Art Adams explains LOG and REC 709 Color Space in relation to finding the best exposures to get the most out of the camera you’re using.
As you can see, each step–which equals one stop–is equidistant from the others. This is not the way cameras see the world, and it’s especially not the way images are meant to be viewed on monitor, but Log is a storage format only, and these equidistant steps give a colorist the most information possible from which to build a look. As you can see information is available right up to the edge of clipping and down to the top of the noise floor. (The way the curve rolls off at the bottom is a side effect of how sensors react at low light levels.)
In the top image you can see that every step is preserved right up to the first chip, which is blown out. (This chart is meant to be used by clipping the first chip and counting down from there, as the only consistent reference point we have with any sensor is where it saturates, or clips.)
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