What screen size is the "sweet spot" for 1080p material? - AVS Forum
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post #1 of 38 Old 10-24-2008, 08:39 AM - Thread Starter
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I don't know if I will be able to explain this right. At what point do you start to get a softer picture with large screen? I mean, bigger is better, but say you have a 80" screen and a 120" screen side by side off identical projectors. Will the 120" look noticeably softer? At what point do you get deminishing returns? Same for small sizes, at what point do you get full benefit of 1080p? 42", 46", 50"? I know distance from the display matters, just assume optimal distance.

Like 46"-90"? 50"-100"? 50"-80"? Anything beyond 60"?
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post #2 of 38 Old 10-24-2008, 08:43 AM
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Remember there will be a different sweetspot for

1080P 8bit 4:2:0

and

1080P 12bit 4:4:4

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post #3 of 38 Old 10-24-2008, 11:15 AM
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post #4 of 38 Old 10-24-2008, 11:37 AM
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It's viewing distance not screen size that really matters. 1.5 screen widths away seems to be the optimal distance.
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post #5 of 38 Old 10-24-2008, 11:39 AM
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Theoretically, if you have 20/20 vision, things should start to look softer and/or more jagged once you cross the dotted lines for the various resolutions:


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post #6 of 38 Old 10-24-2008, 11:52 AM - Thread Starter
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So your saying a 50" at it's optimal distance will look the same as an 120" at optimal distance? I've never used a front projector setup, but I have a hard time believing an image blown up to 120" looks as sharp as an 60-80" image. There's has to be a point of diminishing returns. You can only strech the signal so much and you can only fit so much info into each pixel.

I can stand far enough away from any display to make it look "nice". That's not what I'm looking for.
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post #7 of 38 Old 10-24-2008, 12:02 PM
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I'm not quite sure I follow your question. For a 1080x1920 image should look equally sharp with a 50" screen at about 7' as it does on a 120" screen at 16'. Essentially, what it boils down to is viewing angle. There is a sweet spot around 30°. The further you are away from the display, the larger it needs to be to maintain that same viewing angle.

Here are a couple sources with more detail:
http://myhometheater.homestead.com/v...alculator.html
http://www.carltonbale.com/2006/11/1080p-does-matter/

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post #8 of 38 Old 10-24-2008, 12:17 PM
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Quote:
Originally Posted by Blacklac View Post

So your saying a 50" at it's optimal distance will look the same as an 120" at optimal distance?

I don't think the data for the chart directly addresses any issues of decreasing dpi (as you zoom the picture larger and larger). What the chart does address is that the natural acuity loss for human eyes at increasing distances will make the image look "softer", anyway, whether it is an image projected to a 100", at 40 dpi or 400 dpi (numbers just pulled out of the air to illustrate the concept).

It won't look "the same" over 2 distance scenarios, per se, but it won't necessarily look any better at the longer distance, either, even if you had unlimited image resolution at your disposal. The eyes just won't pick it up at such long distances.

Now there could be the possibility of finagling these limitations a bit, if one could arbitrarily boost high-frequency components of the image as you project to larger screen sizes. Then the dpi condition might make an appreciable difference (gives more data for the HF boost to work on, at the least). It won't look "right" or natural at closer distances. However, the natural eyesight losses at greater distances will filter down what is being projected (in a complementary manner), such that the end result could be greater in performance than could be achieved using just the classic distance/screen size alignments. I don't know what that would look like, but maybe it could be described as "greater than human vision" detail experience? Maybe that in of itself could be deemed "unnatural", or it could be amazing. I dunno!

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post #9 of 38 Old 10-24-2008, 12:35 PM
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Originally Posted by Mr. Hanky View Post

I don't think the data for the chart directly addresses any issues of decreasing dpi (as you zoom the picture larger and larger).

Perhaps I'm still not following what the OP is looking for. If you're talking about DPI on the screen (or pixels per inch), how it "looks" will be completely dependant on the distance you are viewing it from. Assuming you have 20/20 vision (or are corrected to it), and can therefore properly focus the image onto your retina over the range of distances you are concerned about, the "size" of the image on your retina will be exactly the same regardless of screen size as long as you follow the lines on the chart. The image doesn't degrade in quality due to making it bigger. It's exactly the same image, just at a larger scale. The image appears to degrade in quality due to our perception of the image. All other things being equal, screen size and viewing distance are the two variables that can be changed inversely to maintain a constant perception of equal quality.

