Seating distance 720, 1080, UHD and visual acuity. - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 128 Old 04-04-2016, 06:44 AM - Thread Starter
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Seating distance 720, 1080, UHD and visual acuity.

Preface:
I have been troubled for some time now trying to put into place what I’m told and what my eyes see in real life. I think I’m not the only one thinking about this, but I may be the one being most vocal. Rather than have the thoughts scattered around a 100 different threads it was suggested I start one specific to the questions I have and also the answers I have found for myself. To the mods I picked this forum not knowing the proper place for such a thread but feel it is appropriate because this is the starting point for many into front projection and where I see most of the questions this relates to. If you feel it is in the wrong place please feel free to move it to where it fits best. The majority of my conclusions regarding my own personal search for my answers came from this recent thread that was taken quite off topic, but with some really great input nonetheless. If the posters of that thread that helped me or the mods want to move any of the pertinent posts over here please do so. If not anyone that wants to see the back story just read thru this linked thread. https://www.avsforum.com/forum/68-dig...lp-please.html

My thoughts:
The benefits of new technology are always many and front projection UHD will be no exception I’m sure. I’m not against change in any manner. Front projection is a hobby for most of us and most hobbies have a money cap and most of us here have a compulsion to want to stay up with the latest and the greatest. Right now we are being bombarded with lots of information about UHD and the benefits and many people are advocating it based around the improved resolution. I have read 50 different articles and seen 50 different charts showing the benefit of the improved resolution. I was getting confused as I know what my eyes see and in reading dozens of threads old and new on seating distance and having seen for myself where 720 crosses over for me and viewing a lot of 1080 content also and its crossover point. I kind of extrapolated in my head my benefits of UHD and came to the suspicion it was being over sold in terms of resolution benefits and only resolution benefits. I really don’t have a grasp on the rest of that advancements that will go along with it yet. If the chart and information is wrong they are not just wrong for UHD but they are wrong for all the lower resolution. All the information out there or at least the well quoted ones are based around human visual acuity and the Snellen findings and eye charts we all remember with the big E on the top. I believe that data to be true and it states that humans can resolve details in that test down to 1/60 of one degree in the control of that test. Black E’s on white test charts etc. based on that one measurement only the size of a pixel was assigned and that is the base of why we need UHD. A good source of information explaining this methodology and one of the many sources often quoted can be found here along with the current charts that are widely used. http://carltonbale.com/does-4k-resolution-matter/ I am in no way singling out just this site and I did try contacting them to get a better idea of the logic behind information posted and never got a reply back.

In no way am I trying to infringe on any copyrighted material and I have seen this chart and many identical on many different sites. I amended this chart only to uses as reference and to point out a few common screen sizes and seating distances to an amended set of numbers I show in red for the purpose of discussion or even debate based around the information I have gathered from the above linked thread and others plus my own visual acuity I have experimented with at home changing distance to view. If this was off a little I wouldn’t even bring up the point but the difference so small as 1/60 and 1/30 of one degree as a starting point changes seating a huge amount. I feel this revised chart still errors on the side caution, giving any benefit of the doubt to the new technology or those that have better than 20/20 vision.

I hope those reading will comment on their own findings on what works for them. I just wanted to put my thoughts out there and see what people a lot smarter than me have to say.


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

On edit 4/14/2016
I thought I would relate what I learned on this thread and summarize it on the opening post so anyone finding this thread wouldn’t have to read thru over 100 posts with a lot of them not pectinate to the topic.

These charts are all over the internet in different forms and my understanding and others were that they were suggestions when a screen size and resolution combination change would be recommended. For example someone using a 720P projector given close enough seating and large enough screen size should change to a 1080P projector as their viewing requirement is now compromised because of visual acuity and the size of one pixel in their field of vision. I assumed this is how it worked as the chart is based around well-known 20/20 vision testing and the Snellen eye chart. I also assumed this was the case because many times I was directed to use these charts to point out to me that my resolution was too low for the screen size I was using.

What these charts are really designed for is to point out the very first point when one resolution can be noticed compared to another by a person with normal vision. In the course of this thread I found out the charts are also wrong at doing that based on newer scientific studies. So the thread split into two different lines of reasoning one being when can an individual with normal vision first detect a difference between a lesser resolution compared to better resolution. The second item being when can an individual with normal vision condemn a resolution as not being minimally acceptable.

Both of these suggestions are only guidelines and of course anyone can watch any resolution from any distance they like and if you are a person that wants ultimate screen image that is indictable from reality you could adjust your resolution and screen size to the extreme first detection point or if you are more budget minded and are looking for a resolution guide that lets you know the point when you start to see individual pixels instead of an image blended together you could use the other guideline. People new to front projection without a projector resolution to look at and see for themselves might find this information useful. Different projector technologies display pixels differently and the information I have found on line leads me to believe LCD projectors begin to show pixels 10% to 20% sooner than DLP. The reason being DLP has a higher fill rate and thinner margins.

Based around what I found in the course of this thread is the original chart is off by a factor of 5. Meaning it is humanly possible to detect a better resolution 5x sooner than what the chart shows.
The second half of my question on when you could start to condemn as screens resolution based around pixel size I found for DLP to be roughly 2X later than the original charts starting point or 10x the corrected chart.

I tested the theory a few times now as quite a few retail stores are showing UHD flat screens next to 1080p flat screens of the same size. Up close watching ether of the displays they look totally usable but of course the UHD looks close to realism in side by side comparison but nothing condemning to the 1080P image by any means. As I moved away to the point the original chart suggests I shouldn’t be able to tell a difference I still easily could. As I got back closer to the 3X - 5X that distance there was no difference depending on content. These observations at those distances are really subjective as it is not at all about pixels anymore but other subtle qualities in the image. There is also great differences in the brightness and contrast of UHD demo content compared to the feed they send to most 1080P sets. So there is little scientific in my comparison by eye but I do trust the scientific studies done that suggest the greater distances.

As to the second aspect when you would likely say you are getting to close to any given resolution based on pixel size I feel the numbers I marked up on the attachment below are fairly correct for DLP and take off a little for LCD projectors. This is only a guideline I will use for my own comparisons and to point out to people my personal beliefs and anyone can feel free to agree or not agree as they wish.

