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Thread: Dynamic Range

  1. #1
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    Default Dynamic Range

    Just read the comparison of fuji S3 ans S2 DSLRs. S3 supposedly to have a better dynamic range show on the bride's dress here. (Scroll to somewhere near the bottom of the page)

    Now I have a question bothering. How do we quantify dynamic range?

    I have not seen any numbers assigned to cameras quantifying dynamic range.
    So how to know which camera has better dynamic range ?
    (eg: D70 vs 300D vs 20D)

    “How fortunate for leaders that men do not think.” - Adolf Hitler

  2. #2
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    Default More on dynamic range

    Now i know why this thread is so quiet.. It seems that quantifying dynamic range is quite a engineering topic itself.

    Dynamic range is defined by the formula below:

    Dynamic range(dB) = 20Log(full charge capacity/dark current + noise)

    Anyone still interested?

    Somehow temperature, sensor size, ADC bit size, number of pixels as well as pixel size do play a part in the dynamic range level.

    Now, dynamic range increases with pixel.. thinking of which.. fuji's Super CCD range also have larger pixel sizes (octogonal) then similiar sized CCDs. (Giving higher dynamic range?)

    Seems that software also plays a big part in improving dynamic range through multiple samplings.. mmm... interesting

    Too much to digest..
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  3. #3
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    Default

    Quote Originally Posted by yanyewkay
    ...

    Dynamic range is defined by the formula below:

    Dynamic range(dB) = 20Log(full charge capacity/dark current + noise)

    ...
    any idea wat is dark current ?

  4. #4
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    Default Dark Current

    Dark Current is the signal read when the CCD is exposed to a 'no light' condition. I guess this is the signal responsible for the noise when doing long exposures at night.
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  5. #5

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    Dynamic Range as I understand it, can be measured in stops. Just like the f-stops on your camera. As you know, once you know the correct exposure at a particular ISO say f16 at 1/200 for 200 ISO, you can get the same exposure by varying the f-stop and shutter speed. Opening the f-stop by 1 stop to f8 and increasing the shutter speed to 1/400 will give the same exposure.

    A stop of light is basically a doubling or halfing of light recorded by the camera. The dynamic range for slide film and most DSLRs is about 5.5 stops. Print film has a dynamic range of 7 stops and our eyes have a dynamic range of about 13 stops. This means that our eyes can see a wider range of tones compared to film or sensors.

    This is most evident when we try to take a building that is relatively dark against a bright blue sky. If we metered the building, we'll find the sky reduced to a featureless white. If you meter off the sky, the building is completely black. In both cases the range of tones of the building and the sky are more than 5.5 stops a part and cannot be captured by film.

    An example and a method for increasing dynamic range is shown here : http://forums.clubsnap.org/showthread.php?t=93942

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