I've got a modest technical background, so I tend to apply critical thinking and basic physics to most things I read or hear. I see a growing number of people who claim to be able to see SDE on modern 768P plasmas at absolutely absurd distances, so I decided to use the little bit of knowledge I have regarding optics as a litmus test of the validity of such claims. Besides, sometimes my day job in the aerospace industry involves more paper pushing and email composing rather than actual "number crunching" engineering. So once in a while I'll whip up a quick spreadsheet just to give me a sense of technical accomplishment. So I guess it's not all motivated by proving some "naysayers" wrong... well... maybe 99% of it is if I had to quantify it, the other 1% can be the fuzzy accomplishment thing. :D

So I took a screenshot of a really quick .xls sheet I made. Excuse the formatting, it was done quickly. Besides, I'm an engineer, not an artist!

http://img263.imageshack.us/img263/6262/angularresolutionum7.jpg

The key points are highlighted in yellow. At the BEST CASE diameter for the apeture of a human eye(very dark room), and at the BEST CASE wavelength of light being emitted by the surrounding pixels(violet, borderline ultraviolet), you physically CANNOT see the SDE grid of a plasma over about 6 ft. The "target width" SDE measurement was also on the highside of 5 measurements I made of the SDE grid of my 50" 768P plasma. Change the wavelength of light to 700 nm, or a dark red, and you get a distance of only 3.5 ft with everything else beign best case.

Now keep in mind this isn't the distance that people should be able to see the grid, as this is the UPPER LIMIT as defined by optical physics. I don't care how good your vision is, you will never ever exceed this limit with anywhere near normal sized eyes. Beyond this distance, the diffraction of the light waves will make this sized object impossible to distinctly resolve.

Using typical visual accuity data for humans, the average distance is much much closer than this upper limit. Yet everybody on this forum seems to self proclaim an absolutely amazing visual accuity that is probably in the upper 0.00001% of the population, so I figured I'd go with the absolute physical limits. :rolleyes:



So as you can see, some people like this (http://www.avsforum.com/avs-vb/showthread.php?p=10331960&&#post10331960) really must have a separate set of physical laws apply to them to have such superhuman vision.




I think I'm just really excited to be getting my 58PX600U tomorrow! :D

Interesting post. :)
I think the display also will differ.
I see SDE if I get real close (>3') on my 50Px500u.
It's funny because with most other plasma's, I can see it from 4-6'.
Go figure...

Great post.

Now wait for somebody to say, "I don't care what the science says, I can see SDE at 20 ft. on a 50 inch plasma."

Great post.

Now wait for somebody to say, "I don't care what the science says, I can see SDE at 20 ft. on a 50 inch plasma."

The OP already posted an example and it's not the most outrageous I've seen on AVS. ;)
There are some Supermen here on AVS. :D

Interesting post. :)
I think the display also will differ.
I see SDE if I get real close (>3') on my 50Px500u.
It's funny because with most other plasma's, I can see it from 4-6'.
Go figure...


It'll definitely differ with the display. I figured the Vizio thing would pretty much mean it's a worst case there as well. :D

Interestingly enough, the maximum physical distance will also vary with what colors the surrounding pixels are. I have noticed it is easier to pick out SDE on a blue/green screen vs. red. This might be down to the varying sensitivity of our eyes to certain wavelengths, but maybe this physics thing really does have more influence than we give it credit for based on all the emperical/rule of thumb data we use for eyesight.

The measurement isn't a set in stone thing either, as I'm not sure what the actual grid structure width is on my (soon to be gone) Vizio is. It was just me after 2 beers grabbing some calipers and getting a crazy idea to prove some AVS supermen wrong.

I personally don't see SDE on my current set after about 3-4' away on most material. Might pick up hints of it at about 4.5', but past that I can't pick it out.

I see a growing number of people who claim to be able to see SDE on modern 768P plasmas at absolutely absurd distances

At the BEST CASE diameter for the apeture of a human eye(very dark room), and at the BEST CASE wavelength of light being emitted by the surrounding pixels(violet, borderline ultraviolet), you physically CANNOT see the SDE grid of a plasma over about 6 ft.

