DYNAMIC RANGE AND TONE CURVE


Dynamic Range is measured in exposure values. An increment of 1 in exposure value (EV) corresponds to an increase of one F-stop in exposure. Whether you shoot film or digital, the recording medium and the output medium have a limited range, which is the maximum difference in EV (F-stops) that can be rendered without complete loss of detail in the darkest and lightest areas of the image.

Measure the darkest and brightest area of the scene. This is best done with a spotmeter. Count the EV (F-stops) between the two measurements. If the number of EV exceeds the Dynamic Range of your camera's sensor, or the latitude of your film, then you must sacrifice either shadow or highlight detail. Usually, loss of shadow detail is more accpetable than loss of highlight detail.

The Tone Curve affects the tonal range (gradation) between the end points, which in turn are determined by Dynamic Range. The Tone Curve is adjustable in post processing. You may deliberatly  "clip" shadows and highlights by adjusting the Black and White Point, and you may adjust the tonal range between the Black and White Point.

When you prepare an image for printing, you should adjust the image's tone curve so it will fit within the printing paper's latitude, which is usually around 10 EV. Sometimes, highlight or shadow detail must be sacrificed, because the Tone Curve can be only adjusted within limits without causing undesired effects.




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