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Thread: Permutations

  1. #1 Permutations 
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    Hi, Does anyone know, How many photographs a digital camera can take, in theory??
    Suppose a 10megapixel Camera.
    As far as i know there are 252 different choices of colour/shade per megapixel.
    if that's the case the total permutations would be 252 to the power of 10,000,000.

    Not sure if my understanding of digital cameras is correct, perhaps someone can enlighten me.

    I just think it's interesting that a digital camera can pretty much cature any image a human eye can see.

    I once calculated in my head that the physical size of a harddrive used to store every permutation(not combination) would be about as big as the Solar System.


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  3. #2  
    Veracity Vigilante inow's Avatar
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    EDIT: Totally misread the question and whiffed on the reply. Apologies.


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  4. #3  
    Forum Radioactive Isotope MagiMaster's Avatar
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    252 colors per pixel sounds really low, but on cheaper cameras it might happen. Your monitor shows 2^24 (about 16.7 million) colors per pixel.

    For a 10 megapixel image (roughly a 1200x900 image) with 252 colors per pixel, yeah, it'd be 252^(10,000,000). I think most cameras take 24-bit color images, so that'd be (2^24)^(10,000,000), which works out to 2^(240,000,000) or about 10^(72,000,000). A massive amount of possibilities.

    There was another thread on this recently. In that, I did a bit of math that showed that even for a 256x256 black-and-white image, there's not enough matter in the universe to store the entire set, even using some specialized compression. (Edit: here it is.)
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  5. #4  
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    Thanks MagiMaster,

    i just don't get how a computer monitor displays from a choice of 16 million, Per Pixel.

    Didn't the old Cathode ray tube TV show a nice image with only 3 choices per pixel; red, blue or green.

    I mean if theres 16 million choices per pixel, a simple picture would require 'lots and lots and lots' of gigabytes of electronic info to distinguish it from all other possibilities/permutations(even with the best compression software)



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  6. #5  
    Forum Radioactive Isotope MagiMaster's Avatar
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    One uncompressed 10 megapixel picture would take (10,000,000 pixels * 3 bytes per pixel) or 30,000,000 bytes. 30 MB isn't too bad for just one picture, but compression will typically reduce that significantly.

    A cathode ray tube can show much more than 3 choices per pixel. The key here is that there are shades of color for each of the primary colors. A typical pixel is stored as an RGB triplet. For 24 bit color, each color gets 8 bits, or 256 shades. I'm not exactly sure how many shades a CRT can really handle, but in memory, it's been 24 bit for years now. (Actually, a CRT is analog, so it can theoretically handle any shade, but there are technical limitations.)

    If you want to see what just 16 choices (each color is either on or off, with one more bit for bright or dark) looks like, go look at some old CGA programs/games. I don't know of any hardware that used less than that (at least not off the top of my head).
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