The "target width" SDE measurement was also on the highside of 5 measurements I made of the SDE grid of my 50" 768P plasma. Change the wavelength of light to 700 nm, or a dark red, and you get a distance of only 3.5 ft with everything else beign best case.

Now keep in mind this isn't the distance that people should be able to see the grid, as this is the UPPER LIMIT as defined by optical physics. I don't care how good your vision is, you will never ever exceed this limit with anywhere near normal sized eyes. Beyond this distance, the diffraction of the light waves will make this sized object impossible to distinctly resolve.

Using typical visual accuity data for humans, the average distance is much much closer than this upper limit. Yet everybody on this forum seems to self proclaim an absolutely amazing visual accuity that is probably in the upper 0.00001% of the population, so I figured I'd go with the absolute physical limits. :rolleyes: Make up all the charts and graphs that you want, but i absolutely positively see SDE on my 42" 768p Plasma at 7 feet. At 8 feet i have to really focus on it to see it, and at 9 feet i can no longer see it. I'm 50, i don't wear glasses, and i have normal if not small eyes, and i see SDE clearly. And on my friend's 768p 50" Panasonic i see the SDE at 9 feet. I'm probably in the minority, but i see what i see :)

Make up all the charts and graphs that you want, but i absolutely positively see SDE on my 42" 768p Plasma at 7 feet. At 8 feet i have to focus on it to see it, and at goes away at 9 feet. I'm 50, don't wear glasses, and i have normal if not small eyes, and i see SDE clearly. And on my friend's 768p 50" Panasonic i see the SDE at 9 feet. I'm probably in the minority, but i see what i see :)

You sure those shades aren't hiding some mondo 5" eyeballs in your avatar? :D


I don't know what to say other than maybe you're concentrating on the fact that the perceived brightness might go down, but you can't possibly be fully resolving the SDE grid at that distance right?

Great post.

Now wait for somebody to say, "I don't care what the science says, I can see SDE at 20 ft. on a 50 inch plasma."


I dont care what the science says, i can see SDE at 20ft on a 50in plasma, lol ok may be not 20ft on a 50in but i was looking today at some plasmas and i did see SDE on a 60 pioneer at 12ft i noticed it most when the screen showed bright white scenes

Make up all the charts and graphs that you want, but i absolutely positively see SDE on my 42" 768p Plasma at 7 feet. At 8 feet i have to really focus on it to see it, and at 9 feet i can no longer see it. I'm 50, i don't wear glasses, and i have normal if not small eyes, and i see SDE clearly. And on my friend's 768p 50" Panasonic i see the SDE at 9 feet. I'm probably in the minority, but i see what i see :)

Man, I just don't get that at all.
After about 6', it just seems impossible to see it on any 50" panel, let alone a 42"er. :eek:

Man, I just don't get that at all.
After about 6', it just seems impossible to see it on any 50" panel, let alone a 42"er. :eek:Well you're looking at it through your own eyes. I wish there were some way i could transmit my optic nerve signal to yours so you could see what i see. Seriously, i've measured it out in increments - in stores, in friend's houses, and with my own 42 incher and my threshold is 7-8 feet. Also, my former girlfriend who was a little over half my age (with young gorgeous eyes) could also see SDE at the exact same distances as i do. I showed her what it was by having her look for it at 4 feet. She backed away and could still see it at 7 feet (sitting on front edge of recliner), not so much at 8 feet (sitting upright in recliner), and not at all at 9 feet (recliner in reclined position). Same sensitivity to it as i have.

But i can also spot a mosquito flying on the other side of the room, lock on to it and visually track it while i approach it, then grab it out of thin air. I have pretty acute vision i guess :D

Perhaps not SDE but text and graphics are easy to tell apart especially on diagonal lines which show up as a staicase on lower resolution models.

if the source is sweet, who cares if there's sde--really? lol.

if you can't get past sde = don't sit so close

:p

Sure, this is what they teach you in Optics 101, and I don't disagree with these equations.

But there a few things these equations do not model:

1) Most people have not one, but two eyes.
In antenna theory, when we have two elements, the resolution is computed not from each individual element, but by the entire array.
So one would expect much higher horizontal resolution when using two eyes.

