Human Eyes Resolution?

Discussion in 'Displays' started by Mike~Sileck, Sep 2, 2004.

  1. Mike~Sileck

    Mike~Sileck Supporting Actor

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    I hope this is the right place, at least it's the most relevant here I believe.

    Just out of curiosity, what do we view the world at, resolution wise? Has there ever been any studies done about this?
     
  2. Scott L

    Scott L Producer

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    One eye = roughly 800x600

    Two eyes = 1280x720

    I would not recommend closing one eye if you have two good ones, this is what's known as the human Pan & Scan effect. You're losing over 30% of the picture!
     
  3. Mike~Sileck

    Mike~Sileck Supporting Actor

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    So how much higher than 1080p can we go to the point where we can actually benefit from increased PQ?

    Mike
     
  4. Jimi C

    Jimi C Screenwriter

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    Mike.. when your looking at your tv does it look like you are looking through a window?
     
  5. David K.

    David K. Second Unit

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    cant say since our eyes are not pixel based, so you can not measure with resolution
     
  6. Scott L

    Scott L Producer

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    Yea that's something you can't measure. You're taking a measurement used to make fake images. Our eyesite isn't based on breaking objects down pixel by pixel.

    I'll be happy when displays are 3D and are either object based or throw out a helluva lot of pixels. Oh ya, and interlacing is a thing of the past!

    I was joking in that other post btw. [​IMG]
     
  7. ChrisRuh

    ChrisRuh Stunt Coordinator

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    A normal unaided eye can project an image onto the retina and keep it focused at a distance of no closer than 10 cm. At a 10-cm distance the eye can seperate objects that are 0.1mm apart. If two objects are closer than this distance then the eye will not be able to discern the b/w the two objects (aka "resovling power" or "resolution").
     
  8. PeterK

    PeterK Supporting Actor

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    but don't we have a certain number of rods in the back of our eyes. could we not consider them pixels?
     
  9. David K.

    David K. Second Unit

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    that is not resolution. You can make a comparision but not call it resolution, Once again our eyes are not pixel based, which resolution is

    [n] (computer science) the number of pixels per square inch on a computer-generated display; the greater the resolution, the better the picture
     
  10. PeterK

    PeterK Supporting Actor

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    oops double post

    david answered so fast I thought I forgot to post when I didn't see my name under last post
     
  11. MWestyn

    MWestyn Stunt Coordinator

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    Ultra High Definition Video or UHDV is a digital video format, currently proposed by NHK of Japan

    Resolution: 7,680 by 4,320 pixels.
    Frame rate: 60 frame/s.
    22.2-channel audio
    9 - above ear level
    10 - ear level
    3 - below ear level
    2 - low frequency effects

    Because this format is highly experimental, NHK researchers have to scratch build their own prototype. For example, they used an array of 16 HDTV recorders to capture the 18-minute-long test footage. The camera itself was built with 4 2.5 inch (64 mm)CCDs. According to people who had seen a demo, UHDV is so life-like it could cause motion sickness if the camera moves too much.

    The UHDV format offers 4,000 horizontal scanning lines, HDTV offers 1,000 and standard broadcasts using the NTSC format offer 480 lines out of a possible 525.

    Seeing as most people can't distinguish between reality and UHDV, I'd say our "resolution" is pretty close these specs.
     
  12. ChrisRuh

    ChrisRuh Stunt Coordinator

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    Ah, but you are comparing Biology to Computer Science.

    I offer you this:

    Resolution: the process or capability of making distinguishable the individual parts of an object, closely adjacent optical images, or sources of light

    (source Dictionary.com)

    If you are talking about the resolution of the
    eye.

    Hard to compare the two. It's an apples to oranges comparison.
     
  13. Robert Cowan

    Robert Cowan Supporting Actor

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    i beg to differ... the eye is resolution based, its rods and cones like someone else mentioned... there is also a frame-rate of the eye too. i could look it up and see how many rods and cones there are in the eye.
     
  14. MuneebM

    MuneebM Supporting Actor

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    I disagree. The field of vision of the eye is not limited to a measurable (rectangular) region such as that of a TV screen or computer monitor, and thus cannot be measured in terms of pixels, e.g. 1280 x 1024. If you can show me proof that something like this has been measured I may go back to school and study biology all over again!

    http://66.46.69.23/sigserv/pl/index.pl?p=14
    My DVD Collection
     
  15. John F. Palacio

    John F. Palacio Supporting Actor

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    Before the word pixel even existed there was resolution.
    Resolution can be expressed in lines (as in good-old, analog, NTSC)
    400 or so in the horizontal and 480 vertical.

    Remember VHS = 240 lines? Meaning it can resolve 240 vertical lines across the screen.

