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What is noise? - Photography

I'm new to this, as you will see, and don't understand references to "noise" in digital photos. Thanks for explaining. Best, Howie...

  1. #1

    Default What is noise?

    I'm new to this, as you will see, and don't understand references to "noise"
    in digital photos. Thanks for explaining.
    Best,
    Howie


    Howard Guest

  2. #2

    Default Re: What is noise?

    In article <9whRa.4941$prod.itd.earthlink.net>,
    "Howard Wettstein" <net> wrote:

    Your post was noise.

    --
    Enough <com>
    Enough Guest

  3. #3

    Default Re: What is noise?


    "Howard Wettstein" <net> wrote in message
    news:9whRa.4941$prod.itd.earthlink.net... 
    "noise" 
    What is usually referred to as noise in this NG looks much like grain in
    film photos. Technically,.noise is unwanted, random variation in a signal.
    In digital photography, an image is obuilt up from the signals that are read
    from each pixel. But a pixel generates a small signal randomly - each pixel
    does it a little differently. That is noise. In a short exposre, with
    ample light entering the camera, this noise is not very noticable. But in
    low light, where the exposure is longer, the noise in each pixel grows
    larger, and it becomes noticable.

    In og TV, the source of noise is different, and it is commonly called
    "snow". It often comes on the way between the TV transmitter and receiver,
    like static on radio.


    Marvin Guest

  4. #4

    Default Re: What is noise?

    Howie wrote: 

    I'll explain the typical example of what we call color noise. This is typically
    worse when the ISO sensitivity is set to a high number, and it is typically
    best when the ISO is a low number.

    Suppose you shoot a picture in a semi-dark room with no flash. What do you get?
    You get a picture with lots of grey and black. OK, now go in and scan it at
    high resolution, or view it with the magnification set very high. You will see
    the "grain" if this were a film image, but in digital, there isn't any grain.
    Instead of it being continuous tones of grey or black, you will see a little
    scattered pixels of odd color, like pink or other pastels. When you look with
    high magnification, you will see this, but if you simply look at the overall
    shot, you don't see it. Well, if those odd-color pixels get too bad, you will
    call that color noise.

    ---Bob Gross---
    Robertwgross Guest

  5. #5

    Default Re: What is noise?

    > I'm new to this, as you will see, and don't understand references to
    "noise" 

    http://www.dpreview.com/learn/Glossary/Digital_Imaging/Noise_01.htm

    Cheers,

    -Jorge


    Jorge Guest

  6. #6

    Default Re: What is noise?

    Howard Wettstein writes:
     

    Noise refers to visible features of an image that don't represent the
    scene being photographed. It is caused by thermal disturbances in the
    image sensor and other sources, instead of by light coming from the
    scene being photographed. It usually looks like a graininess or sandy
    texture in the photo, especially in areas that are otherwise smooth and
    clean (such as the sky). It's more obvious for photos taken in
    darkness, in warm weather, and with long exposures (such as night
    photos).

    An equivalent phenomenon with film photography is film grain, which
    looks very much the same, even though it has a completely different
    cause.

    --
    Transpose hotmail and mxsmanic in my e-mail address to reach me directly.
    Mxsmanic Guest

  7. #7

    Default Re: What is noise?

    In message <com>,
    Mxsmanic <com> wrote:
     

    I don't know if I would say they look the same. Film grain tends to
    scatter the effective light distribution in each emulsion layer, and is
    mainly a luminance noise, and a displacement. CCD/CMOS noise is random
    positive spikes of color in the blue and red channels, and has very
    little effect on luminance (which is determined mainly by the green
    channel).
    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <komm> 
    JPS@no.komm Guest

  8. #8

    Default Re: What is noise?

    In message <com>,
    Mxsmanic <com> wrote:
     
    >
    >Perhaps not exactly the same, but they are both very irritating, which
    >is all that counts for me. I don't like noise or grain.[/ref]

    The Canon 10D in ISO 100 has neither. Of course, this may lead to
    visible banding of extremely out-of-focus areas on a 24-bit display, so
    a little dithering of added noise might be welcome.
    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <komm> 
    JPS@no.komm Guest

  9. #9

    Default Re: What is noise?

    komm writes:
     

    It appears to have very little; the same is true for the 1Ds (but also
    for a number of other high-end cameras). Now, if only they had
    resolution to match, and competitive prices, they might be a lot more
    attractive.

    --
    Transpose hotmail and mxsmanic in my e-mail address to reach me directly.
    Mxsmanic Guest

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