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post #10 of 38 Old 10-24-2008, 12:38 PM
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Quote:
Originally Posted by Blacklac View Post

So your saying a 50" at it's optimal distance will look the same as an 120" at optimal distance? I've never used a front projector setup, but I have a hard time believing an image blown up to 120" looks as sharp as an 60-80" image. There's has to be a point of diminishing returns. You can only strech the signal so much and you can only fit so much info into each pixel.

I can stand far enough away from any display to make it look "nice". That's not what I'm looking for.

What resolution is IMAX? They look pretty sharp to me and it's a pretty large screen
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post #11 of 38 Old 10-24-2008, 12:48 PM
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I think the point that you don't see a difference is about 30". The bigger you get, the softer the image.

94" at 8 feet for me at 720p is still not clear as day. If I drop the size down to about 60-70 (equivalent to 1080p), it still could use some help.

The biggest question though is not at what size, but at what viewing angle... and difference in individual eyesight.

So the op who said distance is the key is half right. It is the ratio of viewing angle and distance as well as some other factors added in.

Some factors (not all)
resolution
source
display device
distance
angle
eyesight
how many beers I have had
how many beer you have had
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post #12 of 38 Old 10-24-2008, 01:58 PM
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Quote:
Originally Posted by Darin View Post

Perhaps I'm still not following what the OP is looking for. If you're talking about DPI on the screen (or pixels per inch), how it "looks" will be completely dependant on the distance you are viewing it from.

Distance and screen size are only 2 things that will effect what you see, not the only things. It is true, that after a certain threshold (as indicated by the chart), then they will be the most dominant factors. Prior to that threshold, dpi will have some contribution to the overall look, as well. You could have a mere 480p on a smaller screen, and it will seem "sharp" because the detail is all squeezed together. Then if you blow it up on a larger screen, but still below the distance/screen threshold, it won't quite "look" the same, because now that detail is spread out over a greater canvas. Quantitatively, you may be able to pick out "tinier" entities when it is blown up on a large screen (which is akin to the process of seeing more detail), but it still doesn't necessarily "look" the same in terms of perceived sharpness. What this is demonstrating is a certain "spectral relationship" of edges and textures of entities that is native to a particular image, as opposed to resolving distinct visual elements.

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post #13 of 38 Old 10-24-2008, 02:04 PM
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Quote:
Originally Posted by Mr. Hanky View Post

You could have a mere 480p on a smaller screen, and it will seem "sharp" because the detail is all squeezed together. Then if you blow it up on a larger screen, but still below the distance/screen threshold, it won't quite "look" the same, because now that detail is spread out over a greater canvas.

Of course, if you don't change the viewing distance in proportion to the change of screen size, then the apparent sharpness will change. But if you change distance in proportion to screen size (follow the lines in the chart), the apparent sharpness will be the same. It doesn't matter how much canvas you spread it over, what matters is the canvas size relative to your viewing distance. Just like you say 480p can look sharp on a smaller screen, 480p can look sharp on a bigger screen from a longer distance.

EDIT: another thing to remember... the dotted lines on the chart represent visual acuity for 20/20 vision. Speaking in rough terms, if you go left of that line, then there can be more detail in the image than your eyes can resolve. If you go right of that line, then you can resolve more detail than the image can hold. So if you are left of that line, getting closer to the image (or enlarging the image) will let you see realize more detail (assuming the content is taking full advantage of the resolution). If you are right of it, reducing the image size, or getting farther from it, will increase apparent sharpness. I'm not sure I'd consider it a "threshold", just more of an indicator of where the limiting factor is, and how limited you are. But again, your ability to resolve detail is just one part of the puzzle. There are also viewing angles that are considered to be more ideal, due to ergonomics, how we perceive size, etc. "Optimum" will vary a bit by who you ask (THX has a slightly different idea that the SMPTE, for example), but they are in a similar ballpark, and it just so happens that it corresponds closely to how our visual acuity relates to pixel pitch @ 1080p.