2) When there are moving objects (or your head/eye is moving), you can see much higher resolution than for static objects.
For example, using a technique called synthetic aperture radar (where a satellite is continuously making measurements as it is moving) one can see far, far more resolution than predicted from simply calculating the diffraction resolution from the aperture of the antenna.
For example, you should notice a flying football to be much more sharp than a one-eye diffraction limit chart would predict (even using just one eye).

3) The eye is a great measurer of small differences in brightness.
When a coarse resolution interacts with certain display patterns,
it can create differences in brightness that can be picked up by the eye.
Some might argue this is not resolution, but I argue absolutely it is.
After all, the diffraction pattern is not uniform across a specific angle, but sin x/x like in amplitude behavior. In fact, in the early days of radar, people realized that they could get much, much better than the diffraction limit by looking at variations in amplitude. This can be done by either movement or by using two radar receivers (or in our case, two eyes).

4) Finally, the eye is not static. If you look under a microscope, your eye is constant jittering back and forth. This will increase resolution, for the reasons described above.


At the end of the day, experiment is the real world, theories are just trying to model that world.

So I would recommend do some experiments to verify your theory, and then iterate the theory as required! :)

Sure, this is what they teach you in Optics 101, and I don't disagree with these equations.

But there a few things these equations do not model:

1) Most people have not one, but two eyes.
In antenna theory, when we have two elements, the resolution is computed not from each individual element, but by the entire array.
So one would expect much higher horizontal resolution when using two eyes.

2) When there are moving objects (or your head/eye is moving), you can see much higher resolution than for static objects.
For example, using a technique called synthetic aperture radar (where a satellite is continuously making measurements as it is moving) one can see far, far more resolution than predicted from simply calculating the diffraction resolution from the aperture of the antenna.
For example, you should notice a flying football to be much more sharp than a one-eye diffraction limit chart would predict (even using just one eye).

3) The eye is a great measurer of small differences in brightness.
When a coarse resolution interacts with certain display patterns,
it can create differences in brightness that can be picked up by the eye.
Some might argue this is not resolution, but I argue absolutely it is.
After all, the diffraction pattern is not uniform across a specific angle, but sin x/x like in amplitude behavior. In fact, in the early days of radar, people realized that they could get much, much better than the diffraction limit by looking at variations in amplitude. This can be done by either movement or by using two radar receivers (or in our case, two eyes).

4) Finally, the eye is not static. If you look under a microscope, your eye is constant jittering back and forth. This will increase resolution, for the reasons described above.


At the end of the day, experiment is the real world, theories are just trying to model that world.

So I would recommend do some experiments to verify your theory, and then iterate the theory as required! :)

Well, if you had listened a little better in Optics 101, or taken a few college level physics courses, then you would know that none of those issues have any bearing on this equation or the results. :cool:

This is an approximation of the famous single slit experiment, and deals with the upper limit of how THE LIGHT diffracts after going through your iris. It has nothing to do with how good you think your vision is, how the resolution gets higher when you move your head, or how many eyeballs you've got looking at the set. You could have 1000 eyes at the same distance, and the light would still diffract onto itself(this is the distance out to the first diffraction wave/ring if you want to look at it that way) at that distance after passing through the opening to your eye.

Like I said, those emperical "rules of thumb" are helpful in explaining why we see the way we do, but when it comes to the upper limit of resolving a detail, this equation is very accurate.


I think some people might confuse being able to see pixel structure, which is about 5x wider than the SDE grid, with seeing SDE. You're just seeing the aliasing inherent with a fixed pixel display, which is possible on a 42" set at 8-9' with really really good eyesight and a bit of the AVS superman syndrome. :D

It would be interesting to do a blind these on this one. I bet those that claim to see the SDE when they know what the plasma is my not be so sure in a blind test. I do not see any SDE on my 50PHD7UY after about 4 feet and this is with 20-15 corrected vision.

Well, if you had listened a little better in Optics 101, or taken a few college level physics courses, then you would know that none of those issues have any bearing on this equation or the results. :cool:

This is an approximation of the famous single slit experiment, and deals with the upper limit of how THE LIGHT diffracts after going through your iris. It has nothing to do with how good you think your vision is, how the resolution gets higher when you move your head, or how many eyeballs you've got looking at the set. You could have 1000 eyes at the same distance, and the light would still diffract onto itself(this is the distance out to the first diffraction wave/ring if you want to look at it that way) at that distance after passing through the opening to your eye.

