Noise in dark areas

Discussion in 'Digital Cameras' started by Guest, Oct 23, 2003.

  1. Guest

    Guest Guest

    My cam is a Fuji S602. It is in generally considered to have good noise
    performance for a camera with its sensor size, and through most of my use, I
    have no noise issues at all.

    I recently did some experimenting with a one light shots, so one side of the
    subject is well lit, but with signficant shadow area on the blind side (is
    there a "proper" photo term for blind side here?). My aim was to get the
    subject disappearing into darkness.

    Due to poor lighting control (brolly flash, white walls/ceiling), I couldn't
    achieve the effect I wanted, but I did get significant shaded areas on the
    subject. When I had prints done, there was noticable noise in the darker
    regions of the picture, whilst the well lit areas were noise free. There was
    still plenty of detail rendered in the shadows, but the noise draws the eye
    (at least it drew mine when I was examining the shots - maybe most people
    wouldn't notice). The shots were taken at minimum ISO (160), and
    shutterspeed set at 1/500 to remove ambient light (within the quoted synch
    range for the S602).

    My question is, does this happen with all digital cameras? I presume that it
    is related to the Signal/Noise ratio being worse for the darker areas of the
    picture, which would dictate that it would affect all digital cameras in the
    same way, to a greater or lesser degree dependant on sensor
    quality/size/noise reduction algorithmns.

    Please enlighten me :)
    Guest, Oct 23, 2003
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  2. Guest

    Lionel Guest

    Word has it that on Thu, 23 Oct 2003 08:36:59 +0000 (UTC), in this
    To a greater or lesser degree, yes.
    You can get a large improvement by exposing such that the histogram is
    pushed to the right (ie; almost overexposed), rather than centred (which
    is what both you & the camera will attempt to do normally). You then
    drop the luminance of the entire image in Photoshop to get the look you
    want. You should end up with smoother / more accurate tones in the
    shadow areas.

    Do some bracketed test shots & give it a try. ;)
    Lionel, Oct 23, 2003
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  3. Guest

    Canopus Guest

    This is the conclusion I have been slowly coming to with the S602Z. I took
    a lot of pictures in Turkey recently with sharp contrasting shadows and some
    in poor light, also at the moment the only time I can get out to shoot is
    around dusk and in all cases the pictures have come out a little darker than
    expected or had noise in the dark sections. I've been attempting to keep
    the exposure gauge centered, but, am coming to the conclusion to err towards
    over exposure.

    Canopus, Oct 23, 2003
  4. Guest

    Lionel Guest

    Word has it that on Thu, 23 Oct 2003 11:35:39 +0100, in this august
    The drawback with my method is that you have to be anal-retentive about
    checking your histogram for overexposure, but I believe it's a small
    price to pay for the enhanced shadow tones.

    BTW, it's worth mentioning that shadow detail is even worse if you
    expose to the left of the histogram, ie; if you underexpose a little.
    I've found out the hard way (with my 10D) that it's better to overexpose
    (RAW) at ISO 1600 than to almost-underexpose at ISO 400, as brightening
    a dark ISO 400 image will bring the noise-floor of the sensor up into
    visibility, & looks truly ugly, but darkening an ISO 1600 image gives
    quite a nice result.
    Lionel, Oct 23, 2003
  5. Guest

    JPS Guest

    In message <>,
    The only difference between shooting at ISO 400 with a -1 EV, and ISO
    1600 with a +1 EV is the way the analog2digital converter quantizes and
    enumerates the data. The exposure on the sensor is exactly the same,
    and the signal-to-sensor-noise ratio is exactly the same. The noise is
    more visible in the former because of the way it and the signal is
    quantized (2 bits less, for any given dynamic range).
    JPS, Oct 23, 2003
  6. Guest

    Lionel Guest

    Word has it that on Thu, 23 Oct 2003 22:28:11 GMT, in this august forum,
    Actually, the sensor amplifier circuitry & biasing is different in each
    ISO mode. The boosted signal in the high ISO modes is the cause of the
    additional noise in those modes.
    Yes, which is what I was getting at.
    Lionel, Oct 24, 2003
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