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post #14 of 38 Old 10-24-2008, 02:17 PM
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The OP would be better off asking in one of the display threads.
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post #15 of 38 Old 10-24-2008, 02:24 PM
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Quote:
Originally Posted by Darin View Post

Just like you say 480p can look sharp on a smaller screen, 480p can look sharp on a bigger screen from a longer distance.

I don't know how well that holds up in real use, and that is why I suspect there is more going on than simple lines on a chart. Back in "the day" when 480 (sd) was the only thing available, there was a marked difference in the "look" between, say a 50" tv and a sub 30" tv. Certainly, the 50" had a bigger, engrossing image aspect to it, but there was no disputing that images appeared "soft" compared to the same image that would appear on a 27" tv, regardless of how far or close you viewed it. You could very well make out small objects far more readily on the 50" than the 27" (as you would expect for being able to spread x amount of visual data over a larger canvas). It still didn't "look" the same. In that respect, "detail" and "sharpness" are decidedly different qualities to the experience.

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post #16 of 38 Old 10-24-2008, 02:57 PM
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Quote:
Originally Posted by Mr. Hanky View Post

I don't know how well that holds up in real use, and that is why I suspect there is more going on than simple lines on a chart. Back in "the day" when 480 (sd) was the only thing available, there was a marked difference in the "look" between, say a 50" tv and a sub 30" tv. Certainly, the 50" had a bigger, engrossing image aspect to it, but there was no disputing that images appeared "soft" compared to the same image that would appear on a 27" tv, regardless of how far or close you viewed it. You could very well make out small objects far more readily on the 50" than the 27" (as you would expect for being able to spread x amount of visual data over a larger canvas). It still didn't "look" the same. In that respect, "detail" and "sharpness" are decidedly different qualities to the experience.

I believe it is true to an extent. I sometimes think my 480p version of the Last Starfighter looked better on my 27" flat tube TV than my HD DVD version on my 94" display. It is relative to the size and distance.

It is only over long distance that distortion can take place from the effects of the air and such. This is why we can take images of the stars much better with Hubble than a land based telescope as it is outside the atmostphere. But you are dealing with miles of air in this case.

I think what you are confusing is the quality of the device and not the actual display. The best case to make for this is with projectors as you can change the size without sacrificing PQ too much (there is still some distortion when you zoom in and out)

I sit about 8-10' away (depending on location) from a 720p at 94" and there is a difference. HD in this case makes it acceptable. 1080 will make it better, but I am not going to delude myself that 1080 is perfect at this size.

This is why some folks think the picture of the big screen was worse than what they saw on their normal sized sets. In most cases, it probably was as the viewing angle was so much smaller.

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post #17 of 38 Old 10-24-2008, 03:02 PM
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Quote:
Originally Posted by Mr. Hanky View Post

... there was a marked difference in the "look" between, say a 50" tv and a sub 30" tv. Certainly, the 50" had a bigger, engrossing image aspect to it, but there was no disputing that images appeared "soft" compared to the same image that would appear on a 27" tv, regardless of how far or close you viewed it. You could very well make out small objects far more readily on the 50" than the 27"

IF the two sets are of the exact same quality, then that wouldn't hold up. The 30" and the 50" should look exactly the same, assuming you adjust your viewing distance such that they each consume the same amount of your field of view (that, in essence, is what the diagonal lines on the chart represent).

Look at it this way. Imagine a poster comprised of a given amount of solid colored squares (pixels). We'll say a grid of 1080x1920 squares. Now we take a picture of that poster with a camera, from a distance that makes the poster exactly consume the entire viewfinder. Next, we have an identical poster, except it is twice the size (same number of pixels, they are just twice as big). Now we move the camera back to a dsitance where the larger image still exactly consumes the entire viewfinder. The two captures of the poser will contain the exact same amount of detail, and will have the same apparent sharpness.

I'm not saying past experiences with various size displays are invalid. But if the apparent sharpness was different when viewing distance was scalled proportionately, then the displays themselves did not have equal image quality.