Like I said, those emperical "rules of thumb" are helpful in explaining why we see the way we do, but when it comes to the upper limit of resolving a detail, this equation is very accurate.


I think some people might confuse being able to see pixel structure, which is about 5x wider than the SDE grid, with seeing SDE. You're just seeing the aliasing inherent with a fixed pixel display, which is possible on a 42" set at 8-9' with really really good eyesight and a bit of the AVS superman syndrome. :D

I think you may be right with this last point, but I disagree that it requires a superman -- just someone who has learned what a great display looks like -- one with no visible artifacts.

I agree that the previous poster's analogies weren't directly applicable, but I do agree with one point -- the brain is the one seeing the picture, not just the eyes. The brain is a pattern processor, that works in time as well as on a static view. The ability of the brain to notice something like SDE only requires that some visual cues of it be available -- not that the pattern is readily resolvable in one static frame. If, by moving the head, and using 2 eyes, and being trained to look for the signs of SDE, the brain can notice it beyond the resolution limit, then so be it.

The problem with your resolution limit is:

1) It assumes that the contrast features created by the screen are uniform. If there is no lower spacial frequency screening there (like that you would see between pixels, as opposed to between colors).

2) The resolution limit is defined as the point where the peak of one diffraction disk hits the troph of another. At this point, there is only a small dip in intensity between the objects, and they "almost" look like one. The problem is with the "almost". They are, in fact, still resolvable as 2 things, just not easily. However, very quickly they will merge into one, but not before looking like an elongated blob still.

3) a line pattern, when masking another high-frequency pattern, can cause moire, which results in lower frequency patterns, which are easily visible. Therefore, 2 screens in front of each other can easily be visible. I don't believe that is applicable here, however, unless there is an anti-reflection screen that has lines on it.

I suggest that while resolution calculations will get you close (one certainly can't see better than twice the resolution limit, for instance), they will not get you the final solution. People may well be seeing the separation between pixels, and not the actual screen you are calculating for. Others may in fact see the finer screen.

Instead of a resolution test, what we need is a controlled SDE test. The visual system is an amazing thing, and you might find it comes up with interesting results.

However, based on your calculation, I do find it difficult to believe that at 10 feet, your fine grid will be visible. It is more likely that the grid separating pixels is what is visible.

The measurement is of the grid separating pixels. AFAIK, you can't see the wire grid on a plasma from the front of the set(yes, I realize that the grid between the pixels is probably used to carry signal wires, but that's what I measured). RGB subpixels are basically right on each other as far as I can tell from just a few inches away. No way someone is resolving those at any reasonable distance.

I do understand what you're saying about visual processing and picking up on clues, but I think it's safe to say that once you have the first diffraction ring bleeding over onto the grid, it'll be impossible to see said grid BY DEFINITION. You might see slightly varying brightness, although I doubt the claims of anybody who says they can detect this effect which is a fraction of a pixel wide at the 10+ ft some of the "claims" state.

This also isn't an indepth analysis, as this isn't my field of expertise, nor did I spend anymore than 10 minutes on it. So of course there are some rough assumptions, but I think for the purposes of illustrating an estimated distance of the diffraction pattern making the SDE grid "disappear," I think it's successful.

I understand the science that you are referring to and I'm not necessarily doubting the equations are accurate in themselves. However, for those of us who do actually see SDE beyond the chart that you specify... I'm not sure what else can be said to "prove" what we are actually seeing. I do see SDE all the way to about 8.5feet. No chart in the world can modify what my eyes are viewing! When I first started looking for TVs, I didn't even know what to call it... all I new was that dark/solid colors on the plasma tvs were sort of "gassy" and broken up just a hair by a "screen-like" view. Not horrible, but just enough to cause distraction. Now let me preface this by saying although I don't have too many posts on this board, I would definitely consider myself above average in my video tech knowledge... so I'm not just shooting from the hip here.

