Re: The Sigma-Foveon pixel rationale

Discussion in 'Digital Photography' started by David J. Littleboy, Apr 1, 2004.

  1. "Dave Haynie" <> wrote:
    >
    > >You refuse to consider this case,

    >
    > Because it's purely artificial. Why should the RGB sensor get twice
    > the light in any fair comparison.


    What you are missing is that there's an _optimal_ (or "natural") ISO setting
    for a given sensor for noise performance. You can't use arbitrarily low
    ISOs, since there's a maximum charge you can hold in the sensor's storage
    elements. The lowest ISO that still gives you adequate latitude at the high
    end is the _optimal_ (or "natural") ISO.

    At the optimal ISO, the RGB sensor will have the same noise as the CMY
    sensor, simply because they are the same underlying sensor.

    So the idea that CMY _reduces noise_ is problematic because the best noise
    performance you can possibly get from a CMY sensor is _identical_ to the
    best noise performance you can possibly get from an RGB sensor.

    So it makes more sense to say that CMY sensors improve sensitivity.

    David J. Littleboy
    Tokyo, Japan
     
    David J. Littleboy, Apr 1, 2004
    #1
    1. Advertising

  2. David J. Littleboy

    John Navas Guest

    [POSTED TO rec.photo.digital - REPLY ON USENET PLEASE]

    In <c4ftv8$20b$> on Thu, 1 Apr 2004 11:03:33 +0900, "David J.
    Littleboy" <> wrote:

    >"Dave Haynie" <> wrote:
    >>
    >> >You refuse to consider this case,

    >>
    >> Because it's purely artificial. Why should the RGB sensor get twice
    >> the light in any fair comparison.

    >
    >What you are missing is that there's an _optimal_ (or "natural") ISO setting
    >for a given sensor for noise performance. You can't use arbitrarily low
    >ISOs, since there's a maximum charge you can hold in the sensor's storage
    >elements. The lowest ISO that still gives you adequate latitude at the high
    >end is the _optimal_ (or "natural") ISO.


    optimal ISO

    1. Usenet. That differential ISO which makes a lower-snesitivity RGB
    sensor no more noisy than a higher-sensitivity CMY sensor.
    Syn: Finangler's Constant

    >At the optimal ISO, the RGB sensor will have the same noise as the CMY
    >sensor, simply because they are the same underlying sensor.


    Circular logic.

    >So the idea that CMY _reduces noise_ is problematic because the best noise
    >performance you can possibly get from a CMY sensor is _identical_ to the
    >best noise performance you can possibly get from an RGB sensor.


    What matters is that CMY has lower noise at any given ISO than RGB.

    >So it makes more sense to say that CMY sensors improve sensitivity.


    Just the other side of the same coin.

    --
    Best regards,
    John Navas
    [PLEASE NOTE: Ads belong *only* in rec.photo.marketplace.digital, as per
    <http://bobatkins.photo.net/info/charter.htm> <http://rpdfaq.50megs.com/>]
     
    John Navas, Apr 1, 2004
    #2
    1. Advertising

  3. "David J. Littleboy" <> writes:

    >What you are missing is that there's an _optimal_ (or "natural") ISO setting
    >for a given sensor for noise performance. You can't use arbitrarily low
    >ISOs, since there's a maximum charge you can hold in the sensor's storage
    >elements. The lowest ISO that still gives you adequate latitude at the high
    >end is the _optimal_ (or "natural") ISO.


    Agree completely.

    >At the optimal ISO, the RGB sensor will have the same noise as the CMY
    >sensor, simply because they are the same underlying sensor.


    Note that you're talking about noise levels at the output of the CCD, or
    at the A/D converter output. But the CMY sensor requires additional
    calculations to turn CMY into RGB, and those calculations subtract
    signal levels while adding noise levels. So the S/N of the RGB output
    from a CMY camera is worse than the S/N of an RGB camera, when both are
    optimally exposed.

    >So the idea that CMY _reduces noise_ is problematic because the best noise
    >performance you can possibly get from a CMY sensor is _identical_ to the
    >best noise performance you can possibly get from an RGB sensor.


    Identical before CMY->RGB conversion. It's worse after conversion.

    >So it makes more sense to say that CMY sensors improve sensitivity.


    At the expense of somewhat worse S/N performance, both at optimum
    exposure.

    Dave
     
    Dave Martindale, Apr 1, 2004
    #3
    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. Dave Martindale

    Re: The Sigma-Foveon pixel rationale

    Dave Martindale, Apr 1, 2004, in forum: Digital Photography
    Replies:
    2
    Views:
    397
    Dave Martindale
    Apr 1, 2004
  2. Dave Martindale

    Re: The Sigma-Foveon pixel rationale

    Dave Martindale, Apr 1, 2004, in forum: Digital Photography
    Replies:
    2
    Views:
    329
    Dave Martindale
    Apr 2, 2004
  3. Dave Martindale

    Re: The Sigma-Foveon pixel rationale

    Dave Martindale, Apr 1, 2004, in forum: Digital Photography
    Replies:
    42
    Views:
    989
    Dave Haynie
    Apr 6, 2004
  4. DM

    Re: The Sigma-Foveon pixel rationale

    DM, Apr 2, 2004, in forum: Digital Photography
    Replies:
    30
    Views:
    871
    David Kilpatrick
    Apr 6, 2004
  5. George Preddy

    Re: The Sigma-Foveon pixel rationale

    George Preddy, Apr 4, 2004, in forum: Digital Photography
    Replies:
    3
    Views:
    338
Loading...

Share This Page