When I get time I will make a new chart for the condemning limits and post it here with the disclaimer that it is only a reference point based around my best judgment.

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

On edit 2: I added the two attachments and they look similar but serve two completely different purposes. The first chart is my personal recommendation on when a jump in projection resolution is advisable if you are looking for a point where the image you watch will begin to fail due to pixel size becoming distracting and no longer blending. The second graph is for reference only pertaining to the study within this thread as to at what point a higher resolution can first be noticed In that chart I marked up the widely used chart to show what the points would be based on current science. To see the original published graph you will have to click on the link above in the opening post.

These two graphs are in some ways related as one is the starting point and the other a reasonable stopping point for any given resolution.

The End
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Last edited by bud16415; 04-14-2016 at 08:28 AM.
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post #2 of 128 Old 04-04-2016, 08:45 AM
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Yeah, I think that at this point everyone agrees that 4k resolution in flat screens is not really the game changer manufacturers touted it to be. In reality, 4k's biggest contribution to the flat screen market was a huge negative as it was one of the factors most directly responsible for signalling the end of plasma as a viable competitor to LCD. Sure, you're fooling yourself if you say you can resolve the added resolution of 4k on your 55" LCD from 10 feet away but the damage was done: plasma can't do 4k so it's proof that plasma must be obsolete tech. Sad.


I am mildly excited for the UHD standard. A larger color space, more dynamic range and frame rates up to 120fps in addition to the resolution bump are all good reasons to be excited. The issue: most of all these innovations are only going to be affordable in flat panels where the effects are the least noticeable. 1080p only became 'affordable' in front projectors in the last couple years. Who knows when a UHD capable projector will come out at a price mere mortals can afford.
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post #3 of 128 Old 04-04-2016, 09:32 AM - Thread Starter
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Quote:
Originally Posted by PioManiac View Post
I've been sitting 10' from my 120" (16:9) screen for the last 8 years, Epson 1080UB projector.

I'm over 50 y/o and have never needed corrective lenses (or laser corrective surgery)
and I am right on the edge of being able to resolve pixel structure on certain screen images
...mostly bright white scenes.

If I lean forward vs reclined, it's more visible.
The original chart shows you should have had trouble with pixel size at anything closer than 16’. You say your vision is 20/20 or better and leaning forward from 10’ you are on the threshold of pixels becoming apparent on a mostly white or bright image. It sounds like you fall much closer to my numbers also. And during a normal movie image that isn’t as bright or white you would be very close.

Thanks for commenting.

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post #4 of 128 Old 04-04-2016, 09:50 AM
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Quote:
Originally Posted by PioManiac View Post
A few pic's with the lights on,
Wall mounted Pioneer Kuro Still my Favorite TV, even though its 8+ years old

articulating Sanus wall mount allows it to extend forward by 2 additional feet













First your projector pictures look fantastic thanks for sharing

It from 2008 and still the colors and black level look very good if im in your place i really wont replace it for new 1080p model and i agree with you on wait for 4K E SHEFT 4

You using black screen to improve the black level? If yes what is the (Completely black out velvet bat-cave,) what that mean

Thanks
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post #5 of 128 Old 04-04-2016, 09:53 AM
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Quote:
Originally Posted by PioManiac View Post
A few pic's with the lights on,
Wall mounted Pioneer Kuro Still my Favorite TV, even though its 8+ years old

articulating Sanus wall mount allows it to extend forward by 2 additional feet


First your projector pictures look fantastic thanks for sharing

It from 2008 and still the colors and black level look very good if im in your place i really wont replace it for new 1080p model and i agree with you on wait for 4K E SHEFT 4

You using black screen to improve the black level? If yes what is the (Completely black out velvet bat-cave,) what that mean

Thanks
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post #6 of 128 Old 04-04-2016, 10:03 AM
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Quote:
Originally Posted by kord555 View Post
First your projector pictures look fantastic thanks for sharing

It from 2008 and still the colors and black level look very good if im in your place i really wont replace it for new 1080p model and i agree with you on wait for 4K E SHEFT 4

You using black screen to improve the black level? If yes what is the (Completely black out velvet bat-cave,) what that mean

Thanks
Digital cameras and smartphones adjust the image when you take s picture of the screen. They are essentially useless, it doesn't look like that in person
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post #7 of 128 Old 04-04-2016, 10:28 AM - Thread Starter
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Pictures are always fun to look at and talk about though.

Here is one I like that you can print out and hang from your wall and test your vision.
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post #8 of 128 Old 04-04-2016, 11:26 AM
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4K is not what it is hyped to be for the resolution difference. The other factor that comes into play when determining resolution is movement. All these charts of 1 arc/minute are great but they are static images, motion would even be less. There have been many industry professionals that state an increase in frame rate would give much more noticeable picture quality improvement then a resolution increase. Most people can't notice the difference of 720P over a 1080i for resolution and many even prefer the 720 stations which has a higher frame rate. The new 4K standard does bring some noticeable picture quality improvements with HDR and WCG but the resolution is not needed except for sitting close or very large screens.
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post #9 of 128 Old 04-04-2016, 11:43 AM - Thread Starter
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Originally Posted by Ellebob View Post
4K is not what it is hyped to be for the resolution difference. The other factor that comes into play when determining resolution is movement. All these charts of 1 arc/minute are great but they are static images, motion would even be less. There have been many industry professionals that state an increase in frame rate would give much more noticeable picture quality improvement then a resolution increase. Most people can't notice the difference of 720P over a 1080i for resolution and many even prefer the 720 stations which has a higher frame rate. The new 4K standard does bring some noticeable picture quality improvements with HDR and WCG but the resolution is not needed except for sitting close or very large screens.
I agree about the motion as well and also the closer you sit the more the on screen motion is and then you add in eye motion increases. I am one that is happy with a 720 for the reasons you mentioned and if you go by my seating distance numbers where I like to sit is just inside the acceptable range. If you go by the numbers floating around I should be back another 10 foot. Thus the reason for this thread. I have for years done a poor mans HDR of sorts at least the elevated nits off a darker low gain screen. I use that mode for elevated lighting when watching sports and such. I much prefer film like levels with lights out for serious watching.

