Digi-question?

Discussion in 'Digital Photography' started by Mark Johnson, Dec 1, 2003.

  1. Mark Johnson

    Mark Johnson Guest

    I have wondered, in a couple of threads, about this noise vs CCD size
    that people mention. Thanks to someone else posting a related URL, I
    read:

    "Kodak sensor in the E-1 uses 6.8 micron sized photo-sites (pixels).
    The Canon 10D, has 7.4 micron pixels, while the Canon 1Ds has 8.8
    micron pixels. These are all dramatically larger than the roughly 3
    micron sized pixels found in most digicams. For those that haven't
    been paying attention — pixel size is one of the most significant
    determinants when it comes to image quality. All other things being
    equal, the larger the individual pixel size the cleaner and less noisy
    the image produced, and low noise is one of the great advantages of
    digital over film.

    So now we see the conundrum. Make the pixels smaller and you have
    higher resolution from the same surface area. But, you make the image
    noisier and introduce other aberrations."


    So would that about sum it up? Look for the micron size given in the
    spec? Larger means less noise, generally? So you want both megapixels
    ('horsepower') but without the crosstalk ('misfire'). And the only
    reasonable solution is a physically large CCD with the pixels pretty
    well spread out from each other. There's really no alternative to
    that?
     
    Mark Johnson, Dec 1, 2003
    #1
    1. Advertising

  2. Actually, you could reduce electrical noise the way astronomers do -- by
    cooling the CCD. I have not heard of this being done in a handheld camera
    because of the energy requirements.
     
    Michael A. Covington, Dec 1, 2003
    #2
    1. Advertising

  3. Mark Johnson

    Mark Herring Guest

    Mark Johnson <> wrote in message news:<>...
    > I have wondered, in a couple of threads, about this noise vs CCD size
    > that people mention. Thanks to someone else posting a related URL, I
    > read:
    >
    > "Kodak sensor in the E-1 uses 6.8 micron sized photo-sites (pixels).
    > The Canon 10D, has 7.4 micron pixels, while the Canon 1Ds has 8.8
    > micron pixels. These are all dramatically larger than the roughly 3
    > micron sized pixels found in most digicams. For those that haven't
    > been paying attention ? pixel size is one of the most significant
    > determinants when it comes to image quality. All other things being
    > equal, the larger the individual pixel size the cleaner and less noisy
    > the image produced, and low noise is one of the great advantages of
    > digital over film.
    >
    > So now we see the conundrum. Make the pixels smaller and you have
    > higher resolution from the same surface area. But, you make the image
    > noisier and introduce other aberrations."
    >
    >
    > So would that about sum it up? Look for the micron size given in the
    > spec? Larger means less noise, generally? So you want both megapixels
    > ('horsepower') but without the crosstalk ('misfire'). And the only
    > reasonable solution is a physically large CCD with the pixels pretty
    > well spread out from each other. There's really no alternative to
    > that?


    There are lots of tradeoffs here....

    The metric of light-gathering power is called the "etendue" or
    "A-omega". Crudely--it is the product of the pixel area and the
    square of the inverse f/#.** So a small pixel needs a faster lens to
    get the same total light. A small pixel, however, has lower noise.

    Large pixels mean large arrays, which means lower yield and therefore
    higher cost. I suspect that the use of CMOS for the larger devices is
    related to yield.

    one nit: You don't want the pixels "spread out from each other".
    This reduces sensitify and increasees aliasing. The best array--all
    else being equal--will have 100% "fill-factor"--meaning the active
    pixel fills the available space.

    **Precisely, etendue is either of the following:
    1. the product of the pixel area and the solid angle of the exit
    pupil as seen by the pixel.
    2. the product of the area of the entrance pupil and the solid angle
    of the sopt in the object which is mapped onto one pixel.
     
    Mark Herring, Dec 1, 2003
    #3
  4. "Michael A. Covington" <> writes:

    > Actually, you could reduce electrical noise the way astronomers do -- by
    > cooling the CCD. I have not heard of this being done in a handheld camera
    > because of the energy requirements.


    A few of the MF CCD backs do. Imacon for example. PAhase and Leaf as
    well perhaps, but don't quote me on that!

    --
    Paul Repacholi 1 Crescent Rd.,
    +61 (08) 9257-1001 Kalamunda.
    West Australia 6076
    comp.os.vms,- The Older, Grumpier Slashdot
    Raw, Cooked or Well-done, it's all half baked.
    EPIC, The Architecture of the future, always has been, always will be.
     
    Paul Repacholi, Dec 1, 2003
    #4
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Danick Veenstra

    x25 over isdn-2 d-channel / KPN Digi access

    Danick Veenstra, Jan 31, 2005, in forum: Cisco
    Replies:
    0
    Views:
    895
    Danick Veenstra
    Jan 31, 2005
  2. borge

    Another use for digi camera

    borge, Jul 26, 2003, in forum: Digital Photography
    Replies:
    5
    Views:
    569
    borge
    Jul 28, 2003
  3. Rich

    digi cam / usb problem (win XP)

    Rich, Aug 7, 2003, in forum: Digital Photography
    Replies:
    6
    Views:
    1,558
  4. Re: mark up on digi cams

    , Aug 12, 2003, in forum: Digital Photography
    Replies:
    3
    Views:
    311
  5. david

    digi camera

    david, Aug 25, 2003, in forum: Digital Photography
    Replies:
    4
    Views:
    551
    Paul Heslop
    Aug 26, 2003
Loading...

Share This Page