A channel is a container in which specific data are stored. For example: the Cyan channel contains the all information about the cyan part of the file. An alpha channel contains all information on a mask that has been added to a file.
This mask is either a saved quickmask or a selection that has been saved. Nothing more, nothing less. So including a mask in a file does not do anything in itself apart from making the file bigger. What you can do is reload the selection at any time, even when you open in another app, or in Photoshop after you've closed the file.

1/ Open your tif and doubleclick on the background in the Layers Palette so as to make it a layer. Accept Layer0 as name (or give another one).
2/ Select the part that you want to keep visible
3/At the bottom of the Layers menu you have several small icons. Choose the second one from the right. The one that has a light circle on a dark background and that says "add a layer mask". Click on this icon, and immediately the pixels you did not select will become transparant.
4/ In your Channels Palette you will now see a new channel called LayerOMask.
5/ Save as tif. Photoshop will ask about including layers. Accept and you will be able to save transparancy.

If you work with Photoshop6, you must set in your preferences that you want to work with advanced tiff.

Now you can open this tiff with everything transparant but your selected pixels in the few programs that accept transparancy in tiff.

X-Press does not. It needs a clipping path because that's the only transparancy that Postscript really knows: a simple hard edged discarding of the information that you did clip. So how do you make a clipping path?

1/ Do as above up to the moment you have made your selection
2/ Open your paths palette and click the icon that's like a circle with a chinese hat on, the one that says make work path from selection. This gives you a dialog box in which you can set the tolerance. Very low values make extremely accurate paths, high values are less accurate. The default is 2. This setting depends on the accuracy you want and the complexity of your path. Try this out, and start with the default setting.
3/ Any information inside the clipping path is opaque, the rest is transparant.
4/ Now double click the path name and give it a good, recognisable name.
5/ Click on the little arrow at the right-hand top of the Paths Palette and choose Clipping Path from the dropdown list.
6/ The flatness value means that you can simplify the path by entering here a higher number. I personally prefer 3 or 4 here.
6/ Save as PhotoshopEPS. Choose whether you want a preview and which quality, choose ASCII or Binary from the dropdownlist
7/ Save.

This should work.

http://www.photoshopgurus.info/forum...ine=1019851685