For those that have an understanding of this it is pretty simple. For those trying to figure it out the charts can send them down the wrong trail or maybe stop them from looking.

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post #10 of 128 Old 04-04-2016, 12:15 PM
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Originally Posted by bud16415 View Post
Pictures are always fun to look at and talk about though.

Here is one I like that you can print out and hang from your wall and test your vision.
Meh. I posted some infocus x1 shots in a screenshot thread once and claimed they were an expensive JVC.

Nobody noticed, thanks iPhone for correcting all the light levels and giving me the illusion of infinite contrast.
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post #11 of 128 Old 04-04-2016, 02:47 PM
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This appears to be developing into a broad and wide-ranging discussion. The chart from Carlton Bale and similar ones show specific results for specific resolutions at specific screen sizes and distances. I think it would contribute to the broader discussion to focus on a specific example. Since home theater has already crossed over from mostly 720p to 1080p there should be a lot of experience on this forum in dealing with those two resolutions. Let's start off with a 100" screen, which is a common size. The chart shows the following for a 100" screen:

* The full benefit of 720p is visible from about 20'

* The benefit of 1080p starts to become visible from about 18'

* The full benefit of 1080p is visible from about 13'

If we are going to question the validity of the chart, then we need to either prove or disprove the accuracy of those data points from the chart. It isn't just about whether or not we can see individual pixels. The benefit of higher resolution is a finer, more realistic overall image with, for example, straight lines vs. jagged lines. The question should be whether we actually perceive an improvement in overall image quality when viewing a 1080p image over a 720p image on a 100" screen from 13'. Even if we can't see individual pixels in a 720p image on a 100" screen from 13', if the chart is correct we should perceive that the overall quality of the image is not as pleasing as a 1080p image of the same size viewed from the same distance.

There are two ways to look at this. One way would be to consider all the anecdotal observations in this forum over recent years from those who've upgraded from 720p to 1080p projectors. My best recollection is that almost all of those many thousands of posts have been positive about the upgrade in resolution. But there were also many variables involved, such as different screen sizes and viewing distances. Also the newer 1080p projectors may have had other improvements beyond just higher resolution over older 720p projectors. And finally it's human nature to be enthusiastic about a new "toy" even if it isn't that much better than an old one. In other words, anecdotal observations are not scientific.

And that brings us to the second way to look at this -- scientifically. How would we go about scientifically proving or disproving the accuracy of the chart? Has anyone already done it and if so where can we find that data? If not can anyone at least point to scientific data that might bring the premise behind the chart into question?

At the very least I'd be interested in knowing how many believe this chart is fairly accurate or way off?
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post #12 of 128 Old 04-04-2016, 03:40 PM - Thread Starter
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Did you read all the latest posts over on the other thread from Gary Lightfoot and Dovercat. He made some excellent points in that thread in post #26.

I started this thread because I felt we were getting wildly off topic in that thread as we took it from a simple question that was answered to quite a technical topic. I might just rejoin that thread as the OP didn’t seem to care and I can turn this one into a screen shot discussion thread.

To your point I would vote for a scientific approach but find it odd needing to counter a established standard with science when the premise of the standard wasn’t based on science at all. It was a direct extrapolation from one well known scientific fact to something else vaguely related. It is not much different than if I said I was bitten by a black dog and now I will proclaim all black dogs are mean. If you don’t believe that then prove it with science and its not just ok to find a 100 black dogs that are friendly and expect that to hold up as some of them were not quite as friendly as others.

The original premise of the chart I don’t think was based in too much science and I don’t know if all Dovercat’s facts are factual but I don’t see a motive for him to make them up. The same with the experiment Gary Lightfoot talked of where 35 people couldn’t tell between two projectors of different resolutions at a given distance. That test if someone had the capabilities would be great to replicate again only with newer equipment. And yes there is the human factor of it has to be better because I just paid an arm and a leg for it.

We are also now talking about issues of perceived quality in an image that we really cant give a name. I do it all the time when describing an image as “film like” or “plasma like” soon to be called “HDR like” we know what that is to us when we see it but I don’t think you can measure it. And I don’t feel resolution plays much of a part in it. So someone that likes a plasma like image will be drawn to that image and we cant let that trait of a image seem to be caused by improved resolution.

I’m open to any ideas of a scientific approach or method of trying to come up with the closest scale we can find.

I did find it interesting after making the assumption of 1/60 of a degree should ideally be the size of a pixel, there was then another extrapolation made and a calculator made where you could put in your tested vision and it would do a calculation based specific to your eyes. We in the old days used to say GIGO.

I don’t have any new screen shots to post at this time.
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post #13 of 128 Old 04-05-2016, 04:55 AM
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post #14 of 128 Old 04-05-2016, 08:38 AM
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Quote:
Originally Posted by bud16415 View Post
To your point I would vote for a scientific approach...
NHK did just that:
http://www.nhk.or.jp/strl/results/an...0_chapter1.pdf

"In FY2010, we evaluated the relationship between image resolution and the sense of realness in experiments where subjects compared actual objects and video imagery."

"The higher the angular resolution, the greater the sense of realness, and the sense gently saturates above about 60 cpd; above 155 cpd, images are indistinguishable from the real object."

Note that NHK is referring to cycles, which is a pair of pixels, this study indicates that there is improvement past 300 pixels/degree, but with most of that improvement occurring up to 120 pixels/degree, which is actually an even higher resolution than the popular charts are based on (which IIRC is about 60 pixels/degree).

The problem with the charts is they draw definitive boundaries where none exist. It's like trying to draw boundaries of bitrate with MP3s and say 64kbps is good enough for portables with cheap headphones, but you need 128kbps for a HTIB, and 256kbps for... etc. The reality is different people have different levels of perception and more importantly caring. Most people just don't care to notice the difference between 128kbps MP3s and lossless, but for people that do, that difference is important.