I did a visual test a couple of months ago with 2 pioneer tvs at one of our local high-end television stores. We set up the 50inch FHD-1 and 5070 side by side, with the same programming (SD, 720p, 1080i, and 1080p content). We even used a measuring tape to see where the differences could no longer be seen. He said he stopped seeing a difference at about 6.75 feet... however, I could still see SDE to about 8.5 feet. Trust me, I wanted to walk home with a 5070 that night, but I couldn't pull the trigger because I realized I would need a 1080p capable set. The result is that it is mid-April, and I still haven't bought a set because I'm waiting for the new 1080p sets to come out.

I'm obviously not going to change the minds of those who only look at the charts and numbers (or what they personally can see), and obviously they are not going to change my mind of what I am actually seeing. All I can do is present what my eyes are showing me. I'll add that at farther distances, I only see SDE in dark colors (such as a night scene). Also, I had Lasik Eye surgery about 4 years ago, so I am not sure if that has somehow caused my eyes to be more sensitive than others... which is a possibility because "motion blur" still drives me nuts even when my friends or family can't see it! It's simply what my eyes are showing; there's nothing else I can say...

I had Lasik 7 years ago and don't see SDE after about 4-4.5 ft on most 50" 768P plasmas, so that's not it.

Maybe I should ask for head shots for the people who can see SDE way out there. Maybe you guys all have big beady eyes. Did you ever get called owl-face in grade school or something? ;)

This also isn't an indepth analysis, as this isn't my field of expertise, nor did I spend anymore than 10 minutes on it. So of course there are some rough assumptions, but I think for the purposes of illustrating an estimated distance of the diffraction pattern making the SDE grid "disappear," I think it's successful.

Well, optics is one of my fields of expertise, though I'm not an expert in plasma TVs. In fact I'm a newbie at all flat panels, being a CRT guy so far. I think I'll have to look at those grids and try to figure out for myself what exactly people might be seeing.

Well, if you had listened a little better in Optics 101, or taken a few college level physics courses, then you would know that none of those issues have any bearing on this equation or the results. :cool:

This is an approximation of the famous single slit experiment, and deals with the upper limit of how THE LIGHT diffracts after going through your iris. It has nothing to do with how good you think your vision is, how the resolution gets higher when you move your head, or how many eyeballs you've got looking at the set. You could have 1000 eyes at the same distance, and the light would still diffract onto itself(this is the distance out to the first diffraction wave/ring if you want to look at it that way) at that distance after passing through the opening to your eye.

Like I said, those emperical "rules of thumb" are helpful in explaining why we see the way we do, but when it comes to the upper limit of resolving a detail, this equation is very accurate.


I think some people might confuse being able to see pixel structure, which is about 5x wider than the SDE grid, with seeing SDE. You're just seeing the aliasing inherent with a fixed pixel display, which is possible on a 42" set at 8-9' with really really good eyesight and a bit of the AVS superman syndrome. :D



Well, its true I am not a physicist - - I am an engineer.
When I was in grad school, I spent 5 years as a researcher developing quasi-optical systems for NASA.

Trust me, I know a little bit about resolution! :)

I am not trying to make any claims with respect to SDE measurements,
but I will say that I can make out differences between 480p vs. 720p,
or 720p vs. 1080 at distances that a simple one-eye diffraction equation would indicate are not possible.

And there are definitely reasonable engineering explanations for this.

I've got a modest technical background, so I tend to apply critical thinking and basic physics to most things I read or hear. I see a growing number of people who claim to be able to see SDE on modern 768P plasmas at absolutely absurd distances, so I decided to use the little bit of knowledge I have regarding optics as a litmus test of the validity of such claims. Besides, sometimes my day job in the aerospace industry involves more paper pushing and email composing rather than actual "number crunching" engineering. So once in a while I'll whip up a quick spreadsheet just to give me a sense of technical accomplishment. So I guess it's not all motivated by proving some "naysayers" wrong... well... maybe 99% of it is if I had to quantify it, the other 1% can be the fuzzy accomplishment thing. :D

So I took a screenshot of a really quick .xls sheet I made. Excuse the formatting, it was done quickly. Besides, I'm an engineer, not an artist!

http://img263.imageshack.us/img263/6262/angularresolutionum7.jpg

The key points are highlighted in yellow. At the BEST CASE diameter for the apeture of a human eye(very dark room), and at the BEST CASE wavelength of light being emitted by the surrounding pixels(violet, borderline ultraviolet), you physically CANNOT see the SDE grid of a plasma over about 6 ft. The "target width" SDE measurement was also on the highside of 5 measurements I made of the SDE grid of my 50" 768P plasma. Change the wavelength of light to 700 nm, or a dark red, and you get a distance of only 3.5 ft with everything else beign best case.

