I’ve got Z channel and I want to composite aerial perspective from it (fake of course). I’ve loaded Z, inverted, added gamma and curve to adjust color then merged with main image. After inversion Z looks like front is black back is white.
All is fine exept blue-white fog is added to sky also.
Unfortunately renderer I’m using doesn’t provide alpha channel that’s why I have to “extract” mask from Z or Mat-ID channel (and most probably use it with merge node).
In photoshop I’ve been using action to remove white part of image and replaced with black then added “minimum” filter so border of mask is contracted a little to remove fog from sampled edges like trees.
In Krita there is simple filter color-to-alpha and that’s what I’m looking for in Natron.