| DXO
LIGHTING ENGINE: Local Contrast
Under
the DxO Lighting Tab, one of the controls that has a lot of
potential for adjusting images in ways that other programs
don't, is the Local Contrast setting.
The
DxO literature describes Local Contrast as altering contrast
in a spatially-determined way, and that its effect is similar
to dodging and burning.
Local
Contrast is described as in effect applying a varying tone
curve across the image - unlike global contrast.
Once again, it might be easier to grasp the possibilities
here while looking at how it affects an image.
The
photo here is one I took of a mime in Covent Garden, London.
I used the D2x and the Nikkor 85mm f/1.4D optic at f1.4
For
comparison, here are five versions of the same image:
- the first is with the entire DxO Lighting tab deselected.
ie, no adjustments.
- then there are three variations of the local contrast, 0%,
Auto (28%), and 100%.
- the final version is where I used a blunt adjustment to
the curves to lift the shadow areas, but trying to keep the
highlights the same.
In
these images, you'll notice that the white of the dress and
the mime's white painted face is largely unaffected by local
contrast when set to auto (which turned out to be 28% for
this particular image.) Only the darker background area is
affected and the colours punchier and brighter.
In
racking the local contrast between 0% and 100%, you can
see
the white areas are brighter. However, it looks different
than the S-shaped curve of a global contrast adjustment
would've.
Global contrast would've crushed the white areas, and made
the brighter areas look more flat.
In
comparison, the image where I crudely adjusted the curves
in imitation of lifting the shadow areas, don't look nearly
as good as any of these other versions.
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