| Apèndix D. Tone Mapping and Shadow Recovery Using GIMP’s → | ||
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| Apèndix D. Tone Mapping and Shadow Recovery Using GIMP’s → | ||
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Sumari
Aquest tutorial prové del www.gimp.org/tutorials i ha estat creat per Elle Stone. Es presenta aquí per a traduccions.
A very common editing problem is how to lighten the shadows and midtones of an image while retaining highlight details, a task sometimes referred to as “shadow recovery” and more generally speaking as “tone mapping”. This step-by-step tutorial shows you how to use high bit depth GIMP’s floating point Exposure operation to add one or more stops of positive exposure compensation to an image’s shadows and midtones while retaining highlight details.
Un problema d'edició és com aclarir les ombres i els tons mitjans d'una imatge sense destrossar-ne les zones clares, sol passar amb fotografies d'escenes il·luminades directament per la llum del sol. Els algorismes que s'utilitzen sovint es coneixen com a algorismes de «recuperació d'ombres». Però en realitat són algorismes de mapa-tonal que de vegades funcionen bastant bé i altres vegades no tan bé, depenent de l'algorisme, de la imatge i de les vostres intencions artístiques respecte a la imatge.
This step-by-step tutorial shows you how to use GIMP’s unbounded floating point Exposure operation to recover shadow information—that is, add one or more stops of positive exposure compensation to an image’s shadows and midtones—without blowing out or unduly compressing the image highlights. The procedure is completely “hand-tunable” using masks and layers, and is as close as you can get to non-destructive image editing using high bit depth GIMP.
Figura 1: línies elèctriques al migdia
Before and after tone mapping (aka “shadow recovery”) using high bit depth GIMP’s floating point Exposure operation.
Fitxer RAW interpolat referit a l'escena.
Després del mapa-tonal/recuperació d'ombres utilitzant els nivells il·limitats del GIMP.
High bit depth GIMP is my primary image editor, and I’ve used the procedure described below for the last couple of years as my “go to” way to modify image tonality. The same general procedure can be used to darken as well as lighten portions of an image, again controlling the effect using a layer mask. This isn’t exactly nondestructive editing because at some point you need to make a “New from Visible” layer. But unlike using Curves, using high bit depth GIMP’s floating point Exposure operation doesn’t clip RGB channel values and allows you to fine-tune the results by modifying and re-modifying the layer mask until you are completely happy with the resulting tonality.
