ISO noise vs. long exposure noise

Discussion in 'Digital Photography' started by Cynicor, Aug 27, 2005.

  1. Cynicor

    Cynicor Guest

    Does anyone know of any data about ISO noise vs. long-exposure noise? In
    other words, at what point does long-exposure noise become worse than
    the noise you'd add by moving to a higher ISO? I've got a D70, and I'm
    trying to take several-minute-long photos of dunes lit only by the moon,
    but I'm not happy with the results I'm getting. (Someone's got to know
    this - Roger Clark??)
    Cynicor, Aug 27, 2005
    1. Advertisements

  2. Cynicor

    GTO Guest

    Tricky problem. You really need to understand the cause and effect in noise
    theory for CCDs to answer this question. There are three choices, and all
    offer slightly different results:

    1) D70 at ISO 100 using a long exposure (turn the long-exposure noise
    removal on and off for comparison)

    2) D70 at ISO 1600 using short exposure (make sure it's really short, not
    more than 1/2 otherwise you are measuring a subtle combination of things)

    3) Several images using D70 at ISO 400 and "medium" exposure time. Add
    these images via post processing together. This is also known as manual
    integration. Can work great.

    To learn about digital noise and its source, use Google. But much has been
    said and I recommend that your try the three scenarios with different
    settings until you find what works best for you. Your own data will speak a
    thousand words!

    For your application, I would try #2 and #3 since an ISO of 1600 will most
    likely not give you exposure times shorter than 1/2 seconds.

    Also remember, there are very good digital noise removal filters available
    for many programs (e.g. Nikon Capture 4.3.1).

    Please let us know your results.

    GTO, Aug 27, 2005
    1. Advertisements

  3. Here is one study:

    Roger N. Clark (change username to rnclark), Aug 27, 2005
  4. Cynicor

    RichA Guest

    Just remember to use the noise reduction (Dark Frame Subtraction)
    of the Nikon. This will remove "hot" pixels and amplifier noise
    that generates "dark current" when longer exposures are used.
    Also, you can chill your camera down to about 35 deg. F. which
    dramatically reduces dark current. However, exposing the camera to
    a much hotter photographic environment would probably fog the lenses.
    But, if you take a picture now, for say 15 seconds, and then take one
    when your camera has been outside on a winter day and has chilled, you
    will see almost all dark current noise disappear. This is why
    astronomers use dry ice and liquid nitrogen to chill CCDs used for
    long exposures.
    ISO noise is a different issue. Not much you can do about it
    except noise reduction "out of camera."

    "Bittorrents are REFUNDS for all the BAD movie products Hollywood
    never gave us refunds for in the past"
    RichA, Aug 27, 2005
  5. Cynicor

    Cynicor Guest

    I knew that if anyone had looked at it, it would be you. Thanks. :D

    Now the next question is why the guy with the new Rebel pointed at my
    lens hood today and asked what it was, and as a follow-up, would he ever
    get anything beyond his kit lens?
    Cynicor, Aug 27, 2005
  6. Cynicor

    Dirty Harry Guest

    Here is a shot from a 20d for 1153 seconds (20 mins er so).
    full moonlight, noise reduction mode off, iso 100, I was very impressed. I
    think the D70 uses a ccd which can heat up with longer exposures. Something
    else you can try is taking a bunch of shorter pictures and stacking them.
    Here is 40x30 second exposures stacked:
    there are slight gaps in the stars however (I was using mirror lockup and
    the 2 second delay was long enough, I would suggest not using it, noise
    reduction mode is out of the question if you want smooth star trails.)
    Dirty Harry, Aug 27, 2005
    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.