 must be 97".

Then multiply 97 by 0.9472 which equals approximately 92" in proportion 2.35:1

Peter.

Appreciate the math. I'm planing a 130" diagonal so 130 x 0.9472=123" and I plan to sit at around 16' so I'm in the SMPTE maximum zone. I think I better do some testing just in case the screen is too big for the room.

Thanks for the info.

I'm sitting at roughly 180" so thats about x1.5 screen heights
post #21 of 61
A green sub?
post #22 of 61
Thread Starter 
Quote:
Originally Posted by CADOBHuK View Post

A green sub?






Peter.
post #23 of 61
Peter,

Just wanted to say thanks for your contributions to the projector forums here.

Your photos, graphs, etc. have really been insightful, even to a trigonometry challenged person like myself.
post #24 of 61
Thread Starter 
Thanks James!

Peter.
post #25 of 61
Thread Starter 
New information added.





Source: http://www.carltonbale.com/2006/11/1080p-does-matter/

Peter
post #26 of 61
nice find Peter
post #27 of 61
Thank you Peter- I had an idea of these numbers, but it is very nice to see it all laid out in a concrete format. This should prove useful on future projects-
post #28 of 61
Thread Starter 
I did think this thread could be fixed. Because these standards are not old. But I'm not a moderator to decide about it.

I'll be watching this thread and I'll trying to help as much as I can.

Peter
post #29 of 61

This often comes up here and other places, and this diagram gives a good idea of what viewing angles certain seating distances will give:



Using image height is preferable to diagonal measurements since they're a lot easier to work with, and removes confusion with screen aspect ratio - many people here have 2.35 screens and using the height works for 16:9 and 2.35 when using an A lens.

THXs recommended viewing angle for HD 16:9 screens is 40 degrees, or 2.4 image heights. That also works for people with 2.35 screens who use an anamorphic lens, and may work with some pjs that zoom for scope. Sitting at 2.4 SH for 16:9 is 40 degrees and 52 degrees for 2.35 from the same seat.

The film industry used to recommend 3 x IH for seating distance based on the crossover point between immersion (closer is considered better) and where image artefacts like film grain and projector induced issues become visible. With digital and good HD content that limitation is reduced, and is probably why THX recommend 2.4 x IH (52 degrees) rather than 3 X IH. Sitting anywhere between 2 to 4 times the Image Height puts you within the usual range of a commercial theatre, and with 1080 displays, we're pretty much there with regards to resolution and image quality.

As Darin has pointed out, THX often gets misquoted so this video may be of interest:

http://www.youtube.com/watch?v=rBdmG...embedded#at=50

I also think it's worth pointing out that the graphs that say where certain resolutions become noticeable doesn't mean you should sit there. In fact you should probably sit closer because those distances are where the Human eye can start to resolve those resolutions, so sitting closer means those resolutions become more visible and detail visibly clearer. If you sit at the threshold of visibility of lets say 1080 and then comparing it to 720 from the same distance (all else being equal), you might not be able to tell the difference between the two until you get much closer.

Gary


Edited by Gary Lightfoot - 1/13/14 at 3:24pm
post #30 of 61
Thread Starter 
I really appreciated your post (contribution) to this thread.

I'll quote your post in the first page.

Thank you,

Peter
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