Now keep in mind this isn't the distance that people should be able to see the grid, as this is the UPPER LIMIT as defined by optical physics. I don't care how good your vision is, you will never ever exceed this limit with anywhere near normal sized eyes. Beyond this distance, the diffraction of the light waves will make this sized object impossible to distinctly resolve.

Using typical visual accuity data for humans, the average distance is much much closer than this upper limit. Yet everybody on this forum seems to self proclaim an absolutely amazing visual accuity that is probably in the upper 0.00001% of the population, so I figured I'd go with the absolute physical limits. :rolleyes:



So as you can see, some people like this (http://www.avsforum.com/avs-vb/showthread.php?p=10331960&&#post10331960) really must have a separate set of physical laws apply to them to have such superhuman vision.




I think I'm just really excited to be getting my 58PX600U tomorrow! :D

Dude if you're buying a 720P 58" set, you don't need to try to justify it to the whole world by starting another topic on the junk mathematics of 1080p vs 720p. I think you might be the slightest bit insecure buying such a large plasma that's 720p, but that's neither here nor there. Just be happy with your purchase and stop trying to justify it in your head (and ours). I for one CAN easily tell the difference at nominal distances between a 50" 1080p and 768p plasma, let alone a 58" or 60". And I don't have superhuman vision. Deal with your inferiority complex. :D It's the root of your post.

Dude if you're buying a 720P 58" set, you don't need to try to justify it to the whole world by starting another topic on the junk mathematics of 1080p vs 720p. I think you might be the slightest bit insecure buying such a large plasma that's 720p, but that's neither here nor there. Just be happy with your purchase and stop trying to justify it in your head (and ours). I for one CAN easily tell the difference at nominal distances between a 50" 1080p and 768p plasma, let alone a 58" or 60". And I don't have superhuman vision. Deal with your inferiority complex. :D It's the root of your post.

Inferiority complex.. haha Not quite.

I could afford a 1080P plasma if I wanted to, I just became a bit interested in some of the claims of seeing SDE on this forum so I made up a little spreadsheet.

I could likely see the difference between a 768P and 1080P 58" set at the ~12-13' I sit from the set, but I'm frankly not that concerned about the resolution thing. Some are, but I haven't been all that impressed with the 65PX600U's picture compared to Panny's more affordable 768P offerings. Technology moves so fast that I am usually happy to stay one step behind as long as I personally am happy with the purchase. Same thing with computers.. I get a cheap chip and overclock it until I get tired of it and step up a little.

Now as far as what conversation of resolution this has to do with the original thread - ABSOLUTELY NOTHING. I was talking about SDE - and only SDE. I have no idea what the grid structure is like on a 1080P set, as I've never taken a pair of calipers to one. I don't notice SDE on 1080P sets in big box stores, but I don't really notice it on 768P sets a few ft back either, so that doesn't say much.

I work with NASA people all the time, so I'm not really impressed with your name dropping. Especially after you successfully demonstrated that you either feel threatened by my off-the-cuff 10 min spreadsheet and my defense of it, or you are the forum police to tell me you don't like whatever equipment I own(doesn't bother me in the slightest).... or maybe you just have poor reading comprehension. Who knows...

My activity on the forum is what influenced me to make the post, and since I bought my set, yes, I've been spending more time here. I really have nothing to prove to anybody else about my buying decisions, and you won't see me asking a "which do you think looks better" thread. I buy what I think looks good, and makes sense to me at the time. The 58" Panny being blown out, which I always thought looked great, definitely fit that bill.


Anyway, saw this a bit late, but I thought it was ridiculous enough to warrant a response.

BTW - loving my 58PX600U's picture. Looks stellar, and the SDE grid is noticeably smaller than on my Vizio P50HDM from close distances. I'm all about trading a little bit of detail for much more size, and at the price it was simply impossible to refuse. :D