Eye resolution

[ReesR]

As I was watching the PBS special "Over Alaska" a question formed in my head...

What is the resolution of our own eyes?

As I was glued to the program I was asking myself "is my eyesight the only limiting factor now when watching high defintion programming?"

With corrective lenses my glasses give me 20/20 eyesight. But would we be able to see anything noticeably better if we saw high def in anything higher than 1080i?

Anyone have any "insights?" no pun of course.



------------------
Rees Roberts
Racine, WI
reesr@wi.net

HDTV Receiver: Sony KD-34XBR2
Bi-directional Yagi Antenna at 30 feet

[MesaV]

Here you go... More than you ever wanted to know... http://members.aol.com/MonT714/tutorial/the_eye/acuity.html

My eye sight used to be 20/15; when it dropped to 20/20 I could really notice a difference. Now, reading glasses...

[ReesR]

Thanks for the link. I, however, could not translate that info into finding out if the eye could discern any additional difference in picture quality if the resolution was higher than 1080i. So, I sent this guy an email and asked him. I will post his reply if he does get back to me.

Meanwhile, I came across this interesting link about video viewing in the future.

Interesting concept:
http://seattlepi.nwsource.com/business/27731_retina18.shtml

[MesaV]

Try this on for size:
http://newton.dep.anl.gov/askasci/comp99/CS041.htm

Question - Presently there is quite a bit of talk about pixels. Each digital camera manufacrer claims there camera has 3 million pixels, another 3.5 million, on and on. This reminds me of the 50's & 60's when Hi-Fi audio manufacturers claimed there equipment had a wider bandwidth than its competitor. So the question is what is the resolution of the human eye, and can the figure be quoted in pixels?

[Pat]

I don't have the answer to the exact question you asked, but have some related info. A guy who seemed to know what he was talking about on HomeTheaterSpot, figured out the optimal viewing distance for HDTV for sets of various sizes. Any closer, and you could see individual pixels. Any farther away, and you couldn't see everything presented.

Turns out for my 65", the distance is 8 to 9 feet. Smaller sets would be significantly closer, and larger ones would be slightly farther away. (Sorry, can't remember any other sizes, but it's no doubt proportional to the area of the screen.)

The fact is, almost nobody sits close enough to discern all the detail presented.

[MesaV]

Here it is: http://www.myhometheater.homestead.com/viewingdistancecalculator.html

[ReesR]

Here is the reply I promised:

<< Tonight, while watching an absolutely wonderful PBS high definition
program I started to wonder if television had reached it's best resolution
which the human eye could discern. >>

That's an interesting question, Rees, and I just don't know the answer. I
don't know if anything transmitted at greater than 1080i would be perceptibly
more distinct to the human brain. And I don't have time to look around for
an answer, since I am leaving in a couple of hours on long flights--Chicago
and then to Raleigh. However, if you do discover an answer, please let me
know. Thanks!

Ted
==============

So, it looks like we still need to do some research. I took a look at the link about pixels and resolution but even there (at the bottom of the page) there are two opinions. One of them knocking the other. Looks like we are getting really close to a good answer though.

I did try the home theater link. That is certainly interesting as well. I discovered that (in my case) by going from a 4:3 46 inch to a 16:9 34 inch I only loose a foot in viewing distance to be optimum. That was really a surprise.

All of this seems at the heart of this forum. Let's continue looking for an answer. I am beginning to think we all are interested in knowing what it is.

MesaV, you quoted the question better than I did and I agree the question is:

What is the resolution of the human eye, and can the figure be quoted in pixels?

I am off to visit Google and other search engines now too. (grin)

[Paul Bethke]

Hey guys, a fascinating question.

But let me add a tangent - are there any TVs out there that even display all 1920x1080 pixels? I have looked a little bit and haven't found any that came close. ?? Perhaps the multi kilo-buck TVs can handle "true" HDTV and display every pixel. I'm anxiously awaiting a set capable of doing so.

Feel free to correct me as I haven't really looked all that thoroughly.

Paul

[ReesR]

ummmmm.......yes

per the atsc standard every hdtv TVs can.

see:
http://www.atsc.org/standards/a_54.pdf

look for Table 5.1 which defines the standard.


1080 refers to the number of active lines while 1920 refers to the number of active pixels per active line. This defines the aspect ratio. 1920/1080 = 16/9 which is the hdtv standard. Hence each HD ready or HDTV complies with that standard.

Hope that helps.

Meanwhile, back at the ranch...

What is the resolution of the human eye, and can the figure be quoted in pixels?



[This message has been edited by ReesR (edited 10-02-2002).]

[ReesR]

This does not fully answer the question but it sure is coming close:
http://www.opticalphysics.com/Vision.htm

Look for this just below the first graph:

"The region where high resolution vision can occur simply by pointing the eyes relative to the head covers a wide field of view. In terms of resolution expressed as pixels, assuming the nominal resolution of the fovea region as 1 arc minute, the region of high resolution vision is equivalent to 24 million pixels. The large number of pixels required to present high resolution images to the eye is quite challenging to the designer of display systems."

But does this answer the question? I am not sure yet.

[Tom Weeden]

Originally posted by ReesR:

"The region where high resolution vision can occur simply by pointing the eyes relative to the head covers a wide field of view. In terms of resolution expressed as pixels, assuming the nominal resolution of the fovea region as 1 arc minute, the region of high resolution vision is equivalent to 24 million pixels. The large number of pixels required to present high resolution images to the eye is quite challenging to the designer of display systems."