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post #18 of 38 Old 10-24-2008, 03:08 PM
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Quote:
Originally Posted by Mr. Hanky View Post

I don't know how well that holds up in real use, and that is why I suspect there is more going on than simple lines on a chart. Back in "the day" when 480 (sd) was the only thing available, there was a marked difference in the "look" between, say a 50" tv and a sub 30" tv. Certainly, the 50" had a bigger, engrossing image aspect to it, but there was no disputing that images appeared "soft" compared to the same image that would appear on a 27" tv, regardless of how far or close you viewed it. You could very well make out small objects far more readily on the 50" than the 27" (as you would expect for being able to spread x amount of visual data over a larger canvas). It still didn't "look" the same. In that respect, "detail" and "sharpness" are decidedly different qualities to the experience.

Remember though, you are also talking about different display technologies. 50" in SD days would be a rear projection set so you open up another can of worms as far as focusing, convergence, screen material. Brightness and contrast play a role as well. Remember, that chart is based purely on math and an "all other things being equal" so it works very well in the ranges where similar display technologies reign, but starts to break down as you cross the boundaries from direct view to projection (both front and rear).

That said, the chart is a good starting point. You would basically not want to not cross the line for the resolution you are shooting for, but at the same time not make the screen so big that you would start requiring the next resolution up (in this case 1440p). The rest basically centers around the display technology and making sure the contrast, brightness, color reproduction, and everything else that are more or less independent of size.
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post #19 of 38 Old 10-24-2008, 03:08 PM
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Originally Posted by bjmarchini View Post

The best case to make for this is with projectors as you can change the size without sacrificing PQ too much (there is still some distortion when you zoom in and out)

Yes, this may be the easiest comparison. But to be perfect, not only do you need a lens of high enough quality that it isn't introducing noticeable distortion, you also need a light source that scales it's output as you zoom the image larger.

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post #20 of 38 Old 10-24-2008, 03:35 PM
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Originally Posted by bull3964 View Post

That said, the chart is a good starting point.

I think that is the important point we all need to remember. The chart is a starting point, not an almighty testament of what you will/will not see, that must be defended to the death. If all factors were incorporated into a chart that defines what you will/will not see, it would end up being useless to most people because nobody could understand it. In the real world, all things are not perfectly equal, things are not aligned perfectly according to a line on a chart, and devices are not performing at theoretical spec. Hence, there are more possibilities that are possible than what is distinctly implied by a simple chart.

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post #21 of 38 Old 10-24-2008, 03:52 PM
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Quote:
Originally Posted by Mr. Hanky View Post

The chart is a starting point, not an almighty testament of what you will/will not see

There is a certain amount of truth to that, in that we don't all have the same visual acuity. We may each have our own individual lines. But the fact remains that if you view two different images identical in every respect EXEPT for size, and you vary your distance such that the that they each consume the exact same amount of your field of vision, they will have the same apparent sharpness. That is simple optics. Yes, there are factors that can distort the results (such as the air example given earlier), but for the distances being discussed here, there would be no discernable difference ASSUMING you don't hit any eyesight limits (such as being outside of your focus range).

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post #22 of 38 Old 10-24-2008, 04:15 PM
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Ok, now try that with a computer monitor, once at a lower resolution, and then at the native resolution. Keep the same distance (fill your field of view). I don't think you will find anybody who will say the 480 setting and the 1024 setting look identical. Even considering the "native resolution" effect on a fixed pixel display, there's no way you will get the 480 setting to look identical to the 1024 setting. There's a fundamental difference in dpi...and we are also working at a viewing distance that is below the threshold lines indicated on the distance/viewing size chart. That was the original context of my remarks (and I explicitly stated so). I also was clear to specify that beyond the threshold line, the viewing distance and screen size would be the dominant factors.

Several times I have been replied to as if I was refuting the implications of the chart, when I was not. What I have been saying is that dpi does enter into the experience in scenarios below the threshold line. That is not introducing anything contrary to the chart, hence people should not interpret my comments as such.

