Page 1 of 3 123 LastLast
Results 1 to 10 of 21
  1. #1
    Havriliak@aol.com's Avatar
    Havriliak@aol.com Guest

    Default Reciprocity failure in CCD cameras



    Is there any evidence about reciprocity failure in the literature
    about CCD cameras. The manufactures of film routinely publish such
    data. What about manufactures of of CCD chips.
    Intuitively it seems to me that such failure would occur in these
    chips becuse the charges in the wells are not surrounded by infinite
    resistance so that leakage will occur. Thanks for help


  2. #2
    atasselli@hotmail.com's Avatar
    atasselli@hotmail.com Guest

    Default Reciprocity failure in CCD cameras

    Some departure from linearity (up to 95%) typically occurs at around
    75-85% of the full well capacity of the CCDs used in the majority of
    the astronomical CCD cameras (less so in ABG CCDs), AFAIK. It is well
    documented in the chip spec's sheet, usually. Binning the chip to 2x2
    usually yields a linearity of better than 99% for up to 99% of the FWC.

    Regards

    Andrea T.


  3. #3
    Roger Hamlett's Avatar
    Roger Hamlett Guest

    Default Reciprocity failure in CCD cameras


    <Havriliak@aol.com> wrote in message
    news:1116418150.686884.307600@g47g2000cwa.googlegr oups.com...
    Reciprocity failure, is a reduction in sensitivity with reducing signal.
    This does not happen in CCD's at all. The probability of detecting a
    photon of a given wavelength, remains constant up to the point where the
    cells overflow. The potential leakage you are describing, does exist, but
    is smaller than other error sources (you can take a CCD, apply light to
    give a known charge level, then leave it 'unread' for a day, and then read
    the signal - the biggest effect will be an increase in the thermal noise,
    not a drop in the signal itself). The actual capacitive cells in a CCD,
    are similar in structure to those used in certain memory devices, where
    the time to 'leak' 50% of the signal, is measured in years, rather than
    hours/days, with the effect over the shorter timeframe being almost
    unmeasurable.
    Film manufacturers have to publish reciprocity figures, because the effect
    is the main error at low light levels for film.

    Best Wishes



  4. #4
    Roger Hamlett's Avatar
    Roger Hamlett Guest

    Default Reciprocity failure in CCD cameras


    <atasselli@hotmail.com> wrote in message
    news:1116421122.183303.149830@f14g2000cwb.googlegr oups.com...
    That is at the top of the well capacity, not the bottom. "Reciprocity
    failure", is a reduction in light sensitivity at low illumination levels,
    which a CCD does not suffer from.

    Best Wishes



  5. #5
    Chris L Peterson's Avatar
    Chris L Peterson Guest

    Default Reciprocity failure in CCD cameras

    On 18 May 2005 05:09:10 -0700, Havriliak@aol.com wrote:


    The leakage rates are very, very low- a fraction of the dark current
    rate. CCDs are effective photon counters, stable to a few electrons per
    year, right up to the point they cease to be linear or saturate (in both
    cases, at or near the full well capacity for non ABG devices).
    Reciprocity failure isn't specified because it isn't present to a
    measurable degree.

    _________________________________________________

    Chris L Peterson
    Cloudbait Observatory
    http://www.cloudbait.com

  6. #6
    Havriliak@aol.com's Avatar
    Havriliak@aol.com Guest

    Default Reciprocity failure in CCD cameras

    Thank you for all your comments. If there is no substantial
    reciprocity failure in astro CCD's then why not color balance a camera
    using Kodaks color standards using both the gray scale and color chips.
    This proceedure is comon in photography. In my case when I was active
    in wild life photography, I used to save one frame for photographing
    the color standard. Then when I did my darkroom work I would print the
    standard and this would determine all of the artifacts from lighting
    and processing variables. I did this for years. Its not new in
    photography but rather standard proceedure.


