How does screen size effect picture quality

Discussion in 'Apple TV and Home Theater' started by rdsii64, May 28, 2011.

  1. rdsii64 macrumors regular

    Joined:
    May 14, 2008
    #1
    I have a 1080P 73" Mitsubishi DLP. I totally love this TV even if it isn't the newest tech. I Think I under stand resolution and how it effects picture quality. Please correct me if I am wrong. If you have 1080 lines stacked top to bottem that are 1920 pixels wide you can put more information on a screen with more detail that if you has less lines that were shorter in width because you have fewer pixels. Also, if my understanding is correct, two tv's having the same resolution but not the same size screen will still have the same pixel count. The difference being the larger screen will have larger pixels. All else being equal for my
    73" screen to look as good as a comparable 60" screen displaying the same 1080P content viewed from the same distance, the 73" screen would have to have higher resolution to match the pixel size of the smaller screen. Am I close to being correct? If not where am I going wrong.
     
  2. waw74 macrumors 68030

    Joined:
    May 27, 2008
    #2
    basically, you're correct.

    check out this chart

    the further you are from a screen the bigger the pixels can be. a lot of the big screens like you see in times square are probably 15-20 mil panels, meaning the pixels are 15 to 20 millimeters apart, if you get into something that is supposed to be viewed closer, i've seen 5 mil panels.

    there is one big sign in times square (walgreens i think) that goes up the side of a building, about 15 stories, the bottom being about 15-20 feet off the street. it actually has 3 different pixel densities as it goes up, wider spacing is cheaper, so no need to put the higher density up top.
     
  3. ftaok macrumors 601

    ftaok

    Joined:
    Jan 23, 2002
    Location:
    East Coast
    #3
    yes

    yes

    Yes, but no one makes a TV with resolution higher than 1080p. So at the same distance, the 60" TV may look sharper (depends on the distance and your eyes - an extreme example would be a viewing distance of 20 ft)
     
  4. kuwisdelu macrumors 65816

    Joined:
    Jan 13, 2008
    #4
    If two screens are the same resolution, and disregarding the quality of the screen itself, the only way the size effects the picture quality is how far away you can sit from it.
     
  5. Irishman macrumors 68030

    Joined:
    Nov 2, 2006
    #5
    Good start there. Also, if you take two 1080p HDTVs (one 46" and one 73"), and you feed them the same signal (blu-ray, say), the smaller set will look sharper than the larger one.
     
  6. bobr1952 macrumors 68020

    bobr1952

    Joined:
    Jan 21, 2008
    Location:
    Melbourne, FL
    #6
    That's really a neat chart--I seem to have been right in my own situation when I got my 55" 1080p TV and just was not happy with the definition at 12 feet. So I moved into a smaller dedicated theater room with a view distance around 8 ft--much better--and very close to the red line in that chart! :D
     
  7. Avatar74 macrumors 65816

    Avatar74

    Joined:
    Feb 5, 2007
    #7
    It's all about pixel density, and there's a threshold to that. Most experts tend to agree that the human eye is relatively poor on image clarity and contrast... about 300 pixels per inch in full color, and 500:1 contrast ratio.

    At 20 inches, a 720p screen has a 72-73 dpi resolution. This is a typical computer monitor pixel density. Already, your eyes will distinguish a lack of detail between that and the real world. A 1080p display of 20 inches would have 110ppi... and that number only gets smaller and smaller the larger screen size you go (100 inches @ 1080p = 22ppi). A negligible difference, and still visible to the naked eye... but only consciously so if you're constantly comparing the image to something of higher pixel density, and sitting up close to the screen. And there's the rub. You can always adjust how far back from the screen you sit. But even more than that, the brain adjusts to the stimuli pretty well...

    Think about the way your brain fills in the gaps with 24fps motion... our eyes do not process motion information fast enough (unlike dogs, who perceive 24fps as a series of still images, and not continuous motion). Likewise, when you're looking at lower resolution displays for long periods of time... your brain doesn't care. The only time you're REALLY going to notice is when you compare... and this is how manufacturers get you.

    It's a phenomenon known in medical circles as Keeping Up With The Joneses Disease. It's very hard to treat... and there is no known cure, except a steady dosage of common sense.
     
  8. Che Castro macrumors 603

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    May 21, 2009
  9. Avatar74 macrumors 65816

    Avatar74

    Joined:
    Feb 5, 2007
    #9
    36ppi at 0 feet. So if 72ppi is the pixel density on a 30 inch 1080p (which it is), then you have to sit twice as far away from a 60 inch screen to get the same relative visual clarity.

    This is partly why I fail to see the benefit. Why spend thousands more for a much larger display only to end up sitting twice as far away and consequently having the much larger screen occupy the same amount of your field of vision?

    There are only two reasons for this: Either to entertain larger groups of people, or to impress your neighbors. Anything beyond that is purely aesthetic...e.g. do you really need a gigantic living room (costing you yet more money)?

    I haven't done the math but whatever distance you sit at, as long as it effectively causes the pixel density of the display to be perceived as close to 300ppi as possible, that's within the threshold of photorealism to the human eye. Anything above 300ppi isn't perceptibly distinguishable by the human eye.

    The biggest leap in quality is from SD to HD primarily because of the increase in color density (about 4x the range of color detail as SD) and better chroma subsampling (4:2:0 instead of DV NTSC's 4:1:1, though Digibeta masters are 4:2:2). This is far more important than overall image resolution, frame rates or contrast ratios... because while the eye cannot do better than 300dpi, still perceives 24 frames per second as continuous motion (unlike a dog whose motion perception is so acute that 24fps looks like a series of still images to them), and no better than 500:1 contrast, the human eye can detect differences in wavelength of as little as one nanometer.

    So my suggestion, as with many types of technology, is to spend in the bottom tier of the best format/technology, or the top tier of the outgoing technology (to get huge discounts)... rather than top of the top, which is bound to depreciate in value more rapidly.

    I paid $900 for Sony's last CRT HD model... the best, most advanced of an outgoing technology ... an XBR WEGA 34". You'd be hard pressed to find an LCD flat that has better color, clarity and contrast at ANY price, even today, than that TV. I got my money's worth... and Trinitrons are known for lasting 10-20-30 years.
     
  10. ftaok macrumors 601

    ftaok

    Joined:
    Jan 23, 2002
    Location:
    East Coast
    #10
    People typically buy the house before buying a TV, so you buy the size TV that fits the room. Most larger houses have larger living/family rooms, so you'd need a larger TV.

    I don't know of anyone who bought/built a family room with a particular TV in mind.
     

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