Bracketing / Merging

(dernière mise à jour :  le 10/04/2003 ) *

& Didier Leboutte

Remark : this problem was suggested to me by Alain Hamblenne.

What ?

How to make a good photograph when there are 2 (or more) light sources that make over/sub-exposed zones ? You can't take a good shot even by bracketing.


How ?

Here just my quick guideline..

On the principle
   1) you put the light image over the dark one.
   2) this tool will work with the light image to make light zones to be transparent, and dark zones to be opaque.
   3) the dark image is not taken into account (perhaps in a next version ?)

On the method :
   1) start with the less effect parameters like this : hue = 1.0, and all others to 0. Keep "triangular".
   2) first adjust the "gap" in order to make a first cut up transparency mask
   3) adjust the "bevel" to smooth the transparency mask.
   4) depending on the images, you perhaps will enjoy the keep a very cut up mask (high "gap" with small "bevel"), or rather a very smooth mask (small "gap" with high "bevel"). Tune "gap" and "bevel" together to make the look as best as possible.
   5) tune the "blur" in order to average local variations. With a cut up transparency mask, a tiny "blur" (3x3 for example) will force small local pixels to adjust their transparency according to their neighbours. With a smooth transparency mask, a large blur (100 x 100 for example) will force local not pertinent transparency zones to adjust their transparency with their neighbours..
   6) with a heavy contrasted scene, increasing the "hue" to a value > 1.0 will enable you to restore some over exposed zones that should not bee too transparente. With low contrasted scene decreasing the "hue" to a value < 1.0 will enable you to set transparent some lightening zone that seems not enough transparent.
   7) you can add a little noise on the mask to avoid stairs effect on large zones.
   8) you can add opaque or transparent rectangle to the mask to force some zones that you can't obtain as you want without conflicting with others..