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How does a television set generate a display?

  1. Mar 27, 2014 #1
    I'm thinking about Cathode Ray Tube (CRTs) television sets. I'm also studying consciousness and attempting to wrap my cognition around Fourier transformations. There are electronics involved. And there is energy and power involved. However, all of it comes together to develop a visual, right?

    However, that a visual exists is dependent on an individual to acknowledge that there is a visual. So, what I want to know is how a CRT television generates what appears to be a whole television.

    So, let's say that the year is 1993. Let's say I turn on the Zenith television, and The Mighty Morphin' Power Rangers is on Fox.

    mmpr12.jpg

    The television is a color television. Let's assume that I am the observer and watching the television show.

    How does the final image come about?

    Now, I think my question poses some problems, at least when it comes to quantum mechanics. If I understand correctly, the final image on the television comes about because I exist. In other words, I as a concious observer exist. And if I were not there, then there would never be a visual to display nor a television for that matter (assuming no existence of consciousness or a "recording device").

    But, I'm going to throw out the idea that there is a conscious observer. That seems like a problematic variable, but I'm going to keep it there. How does the image on the CRT television come about?
     
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  3. Mar 27, 2014 #2

    russ_watters

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  4. Mar 27, 2014 #3

    dlgoff

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    o-scope1.gif
     
  5. Mar 27, 2014 #4

    nsaspook

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    What's special about a CRT color television? Film or a mechanically scanned system (1930s TV) can capture and recreate an 'Illusion' of the original moving image.
    http://www.movingimage.us/sprockets/illusion.swf
     
  6. Mar 27, 2014 #5

    Averagesupernova

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    I would say that the OP is seriously confused. Bits of light will form on a TV screen whether there is an observer or not. If we choose to call it an image or not is irrelevant as to how it does what it does.
     
  7. Mar 27, 2014 #6

    jim hardy

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    Watch in old movies the television screens in the background. Always one part of the screen is dim, sometimes you'll see lines across it. That's the same effect as wagon wheel spokes appearing to turn backwards.

    The "Picture" is drawn by a fast moving "dot" that's traversing the screen in horizontal lines, 545 of them;
    starting at top and working toward bottom.
    This is repeated thirty times a second.
    Your eye can't see the dot because it moves so fast, and the screen has phosphors that 'persist' for a fraction of a second.. so it looks like a complete picture. But the movie camera can catch the more intense brightness of that part of the screen that's just been re-dotted.

    In 1973 era TV's when you switch off the power you see a bright spot in center of screen for a few seconds. That's the "dot" saying "Whew !" as it comes to rest and the picture tube filament cools down. If you do it in a really dark room you'll see the last image that was on the screen, but very dim - that's the screen's phosphors persisting.

    old jim
     
    Last edited: Mar 27, 2014
  8. Mar 27, 2014 #7

    phinds

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    As Averagesupernova pointed out, you do not understand correctly. The image in no way depends on having a conscious observer around.

    EDIT: also, the moon is there whether you are looking at it or not :smile:
     
    Last edited: Mar 27, 2014
  9. Mar 28, 2014 #8

    davenn

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    haha indeed :smile:

    I cant even imagine how one would think that if a TV was on in a room and no one was in the room to view it, that there wouldn't be a pic on the screen

    reminded me of that old saying ...
    "if a tree falls in a forest, and there's no one around to hear it, does it make a sound ?"


    cheers
    Dave
     
  10. Mar 28, 2014 #9

    phinds

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    Well, THAT one at least is somewhat amenable to a reasonable argument that "sound" to us means that which impinges on our ears and causes us to "hear" things. Yes, it's a dumb definition (should be just something like pressure waves in a material) but it does let you get into a semantic argument.
     
  11. Mar 28, 2014 #10

    meBigGuy

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    In terms of consciousness and object recognition, there is no difference between a TV image and a real moving object. Light is detected by sensors in our eyes, and through high level neural processes we somehow perceive an object.

    For some insight on object recognition and visual processing read the book "Breaking Through" which is an account of a man who regained sight late in life after being blind since 4 years old. His ability to discern objects was slowly regained. Initially he could not recognize a mass of colors as a coke bottle on a table until he felt it. He never did regain facial recognition and was not "tricked" by optical illusions.

    Don't overthink the existence stuff. There is an objective reality that causes the effects we perceive that exists independent of our consciousness. (Bertrand Russell, The Problems of Philosophy)

    You sort of cross and confuse 2 (or more) subjects. Primarily, how a television creates a sequence of light that conveys objects in motion, and how visual processing works.
     
