contrast and saturation in camera or software

Discussion in 'Digital SLR' started by mike regish, Apr 11, 2005.

  1. mike regish

    John Francis Guest

    1) Not unchanged from the original; unchanged from the value that would
    be calculated if the row (or column) of zeros were not present.

    2) If a matrix has a row (or column) of zeros, it doesn't have an inverse.
     
    John Francis, Apr 12, 2005
    #21
    1. Advertisements

  2. mike regish

    Alan Browne Guest


    1) Not unchanged from the original; unchanged from the value that would
    be calculated if the row (or column) of zeros were not present.

    2) If a matrix has a row (or column) of zeros, it doesn't have an inverse.
    [/QUOTE]

    I give up. You're flogging me with all the math I've forgotten (or
    learned badly in the first place).

    Cheers,
    Alan

    --
    -- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
    -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
    -- slr-systems FAQ project: http://tinyurl.com/6m9aw
    -- [SI] gallery & rulz: http://www.pbase.com/shootin
    -- e-meil: Remove FreeLunch.
     
    Alan Browne, Apr 12, 2005
    #22
    1. Advertisements

  3. Alan Browne wrote:
    []
    But you do understand that if any operation is non-linear, it may not be
    possible to undo it?

    David
     
    David J Taylor, Apr 12, 2005
    #23
  4. mike regish

    Alan Browne Guest

    *may*, yes. There are many non-linear operations that can be done as
    long as they are undone in the right order and that all the parameters
    are known. One example of where it is definitely impossible is in USM.
    Even if you know the parameters used, you cannot know which modified
    pixels have been affected due to the theshold setting.

    Cheers,
    Alan.

    --
    -- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
    -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
    -- slr-systems FAQ project: http://tinyurl.com/6m9aw
    -- [SI] gallery & rulz: http://www.pbase.com/shootin
    -- e-meil: Remove FreeLunch.
     
    Alan Browne, Apr 12, 2005
    #24
  5. mike regish

    googlegroups Guest

    If you have the RAW file available then there's no need to keep the
    settings neutral - the JPEG version will be saved by the camera as
    configured (which may be irreversible), but the RAW version will simply
    be tagged with those non default parameters. You can manually override
    those settings on a per image basis in your conversion program.

    So, configure your camera for the most aesthetically pleasing default
    output, then if some images don't look 100% right you can play with the
    settings before converting them from RAW...

    This is speaking from a Canon perspective, other manufacturers may
    differ.
     
    googlegroups, Apr 12, 2005
    #25
  6. mike regish

    Paul H. Guest

    Sharpening works via an algorithm that increases the contrast between a
    given pixel and its adjacent pixels. If you were trying to undo the effects
    of a sharpening operation, how would you tell if a particular contrast
    difference in the sharpened photo was due to the operation of the sharpening
    algorithm or if the difference was present in the original photograph by
    coincidence? You can't: In other words, there are a vast number of
    photographs which could map via the sharpening algorithm into the same
    sharpened photograph and thus it's impossible to make the reverse mapping.
    (BTW, "contrast" was used in a general sense.)

    Sharpening increases the entropy in the photo and only isentropic changes
    are reversible.
     
    Paul H., Apr 13, 2005
    #26
  7. mike regish

    John Francis Guest

    To be pedantic; it's not the sharpening operation, per se, that affects
    the entropy (as I've already shown in a different branch of this thread);
    it's the rounding of the result to an integer value.
     
    John Francis, Apr 13, 2005
    #27
    1. Advertisements

Ask a Question

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

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.