Hi Bruce,
you can consider the strength of the module's effect to be controlled by
two gradients or ramps. One for the highlights and one for the shadows.
The shadows gradient has its maximum value at L=0 and linearly goes down
in the direction of the highlights. For the highlights gradient it's
vice versa.
The compression slider controls the steepness of the two gradients.
With the default setting 50% both gradients reach a value of zero (= no
effect) at L=50 - which means that only an ideal midtone is not affected
by neither shadows nor highlights.
At a compression value of 100% the gradients are practically vertical -
only pure black and pure white are affected - a corner case which has
virtually no effect on the image.
At a compression value of 0% both gradients extend to the respective
opposite side. The shadows adjustment strongly affect shadows,
moderately affects midtones and minimally affects highlights. Vice versa
for the highlights adjustment.
Best wishes
Ulrich
Am 14.11.18 um 13:15 schrieb Bruce Williams:
Hi all,
Andreas suggested I should seek clarification on the compression slider,
specifically in the "shadows and highlights" module.
The manual doesn't explicitly state what ranges of shadow and highlight
values are affected for given compression levels.
In my latest video, I suggested that at 0, the shadows control would
control all dark tones up to the mid point, and the highlights slider
would control all tones from the mid-point up to the brightest/whitest
pixel.
Does a compression setting of 50 mean the shadows slider covers the left
25% of the histogram, and the highlights slider controls the right 25%
of the histogram?
Cheers,
Bruce Williams
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