Likewise, most people are happy with watching their TVs in the factory torch modes, but there's a group of people who notice and can't stand that. The same will apply to resolution, and as with everything else there increases in resolution come with diminishing returns, NHK's results show a much larger improvement in "realness" going from ~60 pixels/degree up to ~120 pixels/degree than going from ~120 to ~310.

What I know is that sitting ~11ft from a ~9ft wide screen, which is approximately 45 degrees, that while I can't "see" from that distance, I can see jagged edges on certain shapes which means I can see that the image is made up of pixels and isn't continuous. For my setup that means 1920/45 = 42 pixels/degree, which is well under what NHK found to be the saturation point (120 pixels/degree). A 4k display (with lens) would put me at ~85 pixels per degree, that should come much closer to eliminating the jagged edges.
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Originally Posted by stanger89 View Post
NHK did just that:
http://www.nhk.or.jp/strl/results/an...0_chapter1.pdf

"In FY2010, we evaluated the relationship between image resolution and the sense of realness in experiments where subjects compared actual objects and video imagery."

"The higher the angular resolution, the greater the sense of realness, and the sense gently saturates above about 60 cpd; above 155 cpd, images are indistinguishable from the real object."

Note that NHK is referring to cycles, which is a pair of pixels, this study indicates that there is improvement past 300 pixels/degree, but with most of that improvement occurring up to 120 pixels/degree, which is actually an even higher resolution than the popular charts are based on (which IIRC is about 60 pixels/degree).

The problem with the charts is they draw definitive boundaries where none exist. It's like trying to draw boundaries of bitrate with MP3s and say 64kbps is good enough for portables with cheap headphones, but you need 128kbps for a HTIB, and 256kbps for... etc. The reality is different people have different levels of perception and more importantly caring. Most people just don't care to notice the difference between 128kbps MP3s and lossless, but for people that do, that difference is important.

Likewise, most people are happy with watching their TVs in the factory torch modes, but there's a group of people who notice and can't stand that. The same will apply to resolution, and as with everything else there increases in resolution come with diminishing returns, NHK's results show a much larger improvement in "realness" going from ~60 pixels/degree up to ~120 pixels/degree than going from ~120 to ~310.

What I know is that sitting ~11ft from a ~9ft wide screen, which is approximately 45 degrees, that while I can't "see" from that distance, I can see jagged edges on certain shapes which means I can see that the image is made up of pixels and isn't continuous. For my setup that means 1920/45 = 42 pixels/degree, which is well under what NHK found to be the saturation point (120 pixels/degree). A 4k display (with lens) would put me at ~85 pixels per degree, that should come much closer to eliminating the jagged edges.
Thanks for the input and I will take a little time and digest it.
Very good input indeed.

I take it the study compared still images.

I am aware of all kinds of tastes be it audio or video and stuff like this can focus on any demographic they want or select a mean group and focus on that as long as everyone knows the group it is intended for.

I would like to think I have keen vision but if I use these kinds of figures it would tell me my tastes really fall on the indiscriminate set of viewers. But then again given your last paragraph watching that size screen with such an image and given the time to really study an edge of an object or a test pattern I would discern it quite the same as you would. I wonder if our brain and vision function differently with rapidly changing images much like real world vision (Driving a car say in heavy traffic compared to a stamp collector looking at the print pattern on a stamp.) That same example could also apply to your music example. When shut in the sound proof booth for my annual hearing test I can detect sounds my brain filters out all day long and if hearing them all I would go insane. I wonder if there is a visual filter also that lets us discard things that it doesn’t require?

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post #16 of 128 Old 04-05-2016, 10:22 AM
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What could effectively be considered "still" images are quite common in movies. It's not that a single frame is frozen on the screen, but there are many scenes where the camera remains stationary while fixed on an image where most of the data on the screen is not moving -- for example when two characters are standing in a room carrying on a conversation. This would be the time when viewers would most likely notice the negative effect of lower resolution. Of course in slam bang action scenes where the camera is frantically panning past crashing cars, flying bodies and buildings coming down few are likely to pinpoint single clues to lower resolution. Most would probably consider the lower resolution as part of the blurring effect resulting from all the fast-moving action flashing past their eyes at a frantic pace.
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What could effectively be considered "still" images are quite common in movies. It's not that a single frame is frozen on the screen, but there are many scenes where the camera remains stationary while fixed on an image where most of the data on the screen is not moving -- for example when two characters are standing in a room carrying on a conversation. This would be the time when viewers would most likely notice the negative effect of lower resolution. Of course in slam bang action scenes where the camera is frantically panning past crashing cars, flying bodies and buildings coming down few are likely to pinpoint single clues to lower resolution. Most would probably consider the lower resolution as part of the blurring effect resulting from all the fast-moving action flashing past their eyes at a frantic pace.
I agree and I think I mentioned that same thing in one of the two threads here. So let’s assume we will deal with the image as if it is a still image and any help we would get from motion could only make the image better in terms of resolution.

We now have to look at the graph provided in stranger89’s link and because he mentioned the diminishing returns idea. We need to figure the slope of the line between 1/30, 1/60. 1/120, 1/240 of one degree pixel size. The comparisons of the slopes should give us a clue to the percentile of nirvana we are below. If I had the data points I might have software to fit a curve to it and we could actually come up with I’m guessing some fourth order equation for predictability.

One thing I’m not clear on is they measured in cycles per degree and he mentioned 2 pixels per cycle. Is it an interlaced signal is that the reason? Or should we divide the CPD by 2 where 60 would be really 1/30 etc. I’m also not clear on what the sense of realness factor is I’m assuming it was something subjective to the tested humans and they were to rank something. I haven’t had time to read real deep into it yet. It is really clear there is upswing to the graph but it is also a very flat curve.

Would be great to see the method and the raw results of something like this. Makes you wonder where the close enough point is to paraphrase an old scientific joke.

