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Thread: Hi ISO Noise Reduction

  1. #1

    Hi ISO Noise Reduction

    Is there an advantage or disadvantage, to setting the "Hi ISO NR" in your camera if you shoot in RAW and post process? I'm wondering if it's worth setting "in-camera" if I'm going to post process in Lightroom and if the results will be any better using both options.

  2. #2

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    Re: Hi ISO Noise Reduction

    No. And while we cannot assume that RAW is going untouched in many cameras these days, it would be logical to assume that NR setting would likely be useless for RAW output and applies only to out of camera JPEGs.

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    Re: Hi ISO Noise Reduction

    Quote Originally Posted by Tommy49 View Post
    Is there an advantage or disadvantage, to setting the "Hi ISO NR" in your camera if you shoot in RAW and post process? I'm wondering if it's worth setting "in-camera" if I'm going to post process in Lightroom and if the results will be any better using both options.
    Makes no difference.

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    Re: Hi ISO Noise Reduction

    What does make a difference in shooting raw is long-exposure noise reduction, if your camera has it. On my camera, I believe this only works with exposures >1 minute. The camera takes a second exposure with the shutter closed. The pattern noise generated with long exposures will be mostly the same, so the camera subtracts the second image from the first, if I understand it right. I use this routinely for long-exposure macro shots, even though I use regular NR as rarely as possible.

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    RustBeltRaw's Avatar
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    Re: Hi ISO Noise Reduction

    Built-in noise reduction methods can be quite good for JPEGs. Who knows a camera's high-ISO problems better than the people who made it? But I don't believe it's applied to RAW files.

    The technique Dan describes is called dark frame subtraction. Essentially, the sensor has a certain amount of noise at all times, regardless of whether light's hitting the sensor. By taking a shot with the body cap on or the shutter closed (the dark frame), at the same settings and for the same duration as the actual shot, you can subtract the dark frame's noise from the final shot. Astrophotographers use this all the time. I've never needed to, since my camera (to my knowledge) has no hot pixels, but I do use long-exposure noise reduction. Longest shot I took with it was a 9-frame HDR in the Basilica Cistern. Between the dark frames and the actual frames, the total time for the photo was over 7 minutes.

    Good step-by-step on dark frame subtraction here.

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    Administrator Manfred M's Avatar
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    Re: Hi ISO Noise Reduction

    Interestingly enough, the dark frame subtraction is built into higher end video cameras (the sensor stays on for longer intervals and thus gets hotter, so is more susceptable to this noise). It is often referred to as "automatic black balance" and on my camera it is built into the white balance switch. The dark frame noise is subtracted from the recorded image automatically.

    I find it a bit strange that still camera manufacturers do not include this functionality, as part of the video functionality.

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    Re: Hi ISO Noise Reduction

    Quote Originally Posted by RustBeltRaw View Post
    (...)I've never needed to, since my camera (to my knowledge) has no hot pixels, but I do use long-exposure noise reduction. Longest shot I took with it was a 9-frame HDR in the Basilica Cistern. Between the dark frames and the actual frames, the total time for the photo was over 7 minutes.
    (...)
    In which case you did use black frame subtraction, but your camera handled all the dirty details... If your manual states that long exposure NR needs twice as much time per image, then your camera does the 2nd exposure and subtraction 'behind the scene'.

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    Re: Hi ISO Noise Reduction

    You think the camera is slowing down but actually it is busy working away for you
    Manfred's video camera wets my appertite

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    RustBeltRaw's Avatar
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    Re: Hi ISO Noise Reduction

    Quote Originally Posted by revi View Post
    In which case you did use black frame subtraction, but your camera handled all the dirty details... If your manual states that long exposure NR needs twice as much time per image, then your camera does the 2nd exposure and subtraction 'behind the scene'.
    I should clarify that I've never had to in Photoshop. Good catch.

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    Re: Hi ISO Noise Reduction

    Quote Originally Posted by RustBeltRaw View Post
    I should clarify that I've never had to in Photoshop. Good catch.
    I thought as much

    One advantage of doing it in photoshop (or whatever raw developer you use) is that you can get away with one black frame per time/ISO combination, and that you can take them at another time (say the next day or so, but preferably at a similar temperature). And that means that you don't have to wait between shots during a shoot (quite nice when doing star trails with multiple long expositions).

    Btw, this is not properly speaking high ISO noise reduction, but long exposure NR. (Strictly speaking it's not even noise, as it is not random: the hot pixels are always in the same place, and always behave the same...)

    High ISO noise is real noise, so totally random, and made more visible by the extra amplification of the sensor signal. It's the same noise you see when increasing the brightness of a low ISO image (but there are very good reasons to prefer the high ISO setting and expose properly for that setting, just try it).

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