Granted, for hdtv applications, most people will be exploring configurations very proximal to the threshold lines not only out of guidance, but also out of practicality. Viewing in a configuration that is below the threshold line will definitely challenge the realms of practicality, but it isn't impossible.

By all means, if your viewing situation is aligned to be right on the threshold line or beyond (out of spacing practicality), then you should not expect any performance aspects beyond what is indicated by the chart.

...and let's clarify one little detail about the chart. The lines are not rigidly based on what size "fills your field of view". If you pick a display size and really get up close to where it really fills your field of view, it won't necessarily land on any of those threshold lines. It might at the high end of the size range, but definitely not on the low and mid of the size range. So potentially there could be more possibilities in real use, than people have been implying just by following the threshold lines directly. If you really fill your field of view in the lower half of the size range, you will probably end up at hypothetical threshold lines for resolutions appreciably beyond the customary 1080p of hi-def standards.

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post #23 of 38 Old 10-24-2008, 04:29 PM
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Computer monitors aren't a good example because, as you noted, they are fixed pixel displays. You can't scale the image aware from their native resolution without distorting it. I'm not intending on putting words in your mouth as to the validity of the chart. It is what it is. The OP asked: "at what point do you get full benefit of 1080p? 42", 46", 50"" And the answer is: it depends on your viewing distance. That is exactly what that chart answers, and why it was created.

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post #24 of 38 Old 10-24-2008, 04:54 PM
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My remarks actually remain in good faith with the charts, though. If we take the oft repeated criteria of "filling your field of view" for a given display size, you will be at such a distance whereby greater resolution (and hence dpi) will yield visual benefits (since we are then operating at a regime that is below the supplied threshold lines for typical resolutions). This will probably be the case at the more reasonable/practical display sizes, probably not so much at the very large display sizes where distance acuity properties will dominate.

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post #25 of 38 Old 10-24-2008, 06:11 PM
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Quote:
Originally Posted by Mr. Hanky View Post

If we take the oft repeated criteria of "filling your field of view" for a given display size, you will be at such a distance whereby greater resolution (and hence dpi) will yield visual benefits

Just to clarify so I'm not leading anyone astray, my earlier comments to field of view were not inteded to be a suggestion that a proper distance results in "filling your field of view". The intent was to communicate comparisons of screen size and viewing distances such that the screen consumes the same amount of field of view at various screen sizes. The intent really is to maintain the same viewing angle. Filling the field of view for both sizes being compared would indeed result in the same viewing angle being constant, and make the comparison valid. But our field of view is almost 180°... that would probalby result in too short of a distance for comfortable viewing. Closer to 30° is a more common recomendation for a home theater screen viewing angle.

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post #26 of 38 Old 10-24-2008, 10:50 PM
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Originally Posted by Mr. Hanky View Post

Ok, now try that with a computer monitor, once at a lower resolution, and then at the native resolution. Keep the same distance (fill your field of view). I don't think you will find anybody who will say the 480 setting and the 1024 setting look identical. Even considering the "native resolution" effect on a fixed pixel display, there's no way you will get the 480 setting to look identical to the 1024 setting. There's a fundamental difference in dpi...and we are also working at a viewing distance that is below the threshold lines indicated on the distance/viewing size chart. That was the original context of my remarks (and I explicitly stated so). I also was clear to specify that beyond the threshold line, the viewing distance and screen size would be the dominant factors.

Several times I have been replied to as if I was refuting the implications of the chart, when I was not. What I have been saying is that dpi does enter into the experience in scenarios below the threshold line. That is not introducing anything contrary to the chart, hence people should not interpret my comments as such.

Granted, for hdtv applications, most people will be exploring configurations very proximal to the threshold lines not only out of guidance, but also out of practicality. Viewing in a configuration that is below the threshold line will definitely challenge the realms of practicality, but it isn't impossible.

By all means, if your viewing situation is aligned to be right on the threshold line or beyond (out of spacing practicality), then you should not expect any performance aspects beyond what is indicated by the chart.