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post #18 of 128 Old 04-05-2016, 11:25 AM
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One thing I’m not clear on is they measured in cycles per degree and he mentioned 2 pixels per cycle.
A cycle is one black band one white band, hence it needs two pixels one black one white to display one cycle.
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Bud, I'd like to correct your misconception that the foundation upon which the Carlton Bale chart and others like it is based is somehow unscientific as applied to video images. In fact it has been the standard used by motion imaging engineers for decades as documented in a Sony white paper:

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One arcminute of visual acuity means that human observers can discern 60 digital pixels per degree. This is also called 30 dark-to-light cycles per degree or 30 line pairs per degree. This reference for visual acuity has been used by motion imaging engineers for decades.
The Sony white paper is worth reading not only for this but for some good comparison images and a scientifically conducted study of the ability of real people in a theater environment to differentiate between two otherwise identical movie presentations at different resolutions:

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Focus group research confirms that real-world theater-goers can see the 4K difference. Movies were presented to a theater audience in both 2K and 4K, without identifying which was which—and without saying anything about the technical differences between the pictures. Audience members were not told to expect a resolution difference in these "unaided" tests. Even under these demanding circumstances, respondents consistently gave 4K higher marks for every aspect of picture quality. Respondents also gave 4K higher scores than 2K on every measure of expected consumer behavior including, "This is something I would tell my friends about," "This is worth paying more for," and "I would go out of my way to go to a theater that offered this type of picture quality."
The description above is exactly what I was referencing in my earlier post. People may not be able to specifically define that it's the higher resolution that makes one video image more enjoyable than another, but their eyes and brains subconsciously translate viewing a higher definition video as producing a better experience in every aspect of picture quality. The entire paper is well worth reading. It's reproduced in a pdf file at the following link to the Sony website:

http://pro.sony.com/bbsccms/static/f...K_WP_Final.pdf
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One thing I’m not clear on is they measured in cycles per degree and he mentioned 2 pixels per cycle. Is it an interlaced signal is that the reason?
Cycle-per-degree is the standard nomenclature from analog days where, (as dovercat mentions) a cycle consists of a black and white band, ie the cycle repeats at the next black or white band.

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I’m also not clear on what the sense of realness factor is I’m assuming it was something subjective to the tested humans and they were to rank something. I haven’t had time to read real deep into it yet. It is really clear there is upswing to the graph but it is also a very flat curve.
They compared a real object, to a video of said object, and their participants were asked to rate how real the the video looked. They found that at 155 cycles per degree/310 pixels per degree, that the video was indistinguishable from the real object. Further they found that 60 cpd/120ppd is the point at which the improvement leveled off, ie the majority of the improvement came from increasing resolution up to 120ppd, which is about twice what most of the charts actually say.
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Thanks guys for the clarifications.

This story happened today but it also happens several times every day. Someone posted some specs on their room and that they have a cheapo 1080 projector they have been playing around with and they are rather amazed at how great an image they are getting and were wondering what size they should be viewing and what others liked at that distance. The guy today was liking something like a 120” CIH setup and wants to buy an AT screen and is viewing from about 8’ back. He was getting a lot of positive feed back from like minded folks happy as larks some telling him I’m doing 104” some saying 110” some saying they are at 120” and normally someone is way out there with a 140” size. All claiming great PQ. Me being armed with facts and figures have to point out the truth to these folks. I tell them wait a minute any 16:9 screen larger than 67” is going to be too big and because they want CIH they are going to have to reduce down closer to 62” or something like that. I then tell them I know this because human visual acuity will be dreadfully diminished if they venture into UHD territory without the resolution.

I don’t disbelieve the facts or the tests, nor do I not believe the people at Sony. But we have a guideline that identifies and is based around vision acuity at some very high level 1/60 of a degree. Now I learn reality vision would be 1/300 of a degree why not change the charts to that if it is the max number. In that case I would have to advised the guy above the biggest screen he should use would be a 15” 16:9.

Gary Lightfoot posted above he personally sits at 2X SH with 1080.

I understand the science fairly well and trying to place it into what I know is the common reality. I guess everyone knows their image could be better and there is some point that is widely excepted as being excellent not perfect but very good to excellent.

Maybe we need a series of charts saying here is one you can follow if you want your visual image to be in the 99th percentile of perfection or we could call it a 6 sigma distance chart.

I really don’t dispute the chart as much as when it is used it deters people from front projection because as soon as they compute a screen size they would like they see they need a $8,000 projector and if they are going to only get a 67” screen they might as well go buy a 70” flat panel.

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post #22 of 128 Old 04-05-2016, 07:21 PM
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These video charts are based on statistical averages and are simply guidelines to let people know what a statistically average person might see at certain screen sizes at certain distances. Since not all people have the same visual acuity the charts can't possibly apply to all people all the time. Then there's the important matter of how the visual data from the eyes is integrated and interpreted in the brain. This also varies from person to person, further increasing the size of the range from the average the charts try to illustrate.

And finally after the eyes are finished seeing and the brain is finished processing, some people simply care a lot more about the final visual results than others. Some are so focused on the content that they're unaware of whether the image is in HD or SD and some are so focused on image quality that the slightest imperfection overshadows the content and spoils the experience.

No chart will tell anyone what will work best for them and no one should try to tell someone else what will work best for them. The best we can do to help others is to point them in the direction of general data including charts to better understand the basics but with a warning that there is no perfect measuring stick that magically fits all. They need to understand that only their own eyes can tell them what will work best for them.
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post #23 of 128 Old 04-06-2016, 05:19 AM - Thread Starter
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No chart will tell anyone what will work best for them and no one should try to tell someone else what will work best for them. The best we can do to help others is to point them in the direction of general data including charts to better understand the basics but with a warning that there is no perfect measuring stick that magically fits all. They need to understand that only their own eyes can tell them what will work best for them.