But does this answer the question? I am not sure yet.


Rees: Given your TV's screen height, and the fact that your eye can resolve 1 arcminute, you could do some trigonometry (arctangent?) to arrive at the distance to the screen so that 1 arcminute equalled 1 TV scan line. If you were farther than that distance from the screen, then more than 1080 lines would be wasted resolution.

...I think.

[Kevin Arnold]

And to complicate this discussion even further I tried looking up some of my medical references to see what high def. light could be shed on the topic. There's not much specific to the relationship between TV resolution and the eye but there is some interesting concepts.
In the center of the retina is the greatest concentration of rods and cones resulting in the greatest ability to discern image. Traditionally it is measured by the ability to discern smaller and smaller letters i.e. the famous Snellen chart. Black and white yields the best visual acuity because of contrast and because of color - or the lack of it. The eye has the best resolution in black and white. Some maybe we should shut off those colors to get the sharpest picture? Color vision gets much more complicated. Not only is the acuity less but it depends on the color, or more specifically the wave length. The eye has the most problems with the red wavelengths because they are longer, and of course there is less contrast. Blue wavelengths theoretically should yield the sharpest picture. Add to that the natural decrease in acuity as you transition from central to peripheral vision and you have a situation where the resolution of non centrally occuring action or picture doesn't matter as much because the eye won't percieve all the information that is there. The "portrait" lens on still cameras is an exaggeration of this. (Sounds like an interesting compression scheme where you only provide full picture detail for the important part of the picture where the eye is drawn and short change the rest)
So distance from screen becomes very important because being too close may let you see the pixels but also filter out peripheral information and too far loses detail in general. But I guess a black and white high def TV would still be the best. http://www.milwaukeehdtv.org/ubb/biggrin.gif

[oflaherty]

Last month Broadcast Engineering magazine ran an article about visual resolution and TV displays.
It says: “Television system design takes as a reference the visual acuity of the eye, which is of the order of one minute of arc. Picture details that subtend an angle of less than one minute of arc are not perceived by the eye.”

The full story is at: http://industryclick.com/magazinearticle.asp?magazineid=158&releaseid=10505&magazinearticleid=155938&siteid=15

Warning—It’s very technical and involves lots of math. I don’t pretend to understand it all.
---
Sean (in the news dept.) at TMJ

[ReesR]

boy.......taking deep breath

I think I understood the last couple of posts. This is really getting interesting.

The reason I included the link I did was to show that the major area of the eye responsible for high resolution apparently has the equivilent of 24 million pixels. So, I concluded in my non-medically educated head that we more than likely would see improvements in picture quality as screen resolution increased.

On the other hand, the high resolution area is larger than the point of focus for the eye. Right? If this is the case, then we might be closing in on the maximum resolution. True? False?

Does any of this make sense?

[MesaV]

I’m sorry but I have to say this. I was watching Bikini Destinations tonight and I think you’re right kjarnold, who needs peripheral vision… Is that peach fuzz I see?
http://www.milwaukeehdtv.org/ubb/biggrin.gif

[ReesR]

I think MesaV is on to something.

[Kevin Arnold]

Yeah, MesaV is on to something. Surges of testosterone also help sharpen the vision. And with persistance of vision added in it becomes clear that this technology is dangerous.

[MesaV]

LOL… http://www.milwaukeehdtv.org/ubb/biggrin.gif I apologize for taking this thought provoking discussion down the scupper.

[Pat]

Here is a link to a thread from 2 years ago on HomeTheaterSpot.com. The author (yeringto) is known on the Spot for being knowledgeable and reliable.

http://www.hometheaterspot.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic&f=10&t=0014 95 (http://www.hometheaterspot.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic&f=10&t=001495)

[This message has been edited by Pat (edited 10-03-2002).]

[FreQi]

I think you kind of touched on this point, but I wanted to accent it a bit.

One thing to keep in mind about "image quality" is to take note of not only the resolution, but the physical size of the disply device as well. For example, compare a computer screen at a resolution of 1024x768. On a 15" monitor it's pretty nice, but on a 21" monitor, you'll be less impressed. I watch regular SD tv on a 8 foot projector, and I see pixels from as far away as 4 feet, if I look for them. Of course at eight feet, a pixel is about 1/16th of an inch or so (I never actually measured it)...

"In the future" I expect that as tv screens get larger, and wider, these fantstic HD resolutions will have their pixels streatched out to the point where they will be just as fuzzy as today's 27" tv's. But I'll be old and blind by that time, so I guess that's just tough for my niece and nephew ;]

[Greg Oman]

Well, for what it's worth, I recall reading somewhere that the digital vs film threshold is about 8 megapixels. Meaning, at that resolution, you will not be able to tell the difference between the film cameras we all know and digital cameras.

Now if the best film can capture the best image we can process as humans, sweet. I think we just need it to be almost 180 degrees vert & horiz.

Greg O.

[MesaV]

I think that's called the Holodeck.

[ReesR]

but isn't this a still picture comparison?

The number of pixels in a tv screen is 1080 X 1920 or 2,073,600 pixels.

(1920 pixels per line X 1080 lines)

Can we somehow make a comparison with the 8 megabit still to the tv screen? When you said that figure of 8 megabits I too had heard that number somewhere before. I just don't know how they arrived at the conclusion that 8 Megabits was the magic number for still pictures just like we can't seem to come up with the magic number for a high defition screen.



[This message has been edited by ReesR (edited 10-05-2002).]