...and let's clarify one little detail about the chart. The lines are not rigidly based on what size "fills your field of view". If you pick a display size and really get up close to where it really fills your field of view, it won't necessarily land on any of those threshold lines. It might at the high end of the size range, but definitely not on the low and mid of the size range. So potentially there could be more possibilities in real use, than people have been implying just by following the threshold lines directly. If you really fill your field of view in the lower half of the size range, you will probably end up at hypothetical threshold lines for resolutions appreciably beyond the customary 1080p of hi-def standards.

Of course they wouldn't. If I take my CRT and put it CD (Crappy Definition) instead of its native 1280x1024, it is spreading lines over pixels. This is a terrible argument. Sorry but its true. Not only does common sense dictate what most of us are saying, but the laws of physics as well.

The bottome line IS the viewing angle.

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post #27 of 38 Old 10-24-2008, 11:54 PM
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Certainly, there are peripheral effects involved which make it a less than ideal comparison, however, that in of itself doesn't discredit the relevance (it's not like monitors become utterly incapable of reproducing material outside of the native resolution; 480 is sufficiently far away from and lower than 1024 such that there is very little reason to expect that representative 480 performance is implausible). The bottom line is that if you have maxed out your "viewing angle", then you shouldn't see a difference between a lower and higher resolution setting. However, we know from common experience that there IS a difference. So that should suggest that viewing angle isn't necessarily the only factor at work under all conditions. It's still a pretty safe factor to run with for most circumstances. That, I wouldn't argue.

Things become even less "exact" once we come to acknowledge that even a "standard" viewing angle or field of view criteria are not necessarily confined to hard, concrete numbers.

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post #28 of 38 Old 10-25-2008, 05:17 AM
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Quote:
Originally Posted by bjmarchini View Post

If I take my CRT and put it CD (Crappy Definition) instead of its native 1280x1024, it is spreading lines over pixels. This is a terrible argument.

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Originally Posted by Mr. Hanky View Post

Certainly, there are peripheral effects involved which make it a less than ideal comparison, however, that in of itself doesn't discredit the relevance

But the fact that you DO get different results DOES discredit the relevance. Again, it's simple optics. If you take out those factors that cause the images to be different IN ANY WAY beyond their scale, there is no reason that can be explained by the laws of physics that would cause there to be any discernable difference at reasonable distances as long as there are no specific vision problems playing a factor. If you don't believe me, take a relatively low resolution photo, take it to a professional printer, and ask them to blow it up to two different poster sizes using absolutely no interpolation. Then view them at different distances to keep the viewing angle constant. It's still not a perfect comparison because the printer will have a fixed printing resolution that will allow more dpi per photo pixel in the larger print, but using a low rez photo should reduce that factor. It may also be difficult to ensure that interpolation isn't being used, since that is usually desireable. The FP with optical zoom comparison is also a good one to use, keeping in mind the light output handicap for the larger zoom. Or heck, just go to a store that has a 60" and 73" Mitsubishi RPTV of the same series (like wd-60735 vs. wd73735). The smaller one will have a brighter picture since they use the same bulb, but if they have the same settings, the PQ should be the same when viewed at appropriate distances to keep viewing angle the same.

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post #29 of 38 Old 10-25-2008, 11:58 AM
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Just sit 1.5 screen widths away and you'll be happy.
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post #30 of 38 Old 10-25-2008, 12:27 PM
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Yes, the general rule of thumb for high-def television watching is to sit between 1.5 and 1.75 times the diagonal screen size (it will vary somewhat to taste). Given a good-quality HD television, a good-quality source, and a direct-viewing angle, these numbers should apply.

But it's not just limited to television watching. Sit in the front row of a motion-picture theater, where the picture you're seeing should be the best-possible quality (assuming a good, undamaged print, something rare these days), and you'll see a good deal of blur and natural film grain. Sit progressively farther back in the theater, and the picture should begin to sharpen and clear up. As several people here pointed out, it's simple optics.

But just as some people prefer to sit in the front row or the back row of a movie theater, so do some people prefer to sit closer or farther away from their TVs at home. (I sit 65" from a 40" TV screen, and I'm happy as a clam. Most friends of my acquaintance sit much farther away from their screens, often 8-10 feet [96"-120"] from 40"-50" screens, and they're happy, too. To each his own.)

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