No truer words could be spoken. The point is a chart such as all these are not general guidelines. They are definitive boundaries where you will start seeing detrimental qualities with a lower resolution solution. They are setting points in seating distance based around acuity of vision and no one other than myself is suggesting that making a radical change such as halving the stated distance only affects acuity a very small amount and perhaps an amount hardly seen or cared about by maybe 75% of the people in the world. People see charts and they assume if the chart says this is perfect vision and if I was to deviate from the chart by doubling my seating distance I surely must be cutting my PQ based on visual acuity in half. That would be the case if the curves of the testing were straight lines with a constant slope. We now know from the information shown that the curves are not straight lines. I have always suspected this as most human function follows these same curves, be it track and field or the ability to play chess. Not much different than the curve grading scale we used to see as kids. So we are talking about a graph where we are looking at the extreme end of where it is flattening out and once reached will run parallel to the base line. The extreme example and even discarded by the scholars for now is the effect between 300 minutes and 120 minutes even though there was measurements that show some humans have vision equal to running a 4 minute mile. The graph is so flat at that point hardly no slope can be detected. It is a clear example purely mathematical of cause and effect on a diminishing return. Simply put something like Y = square root of X or most likely a higher order equation but the math is not important the concept that the graph is diminishing to zero slope at and around all the points we are talking about.
You mentioned statistics and that’s an excellent approach and maybe closer to what I was first suggesting. At first I was assuming the 60 minute factor wasn’t statistically significant because it was widely touted as the end point of vision. Now we know it isn’t,the real number is maybe 300 minutes so even Snellen may have selected a point he felt had some statistical significance or maybe 150 years ago it was the best he could measure and he liked round numbers, we don’t know.
Statically speaking is 60 minutes the right point for the vast masses based around visual acuity and also “bang for your buck”? All consumer products offer the same compromises. I would love a Lamborghini Aventador but I drive a Kia Soul. Both would get me to work and back but I have to say the Lamborghini is a ways up that curve near the 300 minute mark and my Soul is I’m guessing about the 30 minute mark. If I go to a budget car forum and the chart shows I should suggest a Chevy Corvette as an absolute minimum and to drive to work in a Kia Soul would be ridicules in today’s world of technology, I would have to be a fool to expect any degree satisfaction in driving a Kia Soul. But if we really take a look at what is being driven statistically and charted it based around what you get for what cost and what level of satisfaction we may have a much different chart.
I don’t want to lower the standard of excellence nor do I want to inhibit the growth of technology I want just the opposite for both. As mentioned the market place and the manufactures and free enterprise will decide for us in the long run. But the consumer also has to be factored in and their job is going to be to drive the price down. Once 4k takes hold as mentioned all the goodies will stop showing up in 1080. Then there will be a rush of those that can afford it to do so. Once a market is saturated would you rather sell a 100 $10k projectors or 100-million $1k projectors. Trust me that plan is in place already.

Getting back on topic I liked the Sony white paper you linked a lot. A must read for everyone that hasn’t seen it. One point I had on the paper I wanted to make note of and for you and others to think about. On page 4 last paragraph they spell out a little about any eye testing methods. And in specific the area of the eye being tested is the fovea visual center. That’s the E you look at on the eye chart. Now on the monitor you are viewing this on look at the E just typed, don’t adjust your point of focus and try and read the word just 2 lines up. Now try and read the line 20 lines up without moving your eyes off the E. Now think about how many screen heights you are away from your screen and how small an area of your total screen those two lines and 20 lines really are.

Bud
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Bud,

I've been reading this and other threads on this topic, and appreciate your efforts here.

Without repeating all the technical aspects, what is the bottom line, take-home, real-world implications of what you're trying to communicate? What are the implications for someone's decision making with regard to source resolution, screen size, and seating distance?

I'm running into a "can't see the forest for the trees" type of confusion here, being inundated by all the details and technical discussion, which is preventing me from seeing the 'big picture' (pardon the pun!).

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Originally Posted by bud16415 View Post
This story happened today but it also happens several times every day. Someone posted some specs on their room and that they have a cheapo 1080 projector they have been playing around with and they are rather amazed at how great an image they are getting and were wondering what size they should be viewing and what others liked at that distance. The guy today was liking something like a 120” CIH setup and wants to buy an AT screen and is viewing from about 8’ back. He was getting a lot of positive feed back from like minded folks happy as larks some telling him I’m doing 104” some saying 110” some saying they are at 120” and normally someone is way out there with a 140” size. All claiming great PQ. Me being armed with facts and figures have to point out the truth to these folks.
The truth is, if they're happy with they're setup they are right. The "facts" as you call them are not to tell people they are wrong, to contradict those who have tested and made up their own minds, they are to help those who haven't tried/tested build something that is most likely to result in success.

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I tell them wait a minute any 16:9 screen larger than 67” is going to be too big and because they want CIH they are going to have to reduce down closer to 62” or something like that. I then tell them I know this because human visual acuity will be dreadfully diminished if they venture into UHD territory without the resolution.
Huh? The charts never say when a size is too big for a given resolution, all they say is when a given resolution is likely to be "useful" (provide a visual improvement over a lower resolution).

Quote:
I don’t disbelieve the facts or the tests, nor do I not believe the people at Sony. But we have a guideline that identifies and is based around vision acuity at some very high level 1/60 of a degree. Now I learn reality vision would be 1/300 of a degree why not change the charts to that if it is the max number. In that case I would have to advised the guy above the biggest screen he should use would be a 15” 16:9.
The issue is people use these charts to say "at x feet, you don't need y resolution, it won't be an improvement." Reality is those charts are based on assumptions and averages, and other tests (NHK) show that much higher resolutions can be beneficial. But again, they don't say anything about minimum acceptable resolution.

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Maybe we need a series of charts saying here is one you can follow if you want your visual image to be in the 99th percentile of perfection or we could call it a 6 sigma distance chart.
People like to boil everything down to a number, but you often can't do that.

Quote:
I really don’t dispute the chart as much as when it is used it deters people from front projection because as soon as they compute a screen size they would like they see they need a $8,000 projector and if they are going to only get a 67” screen they might as well go buy a 70” flat panel.
I don't follow that at all.

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No truer words could be spoken. The point is a chart such as all these are not general guidelines. They are definitive boundaries where you will start seeing detrimental qualities with a lower resolution solution.
That's the problem you have it backwards, the charts are just general guidelines, they are not definitive boundaries.

