custom masks

[samsc]

somewhere in here is the problem of pre-multiplied alpha - or not....

an extra complication. im not even sure about this issue myself - but it certainly affects compositing.

http://www.td-grafik.de/ext/xfrog/alpha/
http://www.gimp.org/docs/plug-in/appendix-alpha.html

[samsc]

TIFF with alpha transparency - doesn't show up in the server at all - blank pane.
TIFF white-black w additional alpha - shows up as black.
TIFF white-black, straight - Comes up fine in server as white-black. Color effects applied to it (best: "invert mask 2") work to an extent.

sound to me like you didnt successfully save transparency in your tiff file.

there is a second tiff options dialog in photoshop cs when you save a tif.
it has an option 'save transparency'.

i just made a tif with 5 different vertical grads- some transparent some not.

if you load this into a catalyst layer - you will be able to see some of the blocks are transparent.