When do you do noise reduction?

Discussion in 'Digital SLR' started by Wilba, Nov 1, 2009.

  1. Wilba

    Wilba Guest

    Following from other discusssions of noise and using tools to reduce it, I'm
    interested in when in your process do you do it.

    For instance, I can apply NR in ACR, in Photoshop (e.g. Noise Ninja) before
    resizing, after resizing but before sharpening, or after sharpening. If you
    only did it once, when would you do it? Do you do it more than once, when?

    Thanks, W
     
    Wilba, Nov 1, 2009
    #1
    1. Advertisements

  2. Wilba

    Paul Jaccobs Guest

    It depends on what editing methods you are needing to do. In general,
    noise-reduction is always done first. Any enhancing of a photograph or
    sharpening will also enhance the noise or sharpen the noise as well, making
    it more difficult to remove later.

    However, if you are using a resizing algorithm like bicubic, one that
    always softens details, it might be advantageous to downsize first
    (softening the noise along with all the details), then apply
    noise-reduction. It will be a little easier to remove that way. Continue on
    then with your other editing steps.

    Sharpening should always be done last.

    And yes, sometimes, on rare occasions I will reapply noise reduction twice.
    If some step enhances some subtle noise that I didn't notice before and
    wasn't removed the first time. Depending on how noticeable it is, I might
    even back up all my editing steps or just start over, applying the ND a
    little stronger than I first started with so it won't show up again on the
    enhancing phase of editing.

    Above all, never use a one-size-fits-all automatic noise reduction setting.
    No two images are the same, nor is how the noise will detract from, or in
    some cases enhance the image. It takes experience and an artistic talent to
    know how to use noise-reduction tools well. When it comes to
    noise-reduction software, just like cameras, no one is better than another
    in the hands of someone with talent.
     
    Paul Jaccobs, Nov 2, 2009
    #2
    1. Advertisements

  3. Wilba

    Paul Jaccobs Guest

    It depends on what editing methods you are needing to do. In general,
    noise-reduction is always done first. Any enhancing of a photograph or
    sharpening will also enhance the noise or sharpen the noise as well, making
    it more difficult to remove later.

    However, if you are using a resizing algorithm like bicubic, one that
    always softens details, it might be advantageous to downsize first
    (softening the noise along with all the details), then apply
    noise-reduction. It will be a little easier to remove that way. Continue on
    then with your other editing steps.

    Sharpening should always be done last.

    And yes, sometimes, on rare occasions I will reapply noise reduction twice.
    If some step enhances some subtle noise that I didn't notice before and
    wasn't removed the first time. Depending on how noticeable it is, I might
    even back up all my editing steps or just start over, applying the NR a
    little stronger than I first started with so it won't show up again on the
    enhancing phase of editing.

    Above all, never use a one-size-fits-all automatic noise reduction setting.
    No two images are the same, nor is how the noise will detract from, or in
    some cases enhance the image. It takes experience and an artistic talent to
    know how to use noise-reduction tools well. When it comes to
    noise-reduction software, just like cameras, no one is better than another
    in the hands of someone with talent.
     
    Paul Jaccobs, Nov 2, 2009
    #3
  4. Wilba

    Bob Larter Guest

    I prefer to apply NR in ACR, (or whatever other RAW app I'm using),
    because it seems to me to give the best tradeoff between NR & detail.
     
    Bob Larter, Nov 2, 2009
    #4
  5. Wilba

    Better Info Guest

    Do it before cropping. This way you have more detail-free areas of your
    image to sample the noise from. You do know how to use the noise-sampling
    features of your NR software, I hope. It's the only effective method. The
    homogeneous noise in any larger areas devoid of useful detail, more of
    those being available before cropping, is of the same frequency as might
    appear in all other parts of the image--on a per-image basis. The more of
    those areas you can sample the more effective the NR tool. Cropping first
    can, and usually always will, cripple the NR tool's effectiveness.
     
    Better Info, Nov 2, 2009
    #5
  6. Wilba

    ColinD Guest

    I am a DxO Optics afficionado, and DxO reduces noise during 'developing'
    the raw image, using data specific to the camera sensor and ISO speed
    used, which is coded into the camera model by DxO. Gives approximately
    a four-fold reduction, i.e 1600 ISO will look like 400 ISO. For
    non-camera images like scans I use Neat Image first, before other
    operations.

    Colin D.
     
    ColinD, Nov 3, 2009
    #6
  7. Wilba

    Wilba Guest

    Thanks for all the replies. The general consensus is to reduce noise early,
    as I suspected it would be.

    I just played around with a typical image with those tools and found that I
    got the best results, considering both noise and detail, by setting NR to
    zero in ACR and using Noise Ninja. The advantage appears to remain after
    downsizing (typically 4272x2848 -> 1000x670), but is barely perceptible
    before sharpening and maybe a touch more after. And yes, sometimes no NR is
    better for how I want an image to look.

    I've no doubt I could do better with a lot more work, but just doing that
    puts me ahead of where I was. Thanks again.
     
    Wilba, Nov 3, 2009
    #7
  8. Wilba

    OldBoy Guest

    Yep, DxO :)

    Downsizing reduces noise also, see:
    "Contrary to conventional wisdom, higher resolution actually compensates for
    noise":
    http://www.dxomark.com/index.php/eng/Insights/More-pixels-offsets-noise!
     
    OldBoy, Nov 3, 2009
    #8
  9. Wilba

    stephe_k Guest


    I do it to a layer over the base, then you can erase the NR layer in
    areas that don't need it. Also you can adjust how strong it is easily
    and see the effect (toggle on and off). I do this with digital capture
    and with film scans. I usually get the levels right, then do the NP
    layer thing next is my order. Once I'm happy, flatten and continue
    editing. Once is enough.

    Stephanie
     
    stephe_k, Nov 5, 2009
    #9
  10. Wilba

    Wilba Guest

    This makes sense to me. Stephanie, what tools and methods do you use to "get
    the levels right"?
     
    Wilba, Nov 5, 2009
    #10
  11. Wilba

    stephe_k Guest


    I like the levels tool. First I try the lazy approach and hit options
    and see what the various choices there look like. Make sure preview is
    chosen. The other is to play with the "gray point" and click around on
    the image to see if it does something I like. Then move the sliders to
    taste. If the adjustment look maybe too strong, you can always edit/fade
    this to taste. If you are shooting RAW, it's better to do this in the
    development but for jpegs, the level tool is fairly easy to use.

    Stephanie
     
    stephe_k, Nov 7, 2009
    #11
  12. Wilba

    Wilba Guest

    Thanks. Coming from monochrome wet darkroom experience, the black and white
    points are very important to me.
     
    Wilba, Nov 8, 2009
    #12
    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.