Quote:
They are setting points in seating distance based around acuity of vision and no one other than myself is suggesting that making a radical change such as halving the stated distance only affects acuity a very small amount and perhaps an amount hardly seen or cared about by maybe 75% of the people in the world. People see charts and they assume if the chart says this is perfect vision and if I was to deviate from the chart by doubling my seating distance I surely must be cutting my PQ based on visual acuity in half. That would be the case if the curves of the testing were straight lines with a constant slope. We now know from the information shown that the curves are not straight lines. I have always suspected this as most human function follows these same curves, be it track and field or the ability to play chess. Not much different than the curve grading scale we used to see as kids. So we are talking about a graph where we are looking at the extreme end of where it is flattening out and once reached will run parallel to the base line. The extreme example and even discarded by the scholars for now is the effect between 300 minutes and 120 minutes even though there was measurements that show some humans have vision equal to running a 4 minute mile. The graph is so flat at that point hardly no slope can be detected. It is a clear example purely mathematical of cause and effect on a diminishing return. Simply put something like Y = square root of X or most likely a higher order equation but the math is not important the concept that the graph is diminishing to zero slope at and around all the points we are talking about.
You mentioned statistics and that’s an excellent approach and maybe closer to what I was first suggesting. At first I was assuming the 60 minute factor wasn’t statistically significant because it was widely touted as the end point of vision. Now we know it isn’t,the real number is maybe 300 minutes so even Snellen may have selected a point he felt had some statistical significance or maybe 150 years ago it was the best he could measure and he liked round numbers, we don’t know.
Statically speaking is 60 minutes the right point for the vast masses based around visual acuity and also “bang for your buck”? All consumer products offer the same compromises. I would love a Lamborghini Aventador but I drive a Kia Soul. Both would get me to work and back but I have to say the Lamborghini is a ways up that curve near the 300 minute mark and my Soul is I’m guessing about the 30 minute mark. If I go to a budget car forum and the chart shows I should suggest a Chevy Corvette as an absolute minimum and to drive to work in a Kia Soul would be ridicules in today’s world of technology, I would have to be a fool to expect any degree satisfaction in driving a Kia Soul. But if we really take a look at what is being driven statistically and charted it based around what you get for what cost and what level of satisfaction we may have a much different chart.
I don’t want to lower the standard of excellence nor do I want to inhibit the growth of technology I want just the opposite for both. As mentioned the market place and the manufactures and free enterprise will decide for us in the long run. But the consumer also has to be factored in and their job is going to be to drive the price down. Once 4k takes hold as mentioned all the goodies will stop showing up in 1080. Then there will be a rush of those that can afford it to do so. Once a market is saturated would you rather sell a 100 $10k projectors or 100-million $1k projectors. Trust me that plan is in place already.
You have totally lost me, you seem to have a completely unique way of reading those charts. Those charts first appeared when 1080p was new and people were saying "you don't need 1080p, people can't see the difference", well the charts were intended to help people visualize where 1080p would become valuable, they were later updated with 4k resolutions for the same purpose. But again, they say nothing about minimum acceptable resolution, or minimum viewing distance. They do not say that you have to have a certain resolution to have a good image at a certain seating distance. What they do say is for a given size/distance, what resolution is likely to provide value. For example that for those who sit 15' from a 60" flat panel, 4K is not likely to provide much value.
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post #26 of 128 Old 04-06-2016, 07:51 AM - Thread Starter
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Bud,

I've been reading this and other threads on this topic, and appreciate your efforts here.

Without repeating all the technical aspects, what is the bottom line, take-home, real-world implications of what you're trying to communicate? What are the implications for someone's decision making with regard to source resolution, screen size, and seating distance?

I'm running into a "can't see the forest for the trees" type of confusion here, being inundated by all the details and technical discussion, which is preventing me from seeing the 'big picture' (pardon the pun!).
Hi Don
I’m like you in regards to my complete understanding of the topic. There is science to all things and then there is real world intuitive feel. What I am mainly trying to resolve is why the two don’t more closely align. I think with hashing this around here I’m beginning to understand better.

Coming from photography and I know that’s your business so I will make a photographic analogy for you. You are taking a photo and you adjust your camera to a sharp focus on the object of interest and you can take the photo and stuff in the foreground and background will be out of focus based on the lens and aperture used. You know you have some wiggle room around perfect focus and can employ what we call depth of field. You can shift the out of focus area more to the foreground or more to the background as a composition tool. In doing so you know there is only one point of perfect focus but like a carpenters level the bubble can move a little and as long as it’s between the lines it is good enough. Same with focus on a camera and depth of field and I feel it also holds true for projection and seating distance.

The reason is all things in reality have a good enough point and when the change is clustered around that perfect point sometimes a big jump in one factor has a tiny result in the other. If you go to the eye doctor and they tell you that you have 20/20 vision they send you home with no glasses. You go back the next year and test 20/20.5 and there is still no reason for glasses. The next year 20/21 and the eye doctor say’s you know if this keeps up in five years you will be needing glasses. You are no longer perfect but you are good enough.

I think these charts reflect something much closer than good enough, even much closer than very good and most of the world not paying any attention to them is confirming that.

You can go thru the forum and on the first page alone you will find a dozen threads where someone is recommending or stating from first-hand experience numbers closer to the amended numbers I show on the chart in the first post. Even the AVS sales people often relate seating distances twice the distances shown on the chart and assure people they won’t see screen door effect (SDE). Antidotal evidence is used all the time with the <3k projectors and these charts are used to explain the benefits to the >3k projectors.

I wanted to keep the reply short but I guess that’s going to happen. In closing I had an interesting thought last night we went out to dinner at a local sports bar and they had flat screens all over the place I was looking at a 42” 1080 TV playing HD signal from between 30 to 40 foot away. I will let you do the math but I’m sure each pixel was smaller than 1/300 of one degree of my vision, someone correct me if I’m wrong. The image on the screen didn’t look life like in any way it just looked like a flat bright flat screen across a large room. We came home and I fired up the projector and we watched a BD disk played on a Sony player downscaled from 1080 to 720 on a WXGA projector set to 720 the screen size at 16:9 would be 110” the seating distance was about 2X SH or 9 to 10 foot, I sat back and settled in on not watching details but became engaged in the movie and let my eyes take it all in and feed my brain this image mixed in with wonderful clear 5.1 sounds, and I will stop short of saying it resembled real life but it was amazing to put it mildly as if I was looking thru an open window that almost entirely filled my vision. Could it be better? I’m sure it could somehow, but at no time did I desire more. I know people will tell me my feelings are based around not knowing what I’m missing. I have viewed a lot of FP over the years and we have some new theaters in the area showing some really good digital images. I feel I’m on par with those mostly as I have an edge on foot lamberts and room treatment and ambient control.
I can’t say the simple answer use my chart numbers as they are suggestions on unknown antidotal evidence and my own perception. But after you have your theater up and running decide for yourself and come back and let us know.

