PanoTools NG:
Re: OT: Local Contrast
Ian Wood 2006-Nov-13 21:31:24
On 13 Nov 2006, at 19:43, Bob Smith wrote:
> On Nov 13, 2006, at 10:38 AM, Ian Wood wrote:
>
>> Carel is trying to increase *local* contrast, not *global* contrast,
>> so curves aren't appropriate in this case.
>
> local meaning only part of the tonal range... all of the image except
> the lightest 5 percent as in your example. Not local meaning just a
> portion of the frame. That's exactly what proper use of curves can
> achieve and it doesn't produce the type of artifacts that can occur
> with USM.
>
> Bob Smith
Looks like we're using different definitions for the phrase 'local
contrast'.
In digital imaging it's almost universally used to mean increasing
the contrast of pixels depending on the surrounding pixels. In much
the same way that shadow/highlight tools affect contrast locally by
area rather than by tonal range.
Curves adjustments by definition affect global contrast unless there
is masking involved - lightening the 25% area of the graph will
lighten that tone globally throughout the image, regardless of the
surrounding pixels.
Apologies if my first reply came across rudely, it wasn't the intention.
Ian
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