    Resolution means resolving power or the smallest possible transition that can be resolved in a given medium or device.

    In the film world it is expressed in lines/millimeter. Or how many lines can be resolved per millimeter of a given film emulsion.

    Optometrists and Ophtamologist measure the resolving power of your eye all the time with their letter chart.

    Digital television gave us the pixel and a new yardstick was added.

    I am not sure what the practical resolution of the average human eye is, but it could be measured. suffice it to say it is much greater that HDTV.
     
  16. ChrisRuh

    ChrisRuh Stunt Coordinator

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    Robert & John, that was my point (see above post).

    Resolution means resolving power or the smallest possible transition that can be resolved in a given medium or device.

    Our eyes can discriminate down to about 0.1mm

    I was addressing the issue of resolution as far as what the definition was for the human eye.

    I agree with what MunbeeM said. The eye is functionally more complex than a camera and sensitivity depends upon the photon fluence rate (light intensity).
     
  17. andrew markworthy

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    Back to school you go. [​IMG] Visual acuity (i.e. the smallest unit that can be distinguished) is very much dependent on the concentration of receptors in your eye - generally the more the receptors, the greater the acuity, as can be seen in cross-species comparisons.

    However, there are several caveats. Let's start at the beginning with Perception 101:

    (1) Light is focused by stretching or contracting the lens (not moving it backwards and forwards like a camera or, for trivia buffs, the octopus's eye). The image is projected onto receptors lining the interior surface of the eye, called the retina (trivia - the receptors actually lie just beneath the retina's surface). The receptors are called rods and cones. Rods respond best in dim light and cones to bright light.

    (2) The centre of the image is projected onto an area of the retina called the yellow spot, or to give it its fancy name, the fovea centralis, which is just under half a millimetre in diameter and contains a very high concentration of cones. As you move out from the fovea, the proportion of cones drops and the proportion of rods increases.

    (3) Okay, what has this got to do with the thread? Well, the truth is that if you simply look at an image without moving the eye, we see very little. The bit of the image which is hitting the fovea can be seen in detail, but as you move away from the fovea, the image gets indistinct. This is largely because the rods in the periphery aren't as good at picking up detail and what's more, are pretty useless at detecting colour.

    (4) The way we see an image is to constantly dart our eyes around it. We are usually utterly unaware of these eye movements (often called saccades) but monitoring equipment can easily demonstrate that in looking at a picture our eyes are all over the place.

    (5) It follows from this that talking about the visual field of the human eye can be highly misleading, because the only way in which we can see normally is to move the eyes around, and hence the visual field is in one sense only limited by how far to either side we want to look.

    (6) However, if we are talking about what can be seen in a single eye fixation, the answer is that we are generally only capable of perceiving a few degrees of arc and the rest is indistinct. As we get towards the periphery of our vision, the most that can be seen is typically gross movement (and if we detect movement our eyes will automatically move to focus on it).

    (7) Okay, so why have cones at all if they are so poor at doing their job? Simple reason - they are excellent for night vision when we need at least a rudimentary sense of vision and movement detection.

    (8) However, that's not the end of it. Acuity varies enormously depending upon several factors, including:

    (a) the physical health of the individual
    (b) whether a person has sight problems
    (c) the age of the person
    (d) the nature of the display - acuity varies according to the degree of contrast. E.g. we can detect much smaller patterns of black on white than e.g. black on grey. The finest acuity a person can detect under different contrasts is known as the contrast sensitivity function, and this changes enormously over a normal lifespan.

    (9) On top of all this you have issues of colour blindness (the cones come in three types optimally tuned to different wavelengths and a defect in one or more type will mean that certain colours cannot be seen), which can also affect acuity (since some contrasts in colours cannot be seen by colourblind people).

    (10) And all this is before the retina sends its signal via the optic nerve to the brain. You also have issues of lateral inhibition, opponent processes in colour coding, the different areas of the visual cortex processing different aspects of the display, etc, etc. All of these refine the image and in doing so distort it. For example, the real world has far lower contrasts between light and dark than you might intuitively suppose. However, our eyes and brains exaggerate the differences. Again, our visual cortex automatically adjusts our colour perception. Camera users will know that unless corrected for, pictures taken outside have a blue tinge, whilst pictures inside have a yellow tinge. This is because the camera doesn't lie and records what's there. But when was the last time you went out of doors and noticed the ambient light switched from yellow to blue? The answer is never - because your brain automatically adjusts.

    In other words, our perception cannot be measured in the same way that e.g. a TV screen's resolution can because perception is far more dynamic, continuous, and inevitably distorts what is there.

    One final thought - it inevitably takes a small fraction of a second to process visual information. What you intuitively think is here and now is in fact what the world was like a fraction of a moment in the past.
     