Bud
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So I'm 11 feet from my 50" plasma, I have tended to rip files at 720p to watch via Apple TV ( partly coz I always have with older Apple TVs ) due to file size and limitations on old hardware. Subjective I know, but technically would I see any benefit with 1080p rips ?

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post #28 of 128 Old 04-06-2016, 08:30 AM
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Bud,

Thanks for the detailed reply. Actually, Photography is a secondary passion; my day job is as an Ophthalmologist - so I'm quite visually oriented in general!

I understand the analogy concerning focus and depth of field, and see how that can be useful in trying to understand the projector experience.

But I still need an 'overview' in terms of what you're saying with regard to sources resolution, screen size, and seating distance.

Let's just use a 120" screen as an example. The original chart implies that one needs to be seated a little closer than 15' in order to start to appreciate the benefit of having the higher resolution 4K source image. Your adjustment suggests that one needs to be a little closer than half that, or 7.5 feet, in order to start seeing the benefit.

If I'm understanding this correctly (and I'm by no means certain that I am!), you're saying that if one has a 120" screen, and sits at just under 15', then the person is not going to be able to appreciate the higher resolution of the 4K image, and presumably they are spending money on something that is not going to improve their viewing experience (let's ignore HDR for the sake of this discussion), or they need to sit twice as close to get that improvement.

By the same token, your numbers suggest that if one does sit at just under 15' from the screen, one would need a screen size of 145" to even get close to the full benefit of a 720p image, so that a much larger screen would be needed at that distance to even begin to gain the benefit of 1080p, let alone a 4K image.

Or am I completely missing the point you're trying to make, and am misinterpreting the chart, and your adjustment?

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Originally Posted by stanger89 View Post
That's the problem you have it backwards, the charts are just general guidelines, they are not definitive boundaries.
The wording of the chart can be read a lot of ways you are correct your way is a better way to look at it. I know most people don’t use the chart in that manner ether seeking information for themselves or trying to convince someone else about their project or opinion.

If confronted with the chart most people do one of two things as there is to axis to the chart. They want a 120” screen they know they can afford a 1080 projector so they go up to the line marked “full benefits of 1080p visible” run across and say I need to sit back 16’ or greater. Anything closer it is assumed they will lose PQ because the size of the pixel based around vision acuity is being compromised. After all once a benefit is reached there has to be a next thing. The amount of compromise is not known but intuitively we know when the benefits of the next thing take over the last thing is out of its range.

The second method the chart is used is I know my room and I can sit back 10’ from a screen I also know I can only afford 1080 projector. I read across to the line and see 76” is the screen size where I cross over into 4k benefits and likewise assume if 4k benefits happen the lesser resolution would be unacceptable by some amount and again we don’t know the amount.

It might be counter intuitive to try and relate to someone that benefits of 4k start here but the benefits of 1080 keep on going past the line that says “full benefits of 1080P visible” that is explained at the top on the viewing distance axis that they all look the same from this far away.

Most people do want to know when a higher resolution starts to benefit. But more want to know when a given resolution starts to hinder. It is always about going bigger. I am told all the time and the chart is used all the time to inform me that there is no way 720P should be used on a 110” screen as the pixel size will be visible and the benefits of 1080p will abound and as reinforcement of the argument the chart is shown.

Bud
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post #30 of 128 Old 04-06-2016, 08:58 AM
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My boss always says, "A good wine is one that you enjoy drinking."

Do some people feel like they can see the increased pixels with 4K and that makes the image "better" to them? Yes, so good for them.

Do some people feel like pixel count isn't as important as color saturation, deep blacks, etc.? Yes, and that's okay too.

I personally have found that what's most important to me is the horizontal viewing width (i.e. how much the image fills the width of my vision), overall image brightness, and up-and-coming things like HDR and WCG.

We sit at varying distances from 9 to 12 feet away from our TV in our living room. Until recently, we had a 42" Panasonic plasma and EVERY SINGLE TIME I watched it in the last couple of years I yearned for a larger display. Not more pixels, but just a bigger image to fill my field of view. But I also knew that HDR and WCG is the next big thing in the industry, so I knew that if I was going to go big, I also needed to be ready for the new tech coming out.

We ended up buying a 65" Samsung JS8500 and I really couldn't be happier from a cost/performance standpoint. We got a much larger image, a *brighter* overall image, HDR/WCG compatibility, and more for a great price. I'm seeing things in movies that I'd never seen before. Some thing in the background. Some little facial tic on a character. I think the increased size of the image has helped facilitate that.

Notice, that I didn't say 4K. Yes, it is a UHD TV, but that wasn't anywhere close to a driving factor for my purchase. Can I see the extra detail when watching 4K content? Maybe ever so slightly.

I just see this whole discussion about whether individual pixels are visible from what distance and charts showing optimal resolution for which screen size as a red herring. In the end, I think the most important thing is getting a good, sharp, QUALITY image that fills the field of view that you want for a price you're willing to pay. If you can get that, then good for you!
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Striving to live life in high dynamic range and ultra high definition.
Samsung UN65JS8500 / Denon AVR-X4000 / 5.1 w/ Mixed Speakers / Oppo UDP-203 / TiVo Premiere XL / Apple TV (3rd gen) / Fire TV (1st gen) / Xbox 360 R2-D2 Edition
KC area / Father of 4 / Husband / Video Producer / Skeptic

Last edited by CosmoNut; 04-06-2016 at 09:02 AM.
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