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Thread: Contrast, dynamic range, latitude, explained

  1. #1
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    Default Contrast, dynamic range, latitude, explained

    Hi,

    I keep seeing that negative films have greater exposure latitude or dynamic range (DR) than slide films, but have lesser contrast. Sounds good, but I still can't wrap my head around it. Can someone explain in more layman terms?

    I get that latitude or DR measures how much a medium can record, and contrast is the difference between the darkness and brightest. So aren't they the same thing? If you can measure a greater range, wouldn't you have a greater difference => higher contrast?

    Cheers!
    Matt

  2. #2

    Default Re: Contrast, dynamic range, latitude, explained

    Dynamic range= difference between highest and lowest(brightest/darkest) value that can be recorded on a medium.

    Latitude=The degree of variation allowed above or below a certain setting, derived directly from dynamic range. i.e latitude a film is for a certain exposure, how many stops of headroom it has above and below before you lose details.

    Contrast= the difference between intermediate tonal values within a certain range. Generally, contrast is inversely related to dynamic range. A wider range allows finer graduations and hence lower contrast if desired. Contrast is directly related to the tonal response of the medium and can be visualized as a curve from light to dark. The steeper gradient of the curve, the higher the contrast at that point.

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    Default Re: Contrast, dynamic range, latitude, explained

    Quote Originally Posted by st11x
    I get that latitude or DR measures how much a medium can record, and contrast is the difference between the darkness and brightest. So aren't they the same thing? If you can measure a greater range, wouldn't you have a greater difference => higher contrast?
    Dynamic range is a property of the image recording medium indicating performance. Contrast is a property of the image. When the contrast of an image exceeds the dynamic range of the medium, something is lost (highlights, shadows, or both). If the contrast is less than the dynamic range, everything is fine - you just don't push the recording medium to its limits.

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    Default Re: Contrast, dynamic range, latitude, explained

    Thanks for the replies.

    After reading and re-reading them, I think Zerstorer you might have just hit the nail on the head with your explanation of contrast.

    So am I correct to say that the way slides will have the tendency to bunch colours that are very close in tone into one?

  5. #5

    Default Re: Contrast, dynamic range, latitude, explained

    Quote Originally Posted by st11x
    So am I correct to say that the way slides will have the tendency to bunch colours that are very close in tone into one?
    In a way, yes, but it depends on the slide you use.

    For instance for Velvia 50 has really high midtone and shadow contrast which gives it its punch while Provia 100F has a much more subtle tones.

    It is possible for 2 mediums with the same DR to have different perceived contrast as contrast is basically the difference between similar tones i.e how the range of values within the DR are allocated.

    You can get a good illustration of the idea just by playing with the curves control in photoshop. The DR is fixed as along as you don't touch the levels controls or shift any end of the curve.

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