  18. Chris PC

    Chris PC Producer

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    Its discussions like this that make me feel like I'm going to slip into another dimension...zzzaapp

    One thing I must agree about is the weird cognitive bit involving the fovea. I find it interesting that our minds can create a knowledge of the spaces we inhabit, but if you study how much of your environment you can see in great detail at one time only using the fovea, and not moving your eyes around, you will realize that your world is in your head. I used to think that the world was in front of me and I saw it all with my eyes, but you only see a small amount at any one time. What your brain does, is it takes the information in your peripheral vision and combines it with your memory, what your brain saw with the fovea, if it has seen those objects. You know if you take a look around a room, where the chairs and tables and other objects are, and then you try to navigate around, its no problem, because your brain takes your peripheral vision and extrapolates what it thinks should be there from your memory, the information stored when you looked at the parts of the room with your fovea. You don't believe me? When walking around somewhere you've been before, you feel comfortable and don't have to look around. Now, even if you haven't seen every square inch of the new area, your brain is ok because it has seen trash bins and boxes before, so if you see those in your peripheral vision, your brain says, "no problem, even though I can't see the object in great detail, I'm 99% sure thats a trash bin, and anyways, I can see its rough dimensions and size and I won't let you trip on it". Depending on what you're thinking about and how pre-occupied your are, your eyes will dart around and look at things in your peripheral vision. Sometimes you can't take it all in. This is precisely what I mean by living in a world thats in your head. You don't have to see EVERYTHING around you in great detail, but since you have peripheral vision, you see stuff that is incompletely described in your mind. If our fovea's were too big, I think there would be some other physiological limiation that would arrise. We'd be these big-eyed fish people trying to process way too much detail as we move about. Anyways, thats what I think.

    Alternatively, when driving a car somewhere totally new, you sometimes feel uneasy, not because you're incapable, but because you have to dart your eyes a little more to understand the environment. Same happens with mountain biking. When I ride a trail I've ridden a zillion times, I don't need to move my eyes and head around much. Ride a totally new trail that winds around, you find yourself feeling a little un-easy because you don't know exactly whats beyond your fovea. In fact, looking at my 19" CRT computer screen, I notice cannot see a very large word all together without at least scanning my eyes a little bit. Some may argue you can only see 2 or 3 letters in your fovea at once. I can see words of up to 8 letters or longer without moving my eyes, but the starting and ending letters are still on the peripheral part of my retina, and after that, the letters of larger words are no longer all near the fovea. At least thats what it seems like upon quick examination.

    The one thing I have noticed when it comes to home theatre, is that a big screen is nice, but too big of a screen is un-pleasant. A small TV actually has its benefits. The whole story is right in front of your fovea. With a widescreen movie, you actually have to move your eyes around. Of course, each of the important elements of the screen are more detailed, but there is a limit. I bet peoples preferences vary greatly, but I imagine there is an average size that most people find pleasant, giving a big screen experience, without the need to dart your eyes and head. That is the number reason I hate the first row at a theatre.

    As far as the resolution of the eye is concerned, people needn't get bogged down in semantics. I'm sure that there is a limited number of rods and cones in the fovea and other parts of the eye, and you could measure both what the density is, and the resolution of each of those areas in terms of the light and other visual elements they can detect. You'd have to think studies of this have been done somewhere. I'm going to look.

    Oh, and I'm pretty sure our eyes have a flicker frequency. Below that frequency, we see individual frames or images, above that, we see motion. I think its around 40 to 60. Our peripheral vision is really sensitive to frequency and the like. Set your monitor to 60 hz and look just to the left and right of it and you'll see the flicker more pronounced than when you look straight at it.
     
  19. Robert Cowan

    Robert Cowan Supporting Actor

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    yep, im simply being technical with this one. resolution is loosely defined (for my puroses right now), as the total number of units that make up the picture. whether they be pixels or whatever. the eye (in the way it sees), does not have infinite receptors, but a finite amount, and it actually assembles these receptors to make a solid image, much the same way a digital camera pieces together the information from its CCD to make an image.
     
  20. PeterK

    PeterK Supporting Actor

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    I think the problem is not the comparison of our eyes to a tv but real life to a tv. real life objects have infinate resolution. you can magnify them as much as you want you can even see what the parts that make them look like but those parts are made of other parts and so on. you need to relate your visual acuity to the resolution of a monitor. someone said that we can see objects up to .1mm apart. i am not sure how wide a pixel on a hdtv signal is but i though I heard around .25 mm, maybe i am mistaken. still there is no way to make a tv have real life resolution because real objects have no resolution. even if you had Uhdv tv's you would be able to put a microscope up to one and see the cells of the object on the tv.

    I hope i've made some sense
     

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