Raphaël Quinet (quinet@xxxxxxxxxx) wrote:
> Your example is fine, except for the last step using Noisify on the
> alpha channel. As Adam pointed out in his previous messages, the
> correct way to acheive the same effect would be to use Noisify on a
> layer mask, not on the alpha channel.
Be careful: A layer mask can *not* do everything you could do with
manipulating the alpha channel directly. Especially it is impossible to
increase the opacity of the layer with a layer mask.
Imagine a blurred circle on a layer and you want to make the transition
to the transparency non-linear, e.g. more like a cosine. Basically this
is impossible with a layer mask, because it cannot increase the opacity
in some areas. Also - if we talk about more complicated shapes - it
might be very tedious to manipulate the layer and the layer mask
synchronously.
Of course this example can be done very conveniently with the curves
tool on the alpha channel, but you have to make sure that accidental
changes to total transparency do not throw away the color information
until the tool is finished.
A layer mask is not a substitute for manipulating the alpha channel
directly!
Bye,
Simon
--
Simon.Budig@xxxxxxxxxxx http://www.home.unix-ag.org/simon/