  12. Mar 28, 2014 #11

    nsaspook

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    I think there is a difference between a TV image and a real moving object in terms of consciousness because of the amount of mental effort needed to generate a consistent internal image from the eyes input data when viewing low refresh/data rate images like even HDTV (3D especially). It depends of the level of perception of tiny detail you have trained your mind to see in real-time. (having to be very alert for long periods of time in my case) For me the 'Illusion' is very clearly artificial and fatiguing (I can't watch 3D) as I find myself internally filling in all the missing details by constantly moving my eyes tiny amounts causing eye strain very quickly because I can see (mentally) the image refresh and flicker.
     
  13. Mar 28, 2014 #12

    meBigGuy

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    I don't disagree with what you are saying. There are differences (flaws?) in the light sequences from the TV, compared to the light sequences from a "normally-lit" object, that strain the neural processes. You could play with room lighting and achieve similar uncomfortable effects. If you have a TV that can do higher refresh rates you can see the "soap opera" effect, where images appear more real, and therefore fake. People are (for the most part) used to the amount of blur that is produced when watching motion on TV and movies. Many "psycho-visual" side effects, and individual sensitivities vary widely.

    I consider these differences as secondary effects. The major components of the visual processes involved in object perception and recognition are the same for the two objects.
     
  14. Mar 28, 2014 #13

    phinds

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    Sure, but that's subjective and has absolutely nothing to do with consciousness being present/absent in the sense that the OP is talking about.

    For example, if you carry the OP's conclusion over, very reasonably, to a still photograph, he would be contending that as soon as you stop looking at the image it isn't there any more.
     
  15. Mar 28, 2014 #14

    nsaspook

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    I don't think it's really secondary in the long run if you are young. For a older person it mainly mentally fatiguing but our mental abilities to perform other tasks are effected by the need for the brain to specifically target and utilize areas to specialize on TV viewing when young.
    http://cercor.oxfordjournals.org/content/early/2013/11/18/cercor.bht315.abstract
     
  16. Mar 28, 2014 #15

    sophiecentaur

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    To be fair to the OP, the way a conventional TV display works, does depend upon the visual system of the viewer. If it weren't for the persistence of vision, the display, with normal phosphors, would not produce a flicker-free picture. If our vision were actually 'better' we would see a spot zigzagging along and down the screen and we would not see a moving object on it. As with all visual displays - from pencil sketches to stereoscopic colour displays - the engineering of the system is relying on actual flaws in our vision in order to 'fool' the eye that it sees a real scene. In order to produce a two dimensional representation of a screen with the simple technology that was originally available, it was necessary to transmit a sequential set of samples of the picture by scanning so the transmitted signal was a linear array of (analogue) values which could be transmitted sequentially down a single One Dimensional channel.

    If a TV display were to have phosphors that were all alight at the same time (producing a full image at any instant of time), motion would look totally wrong because of the massive 'lag' which would introduce unbelievable 'smearing' of any depiction of motion.

    The bit of Zen about trees in the forest is not relevant to the question as it was intended - I am sure. The OP wanted a serious knits and bolts answer. (Unless I am very much mistaken.)
     
  17. Mar 28, 2014 #16

    nsaspook

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    I agree that's silly (if that's the OP's conclusion about a still photograph) but maybe indirectly it does point to something. What level of detail do we actually see in real-time at scanned reduced resolution like TV and what amount of dynamic image detail is generated from internal memory patterns that fill the blanks. How many times have you read an article about something you've watched several times on TV or the movies and then had to view it once again because you didn't see it that way but now you did because you expected it to happen after knowing about it? Yes, something is there at all times that can generate the image your human mind 'sees' and it doesn't change just because we aren't looking at it.
     
    Last edited: Mar 28, 2014
  18. Mar 28, 2014 #17

    sophiecentaur

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    Not as silly as it may appear at first sight. The actual image that appears on the screen would actually be pretty meaningless to some other non-human observer. So it really does depend upon the consciousness of the human observer more than we have given the OP credit for. The image produced from a 35mm colour slide projector would be far more like the original for a non human observer - although, in all cases, the perceived 'colour' would be all to hell.

    Perhaps we would need to define what we actually mean by the term 'image' in this case.
     
  19. Mar 28, 2014 #18

    nsaspook

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    This is why I used the word 'Illusion' of a moving image in my first post to the question.
     
  20. Mar 28, 2014 #19

    AlephZero

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    Absolutely. When we do experiments and recording the results on high speed video, we often set up a playback loop of the important part of the test as seen by the various cameras. We have a TV in the office mounted on a wall bracket so everybody can see it, and we just leave the loop playing continuously for a few weeks, so anybody can take a break from "work" and watch it whenever they want, without disturbing other people. It's remarkable how many interesting things get spotted that way.

    But I don't think that was quite what the OP had in mind.
     
  21. Mar 28, 2014 #20

    phinds

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    It seems to me this whole thread has gone completely off the rails relative to the original post, the heart of which was

     
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