  7. #7
    Chris L Peterson's Avatar
    Chris L Peterson Guest

    Default Reciprocity failure in CCD cameras

    On 18 May 2005 09:15:09 -0700, Havriliak@aol.com wrote:


    It is also standard practice with digital sensors. Practically,
    balancing with a gray scale illuminated by sunlight is functionally the
    same as balancing with a G2V star in the image. The latter is just more
    convenient in most cases. You don't need a scale however- a single gray
    or white chip is sufficient, since you aren't usually concerned with
    linearity issues.

    With astronomical imaging the situation is considerably complicated by
    the fact that many targets contain narrow band emission sources
    (something uncommon in normal terrestrial imaging). Such sources put
    much higher demands on the design of tricolor passbands and can make
    color accuracy difficult even for a nominally calibrated sensor. This is
    one reason that DSO images captured by color sensors generally show poor
    colors- even where the same sensor will perform beautifully on planetary
    or terrestrial shots.

    _________________________________________________

    Chris L Peterson
    Cloudbait Observatory
    http://www.cloudbait.com

  8. #8
    Pierre Vandevenne's Avatar
    Pierre Vandevenne Guest

    Default Reciprocity failure in CCD cameras

    Havriliak@aol.com wrote in news:1116432909.105100.145940
    @o13g2000cwo.googlegroups.com:


    There are some color chips used in astronomical CCD cameras (for example
    the SBIG ST 2000 XCM) based on Kodak color chips. Yes, they can be color
    balanced (and tweaked afterwards), but they wouldn't really be useable for
    any type of scientific work with other calibrated filters, or for use with
    narrow band filters. That's one of the reasons, they are others.

    see the long spec of the chip used in that camera

    http://www.google.be/search?hl=en&q=KAI-2001M

    --
    Pierre Vandevenne - DataRescue sa/nv - www.datarescue.com
    The IDA Pro Disassembler & Debugger - world leader in hostile code analysis
    PhotoRescue - advanced data recovery for digital photographic media
    latest review: http://www.pcmag.com/article2/0,1759,1590497,00.asp

  9. #9
    William C. Keel's Avatar
    William C. Keel Guest

    Default Reciprocity failure in CCD cameras

    atasselli@hotmail.com <atasselli@hotmail.com> wrote:

    To amplify a bit - the breakdown of linearity in CCD chips is
    a function of counts/pixel, rather than count _rate_ (which is
    basically where it arises on photographic material). It also
    has a more complicated form - there is actual nonlinearity,
    and before that level leakage sets in wherein the charge is preserved,
    but leaks onto adjacent pixels (and usually right on down the
    column).


    Bill Keel

  10. #10
    Roger Hamlett's Avatar
    Roger Hamlett Guest

    Default Reciprocity failure in CCD cameras


    "Chris L Peterson" <clp@alumni.caltech.edu> wrote in message
    news:aarm811ohlpg0l8qo597d9lr1l4inum072@4ax.com...
    Also remember that the atmosphere itself is a 'filter', and there will be
    a very significant change in the blue recorded in particular, at lower
    elevations. Hence 'calibrations' will need tweaking both for sky
    elevation, and the nature of the source.... :-(

    Best Wishes



 

 
Page 1 of 3 123 LastLast

Similar Threads

  1. CG5-GT Failure
    By WWPierre in forum Telescope Mounts Forum
    Replies: 13
    Last Post: 06-09-2010, 05:26 PM
  2. Provia 400X and reciprocity
    By /D in forum Amateur Astronomy Forum
    Replies: 1
    Last Post: 08-10-2007, 03:17 AM
  3. Kodak E200 PROF and reciprocity
    By /D in forum Amateur Astronomy Forum
    Replies: 1
    Last Post: 08-08-2007, 01:43 AM
  4. Provia 400F and reciprocity
    By /D in forum Amateur Astronomy Forum
    Replies: 1
    Last Post: 04-26-2006, 08:55 PM
  5. Another Failure
    By bwhiting in forum Amateur Astronomy Forum
    Replies: 27
    Last Post: 09-07-2003, 08:58 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBulletin® Version 4.2.0
Powered by vBulletin®
All times are GMT. The time now is 07:49 AM.