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Backlight compensation vs Gain up..

Discussion in 'Camcorders, Action Cams & Video Editing Forum' started by roman700, Sep 8, 2005.

  1. roman700

    roman700
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    Hiya

    I understand that "backlight compensation" is useful if you are taking footage of a subject in front of a very bright background. In this case, your subject may be too dull. Using backlight compensation brightens it up (but it also brightens up the background too)

    As far as I understand, manual gain up increases the signal and hence brightens the whole scene too. Doesn't this therefore give you the same effect as backlight compensation?, ie everything is brightened up, including your subject.

    It seems that gain up increases noise. Is this the only difference between the two features? Are there any disadvantages to backlight compensation?

    Thanks.
     
  2. Roy Mallard

    Roy Mallard
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    Actually they are the same thing more or less, on consumer cameras at least.
    The only ways to brighten the picture on camera is to a) increase shutter duration (motion artefacts) b) open the iris, or c) add gain, or d) all 3.

    Professional cameras have a 'knee circuit' which lets you brighten the picture whilst the camera elctronically clips parts of the picture signal that are approaching peak white.

    This lets you shoot against the sun without sillouette or burn out.

    However you should avoid this practise entirely as you will get flare and fringing, especially on consumer cams.

    Turn your subject 90 degrees to the sun or use lights / a reflector to blunce light back into the subject, creating a better ballance between the backgropund and subject & letting you 'stop down' so that there is no burn out.
     
  3. Paul_Maycock

    Paul_Maycock
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    If possible have your subject in the shade and not having the sun shine directly into their eyes. Use a gold or silver reflector (kitchen foil scrunched up over large piece of thick card) held low and the use of bounce light is also better than direct light.
     

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